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  Subjects -> ENGINEERING (Total: 2431 journals)
    - CHEMICAL ENGINEERING (210 journals)
    - CIVIL ENGINEERING (203 journals)
    - ELECTRICAL ENGINEERING (112 journals)
    - ENGINEERING (1271 journals)
    - ENGINEERING MECHANICS AND MATERIALS (402 journals)
    - HYDRAULIC ENGINEERING (57 journals)
    - INDUSTRIAL ENGINEERING (77 journals)
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CIVIL ENGINEERING (203 journals)                  1 2 | Last

Showing 1 - 200 of 203 Journals sorted alphabetically
ACI Structural Journal     Full-text available via subscription   (Followers: 20)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 3)
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 2)
Advances in Civil Engineering     Open Access   (Followers: 39)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 32)
Agregat     Open Access   (Followers: 1)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 34)
Architectural Engineering     Open Access   (Followers: 5)
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 3)
Archives of Civil Engineering     Open Access   (Followers: 12)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 2)
ATBU Journal of Environmental Technology     Open Access   (Followers: 4)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 6)
Baltic Journal of Road and Bridge Engineering     Open Access   (Followers: 1)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 10)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 2)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bioinspired Materials     Open Access   (Followers: 5)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 14)
Building & Management     Open Access   (Followers: 1)
Building and Environment     Hybrid Journal   (Followers: 15)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 14)
Bulletin of Pridniprovsk State Academy of Civil Engineering and Architecture     Open Access   (Followers: 6)
Canadian Journal of Civil Engineering     Hybrid Journal   (Followers: 13)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 6)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 11)
Case Studies in Structural Engineering     Open Access   (Followers: 9)
Cement and Concrete Composites     Hybrid Journal   (Followers: 20)
Challenge Journal of Concrete Research Letters     Open Access   (Followers: 3)
Challenge Journal of Structural Mechanics     Open Access   (Followers: 6)
Change Over Time     Full-text available via subscription   (Followers: 2)
Civil and Environmental Engineering     Open Access   (Followers: 8)
Civil And Environmental Engineering Reports     Open Access   (Followers: 7)
Civil and Environmental Research     Open Access   (Followers: 17)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Architecture     Open Access   (Followers: 22)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 3)
Civil Engineering and Technology     Open Access   (Followers: 12)
Civil Engineering Dimension     Open Access   (Followers: 10)
Civil Engineering Infrastructures Journal     Open Access   (Followers: 1)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 282)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 11)
Computers & Structures     Hybrid Journal   (Followers: 38)
Concrete Research Letters     Open Access   (Followers: 7)
Construction Economics and Building     Open Access   (Followers: 4)
Construction Engineering     Open Access   (Followers: 11)
Construction Management and Economics     Hybrid Journal   (Followers: 21)
Construction Science     Open Access   (Followers: 5)
Constructive Approximation     Hybrid Journal  
Curved and Layered Structures     Open Access   (Followers: 3)
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal   (Followers: 1)
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 17)
Enfoque UTE     Open Access   (Followers: 4)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 7)
Engineering Structures     Hybrid Journal   (Followers: 13)
Engineering Structures and Technologies     Open Access   (Followers: 2)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 10)
Environmental Geotechnics     Hybrid Journal   (Followers: 5)
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 9)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 18)
Frontiers in Built Environment     Open Access  
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Geomaterials     Open Access   (Followers: 3)
Geosystem Engineering     Hybrid Journal   (Followers: 1)
Geotechnik     Hybrid Journal   (Followers: 3)
Géotechnique Letters     Hybrid Journal   (Followers: 7)
GISAP : Technical Sciences, Construction and Architecture     Open Access  
HBRC Journal     Open Access   (Followers: 2)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal  
Indonesian Journal of Urban and Environmental Technology     Open Access  
Indoor and Built Environment     Hybrid Journal   (Followers: 2)
Infrastructure Asset Management     Hybrid Journal   (Followers: 3)
Infrastructures     Open Access  
Ingenio Magno     Open Access   (Followers: 1)
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 30)
International Journal for Service Learning in Engineering     Open Access  
International Journal of 3-D Information Modeling     Full-text available via subscription   (Followers: 3)
International Journal of Advanced Structural Engineering     Open Access   (Followers: 17)
International Journal of Civil, Mechanical and Energy Science     Open Access   (Followers: 2)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 15)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 2)
International Journal of Construction Engineering and Management     Open Access   (Followers: 10)
International Journal of Geo-Engineering     Open Access   (Followers: 3)
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription   (Followers: 4)
International Journal of Masonry Research and Innovation     Hybrid Journal   (Followers: 1)
International Journal of Pavement Research and Technology     Open Access   (Followers: 6)
International Journal of Protective Structures     Hybrid Journal   (Followers: 6)
International Journal of Steel Structures     Hybrid Journal   (Followers: 2)
International Journal of Structural Engineering     Hybrid Journal   (Followers: 8)
International Journal of Structural Integrity     Hybrid Journal   (Followers: 2)
International Journal of Structural Stability and Dynamics     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Built Environment     Open Access   (Followers: 5)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 8)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 7)
International Journal Sustainable Construction & Design     Open Access   (Followers: 1)
Journal of Applied Research in Water and Wastewater     Open Access  
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 14)
Journal of Building Engineering     Hybrid Journal   (Followers: 1)
Journal of Building Materials and Structures     Open Access   (Followers: 2)
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 6)
Journal of Civil Engineering     Open Access  
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 15)
Journal of Civil Engineering and Management     Open Access   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 9)
Journal of Civil Engineering Research     Open Access   (Followers: 7)
Journal of Civil Engineering, Science and Technology     Open Access   (Followers: 1)
Journal of Civil Society     Hybrid Journal   (Followers: 5)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 4)
Journal of Composites     Open Access   (Followers: 78)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 13)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 23)
Journal of Construction Engineering     Open Access   (Followers: 9)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 18)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 6)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 4)
Journal of Fluids and Structures     Hybrid Journal   (Followers: 6)
Journal of Frontiers in Construction Engineering     Open Access   (Followers: 2)
Journal of Green Building     Full-text available via subscription   (Followers: 10)
Journal of Highway and Transportation Research and Development (English Edition)     Full-text available via subscription   (Followers: 14)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 19)
Journal of Legal Affairs and Dispute Resolution in Engineering and Construction     Full-text available via subscription   (Followers: 5)
Journal of Marine Science and Engineering     Open Access   (Followers: 1)
Journal of Materials and Engineering Structures     Open Access   (Followers: 5)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 8)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 9)
Journal of Performance of Constructed Facilities     Full-text available via subscription   (Followers: 3)
Journal of Pipeline Systems Engineering and Practice     Full-text available via subscription   (Followers: 6)
Journal of Rehabilitation in Civil Engineering     Open Access   (Followers: 3)
Journal of Solid Waste Technology and Management     Full-text available via subscription   (Followers: 1)
Journal of Structural Engineering     Full-text available via subscription   (Followers: 36)
Journal of Structural Fire Engineering     Full-text available via subscription   (Followers: 6)
Journal of Structural Mechanics     Open Access  
Journal of Structures     Open Access   (Followers: 4)
Journal of Sustainable Design and Applied Research in Innovative Engineering of the Built Environment     Open Access   (Followers: 1)
Journal of the Civil Engineering Forum     Open Access  
Journal of the South African Institution of Civil Engineering     Open Access   (Followers: 2)
Journal of Water and Environmental Nanotechnology     Open Access  
Journal of Water and Wastewater / Ab va Fazilab     Open Access  
Jurnal Spektran     Open Access   (Followers: 1)
Jurnal Teknik Sipil     Open Access  
Jurnal Teknik Sipil dan Perencanaan     Open Access   (Followers: 1)
Konstruksia     Open Access  
KSCE Journal of Civil Engineering     Hybrid Journal   (Followers: 2)
Latin American Journal of Solids and Structures     Open Access   (Followers: 4)
Materiales de Construcción     Open Access   (Followers: 1)
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 4)
Media Komunikasi Teknik Sipil     Open Access  
Mokslas – Lietuvos ateitis / Science – Future of Lithuania     Open Access  
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 15)
npj Materials Degradation     Open Access  
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 9)
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 3)
Practice Periodical on Structural Design and Construction     Full-text available via subscription   (Followers: 3)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Civil Engineers - Civil Engineering     Hybrid Journal   (Followers: 14)
Proceedings of the Institution of Civil Engineers - Management, Procurement and Law     Hybrid Journal   (Followers: 9)
Proceedings of the Institution of Civil Engineers - Municipal Engineer     Hybrid Journal   (Followers: 2)
Proceedings of the Institution of Civil Engineers - Structures and Buildings     Hybrid Journal   (Followers: 3)
Promet : Traffic &Transportation     Open Access  
Random Structures and Algorithms     Hybrid Journal   (Followers: 5)
Recent Trends In Civil Engineering & Technology     Full-text available via subscription   (Followers: 5)
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 6)
Resilience     Open Access   (Followers: 1)
Revista IBRACON de Estruturas e Materiais     Open Access   (Followers: 1)
Road Materials and Pavement Design     Hybrid Journal   (Followers: 11)
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 5)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 61)
Selected Scientific Papers - Journal of Civil Engineering     Open Access   (Followers: 3)
Slovak Journal of Civil Engineering     Open Access   (Followers: 2)
Soils and foundations     Full-text available via subscription   (Followers: 5)
Steel Construction - Design and Research     Hybrid Journal   (Followers: 3)
Structural and Multidisciplinary Optimization     Hybrid Journal   (Followers: 10)
Structural Concrete     Hybrid Journal   (Followers: 11)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 8)
Structural Engineering International     Full-text available via subscription   (Followers: 11)
Structural Mechanics of Engineering Constructions and Buildings     Open Access   (Followers: 1)
Structural Safety     Hybrid Journal   (Followers: 6)
Structural Survey     Hybrid Journal  
Structure     Full-text available via subscription   (Followers: 24)
Structure and Infrastructure Engineering: Maintenance, Management, Life-Cycle Design and Performance     Hybrid Journal   (Followers: 12)
Structures     Hybrid Journal   (Followers: 1)
Study of Civil Engineering and Architecture     Open Access   (Followers: 10)
Superlattices and Microstructures     Hybrid Journal   (Followers: 2)
Surface Innovations     Hybrid Journal  
Technical Report Civil and Architectural Engineering     Open Access   (Followers: 1)
Teknik     Open Access  
Territorium : Revista Portuguesa de riscos, prevenção e segurança     Open Access  
The IES Journal Part A: Civil & Structural Engineering     Hybrid Journal   (Followers: 6)
The Structural Design of Tall and Special Buildings     Hybrid Journal   (Followers: 5)
Thin Films and Nanostructures     Full-text available via subscription   (Followers: 2)
Thin-Walled Structures     Hybrid Journal   (Followers: 4)
Transactions of the VŠB - Technical University of Ostrava. Construction Series     Open Access   (Followers: 1)
Transportation Geotechnics     Full-text available via subscription   (Followers: 1)
Transportation Infrastructure Geotechnology     Hybrid Journal   (Followers: 8)

        1 2 | Last

Journal Cover
Engineering Structures
Journal Prestige (SJR): 1.69
Citation Impact (citeScore): 3
Number of Followers: 13  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0141-0296
Published by Elsevier Homepage  [3162 journals]
  • The effects of retrofitting RC frames by X-bracing on the seismic
           performance of columns
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): A Rahimi, Mahmoud R. Maheri One of the common method for retrofitting RC frames is to use steel braces. The majority of reported research related to steel bracing of RC frames have highlighted the positive effects of bracing such as improving structural performance, increasing shear capacity, reducing displacements and decreasing drifts. Very little is reported on the possible side effects of the technique on the RC members, particularly those of columns. This papers aims at evaluating, through time history analyses, the behaviour of RC columns before and after retrofitting with steel X-bracing and examining possible complications, increased demands and side effects of such a retrofitting method. The effects on the level of column shear and axial force, as well as, column performance level and low cycle fatigue life are investigated. As a general conclusion, it is found that retrofitting low-rise RC frames with steel X bracing is beneficial to the performance of frame columns in almost every aspect; however, for mid to high-rise frames, the adverse effects of retrofitting, particularly on columns attached to the bracing system, are considerable and should be taken into consideration and if needed, local strengthening of columns should simultaneously be undertaken.
       
  • Optimization of height-wise damper distributions considering practical
           design issues
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Felipe Saitua, Diego Lopez-Garcia, Alexandros A. Taflanidis This paper discusses the optimal height-wise distribution of supplemental viscous dampers in multistorey building structures. Seismic excitation is modeled as stochastic stationary process and response statistics for linear structural systems are obtained through state-space analysis. For nonlinear damper applications statistical linearization is employed to accommodate a similar, state-space formulation. Emphasis is placed on three practical design issues: (i) realistic quantification of damper upfront cost based on damper force capacity rather than on the damping coefficient; (ii) investigation of bracing configuration schemes anchored at non-consecutive floor levels; and (iii) consideration of the cost of column strengthening required to accommodate the additional axial loads due to the supplemental damping system. Five different cost-based objective functions are defined to address these issues and the impact of each of them on the optimal damper distribution is examined in detail. Adjustments for estimation of peak responses when statistical linearization is used are also discussed. The optimal design problem considers the structural performance as a constraint, requiring that a target vibration suppression be achieved through the damper addition. An extension to a multi-objective design optimization is also discussed, incorporating the vibration suppression level as additional objective. The proposed approach is illustrated considering an actual Chilean 26-storey building subjected to an excitation compatible with the Chilean seismic hazard. Results show that damper distributions optimized considering realistic cost assessments are more efficient (with respect to cost-based design objectives) than distributions optimized considering simplified criteria. It is also demonstrated that consideration of practical issues such as column strengthening and feasible damper force capacity have a considerable influence on the optimal distribution. Finally, results also show that further cost reductions can be achieved with braces anchored at non-consecutive floor levels, and that such reductions are consistent with predictions given by approximate analytical expressions.
       
  • Nonlinear dynamic response of steel materials and plain plate systems to
           impact loads: Review and validation
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Maryam Mortazavi, YeongAe Heo A finite element analysis (FEA) model to evaluate the nonlinear effects of severe dynamic loads on engineered structures requires an appropriate constitutive model of the structural material. Although some dynamic constitutive models for steels including mild and high strength steels are specified in offshore design guidelines, their limitations when applied to analysis of severe impact effects haven’t been examined in any details. This paper demonstrates that the structural performance of a steel plate system subjected to impact load of a dropped object is highly sensitive to the adopted dynamic constitutive model using an existing experimental study. The stress-strain response of the plate is strongly dependent on the mechanical and geometrical properties of the steel specimen and the strain rate due to the impact load. While the dynamic constitutive model recommended by Det Norske Veritas (DNV) often overestimates or underestimates the structural response due to impact load, the proposed constitutive model leads to a significant improvement in the DNV recommendations.
       
  • Multitechnical approach for damage assessment and reinforcement of
           buildings located on subsiding areas: Study case of a 7-story RC building
           in Murcia (SE Spain)
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): E. Díaz, P. Robles, R. Tomás The work presented herein proposes a multitechnical methodology for damage assessment and reinforcement of buildings located on areas affected by land subsidence induced by water withdrawal. The proposed methodology is illustrated by a comprehensive damage assessment and subsequent reinforcement of a 7-story reinforced concrete building located in the city of Murcia (SE Spain). Construction took place in the 1980s and the building was severely damaged by differential settlements caused by land subsidence throughout time. The building suffered an important tilting, presenting maximum settlement of 260 mm and a maximum horizontal displacement at the top of the building of 177 mm, which considerably reduced its habitability and security conditions. Damage began to manifest in 1995, coinciding with an intense drought that affected the Murcia area between 1991 and 1995. Average piezometric level decreases of at least 8 m were verified, reaching 10 m in the nearby areas of the building. These piezometric level decreases caused important consolidation settlements that seriously damaged the structure of the building. The proposed multitechnical damage assessment methodology was used to characterize the causes of damage, design reinforcement actions, and carry out subsequent monitoring to guarantee the structural stability of the building.
       
  • OSB sheathed light-frame timber shear walls with strong anchorage
           subjected to vertical load, bending moment, and monotonic lateral load
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Abdollah Sadeghi Marzaleh, Stella Nerbano, Andrea Sebastiani Croce, René Steiger One of the common lateral load resisting systems in multi-story timber buildings in Central Europe are reinforced concrete shear walls. The RC shear walls are not optimal for timber buildings for several reasons such as: (i) the difference in tolerance between concrete and timber construction procedures, (ii) elevated construction time caused by necessary curing of concrete, (iii) moisture of concrete affecting the integrity and mechanical properties of timber, (iv) relatively high shear stiffness resulting in increased forces in seismic design, and (v) eccentricity with regard to applied seismic forces depending on the location of the shear walls. A light-frame timber shear wall (LFTSW) with OSB sheathing stapled to glued-laminated timber framing and strong anchorages has been investigated in this research program to be used as the single lateral load resisting system being located in the perimeter of the building. Results of experiments and numerical calculations showed 20% and 37% increases in shear stiffness and shear resistance, respectively, of the investigated LFTSWs in comparison with established LFTSW configurations. In addition to the conventional racking tests, vertical loads and bending moment were applied to the edge studs in order to study their effect on the in-plane behavior of the investigated LFTSWs. A marginal decrease in shear stiffness and shear resistance was observed due to the vertical load and bending moment applied. The decrease was more significant when applying the vertical loads due to the deformation, to which the staples were exposed, before applying the lateral load. Independent from level and combination of internal forces a ductile behavior was observed experimentally on the investigated LFTSWs, where the failure was governed by ductile displacements in the stapled connection between sheathing and framing.
       
  • Seismic behaviour of connections between prefabricated RC flat slabs and
           square steel tube columns
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Ailin Zhang, Xiaofei Ma, Hao Fang, Junlin Mu, Tingyong Liu Reinforced concrete (RC) flat slab column structure is a typical vertical support system and is often used in regions of moderate seismicity. Additionally, a steel structure is easy to assemble and exhibits good mechanical property, ductility and energy dissipation performance. Thus, this study presents a new type of connection between a prefabricated RC flat slab and square steel tube column. The connection effectively improves seismic performance and stress mechanism and leads to plastic deformation in the cantilever beams that can be replaced after an earthquake. The connection consists of a column base with four cantilever beams, a channel steel connection, and an RC flat slab. A gap connected by four square crossing I-steel cantilever beams is left between the column and channel steel connection, and this forms an opening around the column. An experiment was performed to study the seismic behaviour of the prefabricated slab column connection. The effects of the key parameters including the I-steel web thickness of the cantilever beam and axial compression ratio were investigated. The failure modes, hysteretic curves, and stress–strain curves with respect to relevant components were presented. A numerical simulation verified by the tests was performed to analyse the section stress and bolt forces for making up the test deficiency. The results indicated that the prefabricated slab column connection exhibits a superior seismic performance, thereby leading to earthquake-resilience. Finally, design considerations were presented to guide engineering practice for the proposed prefabricated slab column connection.
       
  • Experimental study on RC beams strengthened with CFRP rod panels
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Akram Jawdhari, Abheetha Peiris, Issam Harik Externally bonded (EB) fiber reinforced polymer (FRP) laminates and fabrics have become a mainstream method for retrofitting and upgrading concrete structures. Nevertheless, when strengthening long-span members or members with limited access, labor, traffic, and equipment demands may hinder the use of continuous EB FRP. The use of carbon FRP (CFRP) rod panels is a recent application of FRP material intended to overcome the above limitations. CFRP rod panels are developed from small diameter rods and are made continuous by means of a finger joint. This study leveraged four-point bending tests to determine whether spliced CFRP rod panels can effectively serve as flexural reinforcement for concrete members. Testing included a control beam and beams strengthened with the following FRP reinforcement layouts: (1) continuous rod panel, (2) spliced panel (two half-length panels with a 150 mm finger joint), (3) spliced panel anchored at ends with CFRP fabric, (4) continuous CFRP laminate, and (5) lap-spliced CFRP laminate system. Beams bonded with either continuous or spliced rod panels failed by concrete cover separation. The beam with spliced and anchored rod panel failed by intermediate crack-induced debonding of the panel. No local debonding or other signs of distress were observed at the finger joint for the two beams strengthened by spliced rod panels. For beams bonded with continuous and lap-spliced CFRP laminates, the failure was by laminate debonding. Compared to a control specimen, the maximum load increase of the strengthened beams was as follows: 112% for the continuous rod panel; 106% for spliced rod panel; 158% for the spliced/anchored rod panel; 49% for continuous laminate; and 31.8% for lap-spliced laminate.Graphical abstractPerformance of RC beams strengthened with full-length and spliced CFRP laminate and CRP.Graphical abstract for this article
       
  • Analytical model for shear strength estimation of reinforced concrete
           beam-column joints
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Leonardo M. Massone, Gonzalo N. Orrego A model capable of predicting the shear response of beam-column joints subjected to seismic actions is presented. The analytical model, originally developed for walls and based on a simple physical formulation, is adapted. It considers mean stress and strain fields based on a reinforced concrete panel representing the joint, under the assumption that the principal concrete stress and principal strain directions coincide. Simple constitutive material laws are considered for concrete and steel. To estimate the shear capacity, the model satisfies the equilibrium in the longitudinal (vertical) direction. In order to analyze the accuracy of the model, a database integrated by 92 tests of exterior and interior beam-column joints is collected from the literature. Noting that the original model does not consider the effect of confinement product of adjacent elements to the connection, this effect is introduced through factors that reduce the values of the longitudinal and transverse strain used to calibrate the angle of the strut. In addition, the contribution of the transverse reinforcement in the capacity of the element is included. These modifications together with the influence of the boundary reinforcement, yields a good strength estimate for exterior and interior joints that fail in shear. When comparing with other models from the literature, it is observed that the proposed model provides one of the best correlations.
       
  • Advances in the derivation of fragility functions for the development of
           risk-targeted hazard maps
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Luís Martins, Vítor Silva, Paolo Bazzurro, Mário Marques Risk-targeted hazard assessment aims at estimating the design ground shaking that leads to a uniform distribution of the collapse probability of buildings within a given region. An essential aspect of this methodology relies on the definition of the relationship between the collapse probability of buildings designed according to modern seismic regulations and the considered design ground motion. This study adds to previous research on the topic of seismic risk-targeted hazard assessment by investigating how the collapse probability varies with the design level of ground motion, and how this variability influences the resulting seismic risk across Europe. A large number of structures designed according to the most recent seismic regulation in Europe have been analysed. These structures were designed for increasing levels of peak ground acceleration ranging from values close to zero (i.e. buildings located in regions with very low seismic hazard) up to 0.40 g (i.e. moderate to high seismic hazard). Each structure was modelled as a tri-dimensional finite element model, and tested against a set of ground motion records using nonlinear dynamic analyses. Several fragility functions were derived for yielding and collapse damage states, and combined with the seismic hazard curves from the European project SHARE to calculate the spatial distribution of earthquake risk across Europe.
       
  • Multi-unit rolling isolation system arrays: Analytical model and
           sensitivity analysis
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): C.D. Casey, P.S. Harvey, W. Song Rolling isolation systems (RISs) have been used extensively to protect vibration-sensitive equipment, such as server cabinets, from earthquake-induced floor motions. These systems are commonly installed in multi-unit arrays to isolate multiple cabinets from harsh floor motions. The mathematical model presented in this paper is an extension of an experimentally-validated model for a single-unit RIS and is amenable to an arbitrary number of isolated cabinets. The proposed model is first compared to free response tests and is then validated with forced response tests using a synthetic waveform representative of earthquake-induced floor motions. An extensive numerical parameter study using the proposed model is carried out to assess the influence of the number of isolated cabinets, as well as mass eccentricity, on the seismic isolation performance of these systems. Through an incremental dynamic analysis it is shown that systems with more cabinets are less prone to impacts, indicating better performance. Rotations produced in the presence of mass eccentricity may induce premature impacts transverse to the loading direction diminishing these systems’ performance.
       
  • Gusset design considering buckling forces in frame and brace action
           directions: Test and finite element analysis of a self-centering braced
           frame for verification
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Chung-Che Chou, Alexis Rafael Ovalle Beato A steel dual-core self-centering brace (DC-SCB) has been developed to combine both energy dissipation and self-centering properties into a single member for seismic resistance. A strong gusset-weak brace design assures the seismic response of the DC-SCB in earthquakes. In this work, in-plane cyclic tests and finite element analyses were conducted on single story steel frames with the DC-SCB to investigate the performance of corner gusset plates due to the brace axial force (which acts in the direction of the brace) combined with the force from the frame action (which acts in a direction near perpendicular to the brace axial force). Different configurations of gusset plates were used for analyses to develop a design method to consider effects from brace forces and frame action forces. The yielding and buckling forces of a gusset plate in the frame action direction are verified based on a proposed column strip model and buckling coefficient varied with gusset thickness. It is shown to be consistent with the behavior from the tests and finite element analyses with errors in strength of up to 13% for the range of gusset configurations considered.
       
  • Using dynamic measurements to detect and locate ruptured cables on a
           tensegrity structure
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Ann C. Sychterz, Ian F.C. Smith Tensegrity structures are cable-strut systems held in equilibrium due to self-stress. There is potential for damage tolerance when they are kinematically redundant. In this paper, detection and location of a ruptured cable in a deployable tensegrity footbridge are studied through monitoring changes in dynamic behavior. Position values and axial load values of elements are measured before, during, and after a cable breakage. Free and forced-vibration-induced dynamic behavior of the tensegrity structure are characterized in the state of deployment (one half of the structure) and in-service (full structure). Examination of ambient vibrations for the half structure and forced vibrations for the full structure successfully led to detection of ruptured cables. Exclusion of possible damage cases for location using measurements effectively reduces the number of candidate cases when using nodal displacement measurements. Correlation methods using strain measurements are also successful to locate a ruptured cable. These methods reveal the potential for self-diagnosis of complex sensed structures.
       
  • Displacement and mixed fibre beam elements for modelling of slender
           reinforced concrete structures under cyclic loads
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Samer Sabry F. Mehanny Gendy, Ashraf Ayoub In this paper, two fibre-based beam elements with enhanced capabilities to consider large displacements and rotations of slender reinforced concrete members are developed. Fibre beam elements were comprehensively used before to model the behaviour of different structural systems with great accuracy. To upsurge the use of the fibre beam elements in modelling complex reinforced concrete (RC) systems such as slender walls and columns, the elements are improved by including the second order effect. Available research from the literature related to large displacements focused mainly on modelling steel and composite members due to the limitations in their material model behaviour. Conversely, the newly developed elements introduced in this paper can precisely model RC members by accounting for their more complex nonlinear material behaviour under reversed cyclic loads. The first element is formulated using a displacement formulation, while the second element is based on a mixed approach that is computationally more complicated but numerically more efficient. Further, the adopted concrete constitutive law accounts for the effect of compression post-peak softening as well as tension stiffening and degradation under cyclic loads. Several correlation studies are presented to highlight the efficiency of the new elements in modelling slender RC structures.
       
  • Failure modes prediction of masonry voussoir arches on moving supports
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Stefano Galassi, Giulia Misseri, Luisa Rovero, Giacomo Tempesta This paper reports numerical and experimental investigations carried out to analyse vulnerability of masonry voussoir arches when subjected to soil settlement. A novel numerical procedure aimed at predicting collapse layout and limit settlement is here presented. To identify the location of the three hinges that open when the settlement triggers, a procedure based on combinatorial analysis is exploited together with both static and kinematic analysis. In the framework of finite displacements, the limit settlement of an arch is also found checking equilibrium at every step increase of the settlement.Good agreement is found between experiment results provided by reduced scale arch models, made of blocks of PVC and subjected to a horizontal or vertical settlement of the left support, and numerical predictions.Furthermore, a sensitivity analysis has been carried out in order to assess the trend of the limit settlement in relation with ring thickness and number of blocks. Results show that the limit settlement for spreading supports is independent from the number of blocks for a given angle of embrace.
       
  • Fatigue repair of underwater navigation steel structures using Carbon
           Fiber Reinforced Polymer (CFRP)
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Guillermo A. Riveros, Hussam Mahmoud, Christine M. Lozano The nation’s Steel Hydraulic Structures (SHS) have significant deterioration caused by the effects of complex phenomena including corrosion and fatigue cracking caused by mixed mode loading. Current methods of repair of SHS, adopted primarily from the bridge engineering industry, have proven ineffective because they were developed for Mode 1 loading (tension) only. Various studies have been carried out to assess the use of CFRP for the rehabilitation of the aging and deteriorated infrastructure systems in the United States, however no research has been conducted on submerged steel structures. This paper presents the evaluation and implementation of an innovative retrofit method of CFRP to repair and strengthen the strut arms of a tainter valve. The evaluation of the retrofit method required a Fitness-for-Service fatigue assessment followed by a Finite Element Analysis (FEA) of the tainter valve with and without the retrofit method. Finally, the article presents the installation procedures used to install the CFRP retrofit and describes the advantages of the innovative repair techniques resulting in two to four folds increase of fatigue life.
       
  • Eccentric-wing flutter stabilizer for bridges – Analysis, tests,
           design, and costs
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): U. Starossek, T. Ferenczi, J. Priebe A device is presented that aims at preventing bridge flutter. It consists of wings positioned along the sides of, and fixed to, the bridge deck. Flutter suppression effectiveness is high provided the lateral eccentricity of the wings is large. It is a passive aerodynamic device that is presumably more cost-efficient than other passive measures or devices. Moreover, it does not contain moving parts. This is an advantage over devices with moving parts, which meet resistance due to reliability and durability concerns. Wind-tunnel tests were performed in which the flutter speed of a bridge deck sectional model without wings and with wings mounted in various configurations was measured. The experimental results are presented and compared with the results of flutter analyses using finite aeroelastic beam elements. Using the analytical approach, also the effect of the distribution of the wings along the length of a bridge was studied to optimize this distribution. Preliminary design studies for the wings and their support structures as well as quantity and cost estimates are presented. For a representative example bridge and wing configuration, an increase of 22% of flutter speed is reached at a cost increase of 2.5%.
       
  • Peak factor statistics of wind effects for hyperbolic paraboloid roofs
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Fabio Rizzo, Michele Barbato, Vincenzo Sepe This paper investigates the statistics of the pressure coefficients and their peak factors in hyperbolic paraboloid roofs that are commonly used in tensile structures. The experimental peak factor statistics, estimated using pressure coefficient time histories experimentally measured in wind tunnel tests, were compared with the corresponding peak factor statistics estimated through the use of six analytical models available in the literature, namely the Davenport, classical Hermite, revised Hermite, modified Hermite, Translated-Peak-Process (TPP), and Liu’s models. The basic assumption of the TPP model, i.e., that the pressure coefficient local peaks follow a Weibull distribution, was validated and was used to estimate analytically the peak factors’ quantiles. Different time history durations and different error measures were also considered. The non-Gaussian properties of the pressure coefficient processes were characterized at different roof locations for different wind angles of attack. It was found that: (1) the region of non-Gaussianity is significantly affected by the wind angle; (2) as expected, the Davenport model underestimates the peak factor mean and standard deviation in regions of high non-Gaussianity; (3) the modified Hermite model provides the best estimates overall of the peak factor mean; and (4) the TPP model provides the best estimates overall of the peak factor standard deviation. In addition, the modified root mean squared error was found to provide the most reliable assessment of the analytical models’ accuracy among the different error measures considered in this study.
       
  • Evaluation of the flexural strength and serviceability of concrete beams
           reinforced with different types of GFRP bars
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Amr El-Nemr, Ehab A. Ahmed, Adel El-Safty, Brahim Benmokrane The current available glass-fiber-reinforced polymer (GFRP) bars have a modulus of elasticity ranges from 40 to 60 GPa in accordance with CSA S807-10 Canadian standard. The surface profile of GFRP bars, however, can be smooth, sand-coated, deformed, grooved, or ribbed. This study aimed at investigating the flexural behavior and serviceability performance of concrete beams reinforced with different types of GFRP bars. The test parameters were: (i) modulus of elasticity (46.4–69.3 GPa); (ii) surface profile (sand-coated and helically-grooved), and (iii) reinforcement ratio. The study included testing of 17 full-scale beams measuring 4,250 mm long × 200 mm wide × 400 mm deep reinforced with GFRP bars. The test results are presented and discussed in terms of deflection, crack width, strain, and load-carrying capacity. The cracking behavior of the tested beams tends to confirm that sand-coating of GFRP bars enhances the bond performance in concrete more than the helically-grooved profile. The curvature limit of 0.005/d seems to be feasible in controlling the serviceability of GFRP-reinforced concrete (GFRP-RC) beams. In addition, ACI 440.1R-06 and ACI 440.1R-15 underestimated the deflection, while ISIS M-03 and CSA S806-12 provided conservative deflection values at 0.30 of nominal moment capacity, Mn.
       
  • SSI effects on seismic demand of reinforced concrete moment resisting
           frames
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Romeo Tomeo, Dimitris Pitilakis, Antonio Bilotta, Emidio Nigro We present the results of nonlinear dynamic analyses performed on reinforced concrete (RC) moment resisting frames (MRFs). The analyses were performed considering SSI by means of both a plane-strain soil-structure finite element model approach and a structure-on-springs approach. The results show that the complete FE model approach may produce significant differences in the evaluation of the seismic demand, in terms of maximum inter-storey drift, with respect to the fixed-base structure and to the structure-on-springs approach, mainly because of the different incorporation of the damping in the two modeling approaches.Differences in the soil properties, the seismic design level of the structures and the modeling technique of SSI effects are reflected as reduction in the seismic demand with respect to a fixed-base model, up to 50% in maximum inter-story drift ratio and up to 20% in maximum base shear for the complete FE model and up to 20% in both maximum base shear and maximum inter-story drift ratio for the simplified BNWF model.
       
  • Out-of-plane structural identification of a masonry infill wall inside
           beam-column RC frames
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Alessandra De Angelis, Maria Rosaria Pecce Field observations after seismic events have shown that out-of-plane collapses are one of the predominant modes of infill masonry wall failure leading to life-safety hazards. This type of mechanism depends on the geometrical and mechanical features of the structure, but it is substantially affected by the constraints along the structural frame. However, the actual boundary conditions are very difficult to define, especially in the case of an existing building, for which information is lacking, a visual screening can be inefficient, and deterioration may have occurred due to the design conditions.In this paper, a procedure for the structural identification of the out-of-plane behaviour of infill masonry walls using a simple and cost effective innovative procedure based on an in situ experimental dynamic test and a consequent process of updating is proposed. The procedure, composed of the in situ test and the updating of the numerical model, was implemented for a case study to confirm that it is effective in defining the mechanical characteristics of the masonry, the absence of collaboration between the two brick leaves of the infill wall, and the out-of-plane constraints along the perimeter.
       
  • Mapping deformations and inferring movements of masonry arch bridges using
           point cloud data
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): C. Ye, S. Acikgoz, S. Pendrigh, E. Riley, M.J. DeJong Many historic masonry arch bridges experience damage due to support movements during their lifetime. This damage may influence the performance of the bridge and reduce its load carrying capacity. This paper proposes a new method to quantify past support movements by investigating distortions in bridge geometry. In this method, the bridge geometry is recorded in point cloud format and segmented into different structural components (e.g. 3D piers and barrels or 2D pier and barrel cross-sections). The geometry of each component is investigated further by fitting primitive shapes (e.g. 3D planes and cylinders or 2D lines and arcs) which represent the design intent. The discrepancy between these fitted shapes and the point clouds reveals a characteristic distortion signature. This signature is compared with theoretical distortion traces, which are obtained from kinematical analyses of the arch subjected to a range of support movements. The most likely support movement scenarios identified from these comparisons are then validated with visual indications of damage, such as crack location and size, and other geometric quantities, such as the change of the bedding joint elevations along the bridge. The proposed technique is applied to two masonry rail viaducts in the UK, which demonstrate different evidence of damage. Using the proposed method, past support movements of both bridges, which led to the observed damage, are inferred.
       
  • Numerical investigation of non-linear equivalent-frame models for regular
           masonry walls
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Rossella Siano, Pere Roca, Guido Camata, Luca Pelà, Vincenzo Sepe, Enrico Spacone, Massimo Petracca The accuracy of the Equivalent Frame Method (EFM) in modelling the seismic non-linear behaviour of unreinforced masonry (URM) buildings is investigated for regular walls (i.e. walls with regular openings’ distribution) with different pier-to-spandrel geometrical relations. The developed EFM is composed of pier and spandrel elements with spread plasticity to simulate the flexural behaviour and lumped plasticity to simulate the shear behaviour. The investigation focuses on checking, by means of comparison with Finite Element Model (FEM) assumed as reference, the applicability of EFM to existing buildings. These structures are often characterized by geometrical schemes difficult to be represented by ideal frames. To point out the role of the geometrical configuration, the numerical results provided by the two modelling approaches are compared for different representative cases of regular walls characterized by pier-spandrel configurations rather typical in existing URM buildings. In addition to the innovative EFM approach, based on a fiber discretized beam element, also a more traditional approach, based on beam elements with lumped plasticity, is included in the comparative study. The two different EFM approaches were implemented in the software Midas GEN © [44], while an open source software was used to implement the FEM (Kratos Multiphysics [59–60]). All the models were used to perform static non-linear analyses under equivalent loading and boundary conditions.The evaluation of EFM and FEM is derived from a comparative simulation of a two-storey URM wall experimentally tested by other researchers. Two alternative approaches are assumed for the definition of piers’ effective heights in the EFM, i.e. the models proposed by Dolce [1] and Augenti [2]. The results demonstrate that remarkable differences may be detected in EFM and FEM predictions of the shear capacity and damage mechanisms as a function of pier-spandrel geometrical configurations. This result highlights the need for a cautious application of EFM to existing URM structures.
       
  • Structural behaviour and design of elliptical high-strength
           concrete-filled steel tubular short compression members
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): M.F. Hassanein, V.I. Patel, A.M. El Hadidy, H. Al Abadi, Mohamed Elchalakani Elliptical concrete-filled steel tubular (CFST) columns have recently attracted significant attention because of their increased strength and stiffness compared with empty elliptical hollow sections (EHSs). As with any new cross-section, there are still many aspects to be investigated to allow for its inclusion in different design specifications. Based on literature survey, this paper investigates the elliptical CFST columns which are filled with high-strength concrete (HSC). Numerical investigations into the structural behaviour of the elliptical CFST columns subjected to pure axial compression and eccentric loading have been performed using the general purpose commercial finite element (FE) software, Abaqus. The validity of the current FE models is examined by comparing their outcomes with those test results in literature. Then, parametric studies are performed considering three main parameters, namely the slenderness of the EHS, the steel yield strength and the concrete compressive strength. This is followed by a discussion of the results, showing in detail the characteristics of their load-strain responses. A comparison of the ultimate strengths with the existing design models is then considered, from which it is found that improved design model could be suggested to save additional weight and reach an optimum design. Hence, a new design formula is presented at the end which considers the effective confined concrete strength. Overall, this investigation expands the available engineering knowledge and assists in utilising the HSC, currently used in a wide range of applications, with the elliptical CFST columns with their favourable aesthetical and structural characteristics.
       
  • Calibrations of numerical models by experimental impact tests using scaled
           steel boxes
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): J.J. Wang, Y.C. Song, W. Wang, J. Li The bridge piers located in navigation waterways are susceptible to vessel impact. In order to protect bridge piers from vessel impact, different kinds of protective structures have been developed. As one of such protective structures, the flexible anti-collision device with a steel outer periphery surrounding the bridge pier is frequently used in bridge designs against vessel impact. The mechanical properties of such steel anti-collision devices subjected to vessel impact loadings often need to be investigated by means of finite-element simulations using numerical models, the accuracy of which is critical. The objective of this paper is to conduct a group of hammer impact tests using scaled steel boxes and use the experimental results to validate the numerical models. Such numerical models with sufficient prediction accuracy can be further extended for applications to the design of the steel anti-collision devices subjected to vessel impact loadings.
       
  • Behavior and design of high-strength circular reinforced concrete columns
           subjected to axial compression
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Rami Eid, Konstantin Kovler, Israel David, Waseem Khoury, Shay Miller High-strength concrete (HSC) can be of great interest for the construction of lower-stories reinforced-concrete (RC) columns in high-rise buildings. This superior material can reduce the dimensions of the columns, and therefore, can be considered as a more advantageous material than normal-strength concrete (NSC). To compensate for its higher brittleness nature, the confinement reinforcement ratio required for HSC has to be larger than that required for NSC. The aim of this study is to examine the confinement transverse steel reinforcement amounts required for HSC circular columns part of high-rise buildings. The study first compares the confinement reinforcement requirements given by leading standards. Following the comparative research, an experimental study on six HSC columns subjected to axial loading was performed. The results show that in terms of axial capacity, it is recommended to further examine the concrete strength reduction factor and that it is more reasonable to consider a value lower than 0.85 for the design of HSC columns. Moreover, in terms of confinement and ductility, the recommended volumetric transverse steel reinforcement ratio for HSC circular columns not considered as part of the seismic-force-resisting system (SFRS), can be based on the ACI standard requirement and equal to half of the maximum specified volumetric transverse steel reinforcement ratio required for HSC columns considered as part of the SFRS.
       
  • Shape optimization of railroad vibration energy harvester for structural
           robustness and power generation performance
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Saman Nezami, Soobum Lee, Jiwon Jin, Ki-Weon Kang This paper presents design optimization of a stiffness component in a vibration energy harvester – diaphragm spring – for structural robustness and reliable power generation in railroad vehicle monitoring applications. Power generation is usually sufficient under the high impact loading of railroad operating conditions, but a highly durable harvester design has been a challenging issue. This paper performs a practical shape optimization of the diaphragm spring considering realistic vibrational loading conditions. In this study, we build the power spectrum density (PSD) of acceleration loading based on a railroad system design standard and use it for maximum stress estimation. A separate electromagnetic analysis has been conducted to determine the vibrational amplitude for the required power generation. A new conceptual diaphragm spring model has been chosen to minimize any unnecessary parasitic motion that could cause asymmetric spring deformation and excessive stress. The shape optimization on the new conceptual spring model has been conducted to obtain the new design that reduces the magnitude of stress concentration by 16% while satisfying the required vibration amplitude for energy harvesting.
       
  • Circuit nonlinearity effect on the performance of an electromagnetic
           energy harvester-structure system
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Cheng Ning Loong, Chih-Chen Chang, Elias G. Dimitrakopoulos Scavenging energy from structural vibration requires an efficient energy harvesting circuit which could introduce nonlinearity into the harvester-structure system. This study examines the performance of a linear structure equipped with an Electromagnetic (EM) energy harvester connected to a nonlinear standard energy harvesting circuit (SEHC) consisting of a full-wave bridge rectifier and a capacitor in parallel with a resistor. To facilitate the understanding of the nonlinear circuit effect on the behavior of the coupled harvester-structure system under sinusoidal excitation, a first-order harmonic balance approximation method is employed. Numerical simulation and experimental study are conducted to validate the accuracy of the proposed approximation method. Results suggest that the blockage effect of diodes in the bridge rectifier in the SEHC should be reduced by using diodes with small voltage drop value or by designing an EM energy harvester with large electromechanical coupling coefficient to improve the vibration mitigation performance and to enhance the optimal energy harvesting capability of the EM energy harvester. Results also show that circuit nonlinearity should be considered in order to estimate the response of the system accurately.
       
  • Free vibration of axially functionally graded beams using the asymptotic
           development method
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Dongxing Cao, Yanhui Gao, Minghui Yao, Wei Zhang Axially functionally graded (AFG) beams, with variable coefficients in the governing equation, are a novel class of composites structures that have continuous variations in material properties from one component to another. In this paper, the asymptotic development method (ADM) is utilized to investigate the free vibration of uniform AFG beams with different boundary conditions. By decomposing the variable flexural stiffness and mass per unit length into reference invariant parts and variant parts, perturbation theory is introduced to obtain an approximate formula of the natural frequencies of the uniform AFG beams. The numerical results of the proposed method are confirmed by comparing the obtained results with those obtained via finite element analysis and the published literature results, the comparison reveals the proposed method yields an accurate estimate of the first three order natural frequencies of the AFG beam. Moreover, the influences of the gradient parameter and support conditions on the first three natural frequencies are discussed. The proposed analytical method is simple and efficient and can be used to conveniently analyze uniform AFG beams with arbitrary changes in the material properties along the axial direction.
       
  • Push-out behavior of headed shear studs welded on thin plates and embedded
           in UHPC
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Dominic Kruszewski, Kay Wille, Arash E. Zaghi A novel repair method has been developed for steel bridge girders with corrosion damage at the ends. The concept involves welding headed studs to the intact portion of the web plate and encasing them in Ultra-High Performance Concrete (UHPC). This creates a bearing force transfer mechanism to bypass the corroded web plate. Since the headed studs play a crucial role in transferring the shear forces to the UHPC, a careful study is needed to validate their shear capacity when welded to thin web plates typical of steel girders. This paper presents the experimental results from a series of push-out specimens with studs welded to a 9.5-mm thick plate extracted from an old steel bridge. The objective of the study is to understand the influence of design parameters including diameter, spacing and layout on the capacity and failure mechanism of headed studs in UHPC. The experimental results indicate that the capacity was consistently higher than that predicted by design codes such as AASHTO or Eurocode-4. The results show that studs with significantly smaller spacing than what is typically used in practice reach their full capacity. This enables placement of many studs in small regions of the web as may be required in this repair design. The consistent mode of failure was shear rupture at the stud shank. Based on these results, an existing capacity formulation was refined for headed studs embedded in UHPC.
       
  • The importance of correlation among flutter derivatives for the
           reliability based optimum design of suspension bridges
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Ibuki Kusano, Aitor Baldomir, José Ángel Jurado, Santiago Hernández The design of long-span bridges is constrained by the uncertainty in the evaluation of flutter velocity. Among all the elements that take part in the flutter assessment, the uncertainty level in experimentally obtained flutter derivatives has the most impact. It is therefore important in the evaluation of flutter velocity to assess the uncertainty which is associated with the adopted experimental method for flutter derivatives. By using a method of coupled motion only to identify eight flutter derivations simultaneously, it is also essential to consider correlations among the points that define the full set of flutter derivatives since they are not independent from one another. In this research, an experimental campaign was carried out to obtain the statistical information of flutter derivatives and to assemble the correlation matrix. Several cases of reliability analyses were performed to illustrate the importance of considering correlation among random variables as well as the significance of uncertainty level in flutter derivatives on bridge flutter failure. Moreover, a study of Reliability Based Design Optimization (RBDO) was carried out to see the influence of correlations among flutter derivatives on the optimum designs. The RBDO of a suspension bridge was performed under probabilistic flutter constraint using Reliability Index Approach (RIA) method, and this methodology was applied to the Great Belt East Bridge.
       
  • Flexural strength and stiffness of block-out connections for steel columns
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Paul W. Richards, Nick V. Barnwell, Joshua E. Tryon, Ashley L. Sadler In many steel buildings, the columns are attached to the foundation through a block-out in the slab-on-grade that is later filled with unreinforced concrete. Engineers typically neglect the block-out concrete in design, effectively treating block-out connections as exposed connections with pinned behavior. Quantifying the flexural strength and stiffness of block-out connections is helpful for determining moment demands on foundations and may lead to more economical connections at the base of steel moment frames. Eight experimental specimens (two-thirds scale) were subjected to lateral loads to investigate the effects of column size, block-out thickness, and load orientation on connection flexural strength and stiffness. The observed flexural strengths were 1.4–2.7 times greater than those calculated neglecting the block-out concrete, because the block-out concrete effectively thickened and expanded the column base plate. A simple method was developed that predicted the flexural strength of the block-out connections to within 10 percent. The effective flexural stiffness at the base of the columns that were tested could be reasonably estimated using a model that combines the theory of beams on elastic foundations with a base rotational spring.
       
  • Downtime estimation and analysis of lifelines after an earthquake
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Omar Kammouh, Gian Paolo Cimellaro, Stephen A. Mahin This paper provides an empirical probabilistic model for estimating the downtime of lifelines following earthquakes. Generally, the downtime of infrastructure varies according to several factors, including the characteristics of the exposed structure, the earthquake intensity, and the amount of available human resources. Having so many variables makes the process of estimating the downtime even harder. Therefore, it is necessary to have a simple and practical model to estimate the downtime of infrastructure systems. To do so, a large database has been collected from literature, which includes damage data for many earthquakes that took place in the last century. The database has been used to create restoration curves for four types of lifelines: Water distribution network, Gas network, Power system, and Telecommunication network. Different restoration curves have been developed based on several criteria, such as the earthquake magnitude, development level of the affected country, and countries with enough data. The restoration curves have been presented in terms of probability of recovery and time; the longer is the time after the disaster, the higher is the probability of the infrastructure to recover its functions.
       
  • Nonlinear structural dynamic analysis by a stabilized central difference
           method
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Delfim Soares, Georg Großeholz In this work, a simple stabilized central difference technique is discussed, to analyse nonlinear models. The proposed technique is unconditionally stable for linear systems and it provides enhanced stability features for nonlinear applications. The proposed method stands as a direct single step procedure, avoiding any iterative computations when solving nonlinear models; thus, it is very efficient. In addition, it is extremely accurate, providing much reduced period elongation and amplitude decay errors, compared to standard methods. The present work also introduces a criterion for updating the nonlinear system matrices, significantly reducing the computational complexity of the simulation and enhancing the efficiency of the technique. Numerical results are presented along the manuscript, illustrating the performance and accuracy of the proposed methodology.
       
  • Seismic-resistant self-centering rocking core system with buckling
           restrained columns
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Felix C. Blebo, David A. Roke Conventional concentrically braced frame (CBF) systems have limited drift capacity prior to brace buckling, and related damage leads to deterioration in strength and stiffness. CBFs are also susceptible to soft-story failure. A pin-supported self-centering rocking core system with buckling-restrained columns (SCRC-BRC) is being developed to provide significant drift capacity while limiting damage due to residual drift and soft-story mechanisms.The SCRC-BRC system consists of beams, columns, and braces branching off a central column, with buckling restrained columns (BRCs) incorporated into the system at the first story external column positions. The BRCs and friction generated at lateral-load bearings at each floor level are used to dissipate energy to reduce the overall seismic response of the SCRC-BRC system. Vertically-aligned post-tensioning bars provide additional overturning moment resistance and aid in self-centering the system to eliminate residual drift. The pin support condition at the base of the central column and the lateral stiffness of the system enable it to exhibit a nearly uniform inter-story drift distribution.In this study, the suite of 44 DBE-level ground motions used in FEMA P695 is numerically applied to several SCRC- BRCs to demonstrate the seismic performance of the system. The results show that the SCRC-BRC system has a nearly uniform inter-story drift response, high ductility, and a high energy dissipation capacity, and is an effective seismic-resistant system.
       
  • A softened membrane model for composite box-girders with corrugated steel
           webs under pure torsion
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Kongjian Shen, Shui Wan, Y.L. Mo, Xiayuan Li, Aiming Song The softened membrane model for torsion (SMMT), formerly developed for the torsional analysis of reinforced concrete (RC) members, has the capability of modeling the biaxial strains of concrete with Poisson effect, the tension stiffening effect of concrete and the contribution of concrete in shear. It is extended to the composite box-girders with corrugated steel webs under pure torsion in this study. The extended SMMT for RC composite box-girders with corrugated steel webs incorporates the contribution of corrugated steel webs into the SMMT for RC members by applying the assumption of shear strain relations between concrete slabs and corrugated steel webs. Moreover, the thickness of shear flow zone in concrete slabs is reasonably corrected. Besides, the modifications of equilibrium equations and convergence criteria are conducted for the prestressed concrete (PC) composite box-girders with corrugated steel webs. The modified SMMT for RC/PC composite box-girders with corrugated steel webs is able to predict the overall torsional behavior, including the torque-twist curve and the smeared shear strains in concrete slabs and corrugated steel webs, as well as any other related variables. The accuracy and superiority of the proposed model are verified by comparing the theoretical predictions from the SMMT with the experimental results and the predictions from existing model.
       
  • Simple cross-laminated timber shear connections with spatially arranged
           screws
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Cristiano Loss, Afrin Hossain, Thomas Tannert This paper presents an experimental study to evaluate the use of spatially arranged self-tapping screws (STS) as shear connections for cross-laminated timber panels. Specifically, simple butt joints combined with crossed STS with different inclinations were investigated under quasi-static monotonic and reversed-cyclic loadings. The influence of the number and angle of insertion of screws, screws characteristics, friction and loading on the joint performance was explored. The yield load, load-carrying capacity and related slips, elastic stiffness, and ductility were evaluated considering two groups of tests performed on a total of 63 specimens of different size. Performance of connections with respect to the energy dissipation and loss of strength under cyclic loads was also investigated. It was shown that the spatial insertion angle of screws plays a key role in the performance of joints, not only because it relates to the shank to grain angle, but also because it affects the amount of wood involved in the bearing mechanism. Design models of STS connections are presented and discussed, and the test results are compared against analytical predictions. While good agreement for load-carrying capacity was obtained, the existing stiffness model seems less adequate with a consistent overestimation.
       
  • Development of the multiple tenon timber connection based on experimental
           studies and FE simulation
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Timo Claus, Werner Seim This paper describes the development of the multiple tenon connection from the basic idea to an optimised timber connection. Based on the promising results of a first series of experimental testing, a finite element model considering different failure modes was developed to simulate the load-bearing behaviour of a four-tenon connection. The shape of the multiple tenons and the geometrical position was studied to compare the varying ultimate loads depending on different geometrical parameters. Based on these relations, a second experimental series was developed with an improved design. The results show significantly higher load capacities compared to the results of the first test series. Different possibilities of additional reinforcement have been studied. In comparison to existing form-fitting connections, multiple tenons exhibit a remarkable increase of load-bearing capacity together with reduced scattering of test results. Two-dimensional finite element simulations supported the design optimisation of wood-to-wood connections in a very efficient way.
       
  • Wind resistant size optimization of geometrically nonlinear lattice
           structures using a modified optimality criterion method
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Ji-Yang Fu, Ben-Gang Wu, Jiu-Rong Wu, Ting Deng, Yong-Lin Pi, Zhuang-Ning Xie Lattice structures normally have slender members and light weight, high flexibility and small damping ratios. Hence, their structural behavior may be affected by the geometric nonlinearity and they are prone to large displacements and safety issues due to wind loads. Optimal design of such nonlinear and flexible structures is difficult and complicated. This paper presents an automatic optimizing flow for the integrated wind-induced response analysis and wind-resistant optimal design of linear and non-linear lattice structures based on the modified Optimality Criterion (OC) algorithm. The method for structural dynamic analysis and wind-induced response of lattice structure is developed by combining Proper Orthogonal Decomposition (POD) with Load Dependent Ritz (LDR) vector method, together with the Harmonic Excitation Method (HEM) and Load Response Correlation (LRC) method. Meanwhile the quadratic programming method is used to evaluate the Lagrange multipliers in the modified optimality criterion method. Based on the derived design sensitivity analysis results for the nodal displacements, element stresses and nonlinear critical load factor of linear and nonlinear space frame structures in a companion paper, an automatic optimizing flow is then established by adopting the Application Programming Interface (API) of SAP2000 to integrate the wind-induced response, design sensitivity analysis and wind-resistant optimal design of space frame structural system. The proposed automatic optimizing flow is then applied to the optimized process of a lattice structure under dynamic wind loading. It is found that for the lattice structure, the geometric non-linear analysis and the constraint of nonlinear critical load factor need to be considered in their optimization, meanwhile updating on the time-history of wind loads and Equivalent Static Wind Loads (ESWL) is necessary as result of the variations in the design member size during the optimization process. It is also found that the maximum displacement constraint is the most important factor in the optimization of the lattice structure and maximum stress of structural elements are normally found to be inactive constraints during the optimization procedure. In the case that a low limit for the maximum displacement is pre-set, the nonlinear critical load factor becomes the important constraint. Optimized results from this study would be helpful to those involved in wind resistant analysis and optimization design research for such lattice structures.
       
  • Stability analysis of oil-conveying pipes on two-parameter foundations
           with generalized boundary condition by means of Green’s functions
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): M. Li, X. Zhao, X. Li, X.P. Chang, Y.H. Li This paper mainly concentrates on obtaining the explicit solutions of the forced vibrations of oil-conveying pipes on two-parameter foundations and studying the stabilities of these pipes. With the assistance of the Euler-Bernoulli assumption, the dynamic equations of the pipes are modelled by means of Hamilton’s principle. The generalized boundary condition (BC), which can be reduced to many different simple BCs, is considered in the vibration problems. Green’s function and the superposition property of linear vibrations are employed to derive the analytical solutions, and the Laplace transforms are applied with intention of gaining the Green’s functions under various BCs. In the numerical section, the present solutions are validated by comparing with the results in the other literature. In addition, the effects of some important physical parameters, for instance boundary stiffness, foundation parameters, geometric parameters, etc., on the natural frequencies and the critical flow velocities are discussed as well.
       
  • Co-rotational 3D beam element for nonlinear dynamic analysis of risers
           manufactured with functionally graded materials (FGMs)
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): J.C.R. Albino, C.A. Almeida, I.F.M. Menezes, G.H. Paulino This paper considers a co-rotational beam formulation for beams, which is used for the finite element analysis of flexible risers and pipelines made of functionally graded materials. The influence of material gradation is addressed using an exponential variation of properties throughout the thickness of the pipe. Space discretization of the equilibrium equations is derived based on the Euler–Bernoulli assumptions considering two-node Hermitian beam elements which are referred to a co-rotation coordinate system attached to the element local frame of coordinates. The geometric non-linear effects of the beam are considered under large displacement and rotations, but under small-strain conditions. The deflections of the riser result from forces caused by self-weight, buoyancy, sea currents, waves, the action of floaters, seabed-structure interactions, and ship’s motion. We provide numerical examples and compare our results with the ones available in the literature. In addition, applications related to practical offshore engineering situations are considered to highlight the behavior of functionally graded materials (FGMs) as compared to homogeneous risers.
       
  • Analytical solution of three-dimensional two-layer composite beam with
           interlayer slips
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): B. Čas, I. Planinc, S. Schnabl This paper focuses on development of a new mathematical model and its analytical solution for the analysis of the mechanical behavior of geometrically and materially linear three-dimensional (3D) two-layer composite beams with interlayer slips between the layers. Consequently, the analytical solution of the mechanical behavior of elastic 3D two-layer composite beams with interlayer slips is derived for the first time. In the illustrative example, the cantilever 3D two-layer timber-concrete composite beam with interlayer slips is analysed, and the analytical results for various kinematic and equilibrium quantities are given. Besides, it is demonstrated that in case of the shear-stiff 3D two-layer composite beams with interlayer slips, the deformations in transverse XZ and lateral XY planes are mutually independent. The results obtained can be used as a benchmark solution.
       
  • Performance and sensitivity analysis of UHPFRC-strengthened bridge columns
           subjected to vehicle collisions
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Wei Fan, Xin Xu, Zhiyong Zhang, Xudong Shao Bridge columns made of normal concrete are evidenced to be susceptible to vehicle collisions. Particularly in the United States, vehicle collision has become one of the primary causes of bridge failures. This is largely due to the low crashworthiness of a conventional reinforced concrete (RC) column. Ultra-high-performance fiber-reinforced concrete (UHPFRC) as one of advanced concrete materials has been experimentally demonstrated to possess excellent strength, durability, impact resistance and energy-absorbing capacity. Accordingly, one type of UHPFRC-strengthened columns was proposed in this study as an alternative to RC columns that may be at risk for vehicle collision incidents. High-resolution finite element (FE) models were developed to investigate the performance of UHPFRC-strengthened columns subjected to vehicle collisions. In the high-resolution FE model, a three-span simply-supported girder bridge (including girder, pier column, column cap, bearing, etc.) was adopted and modelled. Material models regarding normal concrete and UHPFRC as well as the vehicle model were carefully calibrated by experimental data. The influence of initial gravity loads on impact responses was found to be pronounced, and a damping-based method was proposed to efficiently exert permanent loads on pier columns prior to a collision. Three different simplified models, as published in current studies, were investigated to replace the whole bridge model. Two single-column models with different boundaries were shown to have low accuracy. The pier-bent model considering the superstructure gravity was demonstrated as capable of predicting collision-induced responses that are in good agreement with the high-resolution FE model. The impact resistances of both RC and UHPFRC-strengthened columns were extensively investigated using the appropriate simplified model. The crashworthiness of UHPFRC-strengthened column was found to be considerably superior to that of RC column. An extensive parametric study was performed using response surface methodology to explore the influences of reinforcement ratios, thickness of UHPFRC jacket, UHPFRC strength and initial impact speed. The impact-resistant performance is mostly sensitive to changes in the thickness of UHPFRC jacket when the impact speed is not very high. On the contrary, the residual capacity of the bridge column is hardly increased by thickening UHPFRC jacket. In addition, the developed response surface models provided easy estimation of impact-induced responses of an UHPFRC-strengthened column, which have potential use as the surrogates of time-consuming FE simulations to efficiently examine the reliability and optimization of bridge columns under impact loadings.
       
  • Out-of-plane flexure behaviour of fly ash-lime-gypsum brick masonry walls
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): K. Gourav, B.V. Venkatarama Reddy Industrial by-products such as fly ash is being used for the manufacture of building products such as fly ash bricks. This paper is focused on understanding the out of plane flexural behaviour of fly ash-lime-gypsum (FaL-G) brick masonry, through experimental investigations. Results of the flexure strength of FaL-G brick masonry walls (under different pre-compression) in the two orthogonal directions, are discussed. Load displacement and moment-curvature relationships for the two cases presented. The cracking flexural stress using linear elastic analysis was predicted and compared with the experimental value. The results reveal that (a) the flexure strength of FaL-G brick masonry walls increases linearly with the increase in pre-compression, (b) the flexure strength parallel to bed joints is two times more than that of the flexure strength perpendicular to bed joints under zero pre-compression, (c) lateral displacements for the FaL-G brick masonry walls are larger for the case of bending perpendicular to bed joints when compared with those for bending parallel to bed joints and (d) The cracking flexural stress for the FaL-G brick masonry can be predicted closely with those of experimental values using linear elastic analysis.
       
  • Analysis of nail properties for joint design
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Carmen Sandhaas, Rainer Görlacher Design of nailed joints requires properties such as yield moment, tensile strength, withdrawal or head pull‐through parameters. These properties are either given as empirical equations in codes or, especially for profiled nails, in technical documents for the individual nails. This is not only cumbersome; it also requires considerable testing effort from nail producers. Based on an extensive database comprising more than 9000 test results carried out for certification purposes, analyses were carried out in order to develop more reliable input parameters for the design of nailed joints. It could be shown that the yield moment can be correctly calculated using nail tensile test results. The withdrawal and head pull‐through parameters need to be experimentally determined also in future. The introduction of technical classes to which the individual nails are assigned, containing different numerical values for the input parameters, would facilitate the work of practitioners considerably as the need to consult a large number of technical documentation would not be necessary anymore.
       
  • Numerical investigations into the behavior of light rail bridges
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Yongcheng Ji, Yail J. Kim This paper presents various technical aspects related to bridges under light rail gravity loadings, including flexural and shear responses, deflection, serviceability, and dynamic load allowance. Unlike highway and conventional rail bridges, the behavior of light rail bridges has scarcely been reported; thus, limited information is available. Five types of benchmark bridges are designed with steel plate girders, prestressed concrete boxes, reinforced concrete T-girders, prestressed concrete I-girders, and closed steel box girders. Three-dimensional finite element models are developed to predict the behavior of these bridges when loaded by four representative light rail trains operated in the United States (Colorado, Massachusetts, Minnesota, and Utah), which results in 4,932 cases. Parameters for investigations involve structural configurations (simply-supported and continuous spans), geometries (girder spacing, span length, curvature, and skew), and loading characteristics (one-track-loaded and two-track-loaded with one to four articulated trains). A comparative study is conducted to evaluate the applicability of existing design specifications (highway and heavy-haul train loadings) that are frequently referenced in light rail bridge design. The flexural moment of the bridges is controlled by span length, the number of loaded tracks, and the axle spacing of the articulated trains. Contrary to the implications of horizontal curvature, those of skew angles are significant in altering the responses of the bridges concerning moments and fundamental frequencies. The deflection criteria of the existing specifications are not applicable to the light rail bridges; consequently, an alternative approach is suggested. Regarding dynamic load allowance, the predicted values are generally lower than those used in practice.
       
  • Flexural behavior of RC beams strengthened with NSM GFRP strips after
           exposed to high temperatures
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Gia Toai Truong, Hye-Hak Lee, Kyoung-Kyu Choi The present study investigated the flexural behavior after exposure to high temperature of reinforced concrete beams strengthened with glass fiber reinforced polymer (GFRP) strips. To strengthen the beams, the near surface mounted (NSM) method was used to install the GFRP strips inside concrete substrate. Two different adhesive materials of epoxy and mortar were used to bond the GFRP strips inside the concrete substrate. Two strengthened specimens using the mortar and epoxy, respectively, as adhesive materials were first exposed to fire, and then flexural test was performed. The test results showed that after exposure to high temperature, the GFRP strips using epoxy technique could be beneficial to retaining the flexural strength of the concrete beams. In contrast, after exposure to high temperature, the GFRP strips using mortar technique was beneficial to deformability, rather than flexural strength. Finally, analytical study was performed to predict the failure mode, strength, and deformation of the concrete beams after experiencing high temperature, and the analysis results showed good agreement with the test results.
       
  • A distributed parameter model for the piezoelectric stack harvester
           subjected to general periodic and random excitations
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Feng Qian, Tian-Bing Xu, Lei zuo Vibration-based energy harvesting using piezoelectric stacks has received increasing attention in recent years for its higher mechanical-to-electrical energy conversion capability in the d33 mode. However, most research on this type of harvesters is based on either the simplified one-degree-of-freedom model or transfer matrix model. This paper presents a distributed-parameter model for the multilayer piezoelectric stack transducer based on the axial vibration theory of a continuous bar. The presented analytical model is free from the assumption that the generated current is identically distributed over all the piezoelectric layers, which has been widely used by the existing models in literature. A first-order numerical model is also introduced to validate the performance of the analytical model on the prediction of voltage, current and power outputs of the harvester under different types of external excitations. Both the analytical and numerical models are firstly validated by experiments and then are used to predict the electrical responses of the stack harvester under general periodic and random excitations with different intensities. Experiment and simulation results demonstrate that the proposed distributed-parameter model has a good accuracy and reliable performance in the prediction of the electrical responses.
       
  • Experimental and numerical investigation of the collapse of pointed
           masonry arches under quasi-static horizontal loading
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Giulia Misseri, Matthew Justin DeJong, Luisa Rovero Pointed arches can exhibit a relevantly different behaviour from circular arches when subjected to horizontal actions. This paper considers the response of 11 reduced scale, dry-block pointed arches with varying geometry subjected to tilt tests. Crossed comparison between experimental and numerical results with variations in sharpness and thickness of models highlighted the sliding-governed response of a subset of samples. Thus, a novel, simplified, two-bar model, which assumes free sliding at the keystone interface and tackles the behaviour recorded during tests, is proposed. Moreover, the values of load multipliers obtained using limit analysis are compared to results from DEM modelling of the tilt tests. Finally, the sensitivity of the lateral response to the friction coefficient is carried out through DEM to define the sliding - hinging domain for possible geometric variations of pointed arches.
       
  • Experimental and numerical studies of ultra-high performance concrete
           targets against high-velocity projectile impacts
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Jian Liu, Chengqing Wu, Yu Su, Jun Li, Ruizhe Shao, Gang Chen, Zhongxian Liu Ultra-high performance concrete (UHPC) which is known for high strength, high toughness, excellent ductility and good energy absorption capacity can be adopted as an ideal material in the impact resistant design of structures. In the present study, impact responses of UHPC targets with 3 vol-% ultra-high molecular weight polyethylene (UHMWPE) fibres and UHPC targets with 3 vol-% steel fibres are experimentally investigated subjected to high-velocity projectile penetration, and plain concrete targets under the same loading scenarios are also tested as control specimens for comparative purpose. In addition, numerical studies are conducted to simulate the projectile penetration process into UHPC targets with the assistance of a computer program LS-DYNA. The numerical results in terms of the depth of penetration (DOP) and crater diameter as well as projectile abrasions and damages are compared with the experimental results. Moreover, DOPs of these two types of UHPC targets obtained from tests are compared with the previously proposed empirical model.
       
  • An integrated risk assessment of onshore gas transmission pipelines based
           on defect population
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Maciej Witek, Anatolii Batura, Igor Orynyak, Mykhailo BorodiiGraphical abstractGraphical abstract for this article
       
  • Research and practice on progressive collapse and robustness of building
           structures in the 21st century
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Jose M. Adam, Fulvio Parisi, Juan Sagaseta, Xinzheng Lu Extreme events (i.e. terrorist attacks, vehicle impacts, explosions, etc.) often cause local damage to building structures and pose a serious threat when one or more vertical load-bearing components fail, leading to the progressive collapse of the entire structure or a large part of it. Since the beginning of the 21st century there has been growing interest in the risks associated with extreme events, especially after the attacks on the Alfred P. Murrah Federal Building in Oklahoma in 1995 and on the World Trade Center in New York in 2001. The accent is now on achieving resilient buildings that can remain operational after such an event, especially when they form part of critical infrastructures, are occupied by a large number of people, or are open to the public. This paper presents an ambitious review that describes all the main advances that have taken place since the beginning of the 21st century in the field of progressive collapse and robustness of buildings. Widely diverse aspects are dealt with, including: (1) a collection of conceptual definitions, (2) bibliometric details, (3) the present situation and evolution of codes and design recommendations, (4) quantification of robustness, (5) assessing the risk of progressive collapse, (6) experimental tests, (7) numerical modelling, and (8) research needs. Considering the comprehensive range of these aspects, this paper could be of great use to professionals and researchers who intend to enter the field of the progressive collapse of building structures and also to other experts who require an extensive and up-to-date view of this topic.Graphical abstractGraphical abstract for this article
       
  • Experimental study on the hysteretic behavior of ECC-encased CFST columns
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Jingming Cai, Jinlong Pan, Hao Su, Cong Lu Concrete-encased concrete-filled steel tube (concrete-encased CFST) columns, which is a conjunction of normal steel reinforced concrete (RC) and CFST columns, have been widely used in structural engineering. However, the outer RC component tends to crush in the early stage due to the significantly different mechanical performance of outer concrete and inner CFST. In this paper, it is proposed to substitute outer concrete with engineered cementitious composite (ECC) to form ECC-encased CFST columns. This paper presents an experimental study on the hysteretic behavior of ECC-encased CFST columns. Eleven specimens, including seven ECC-encased CFST columns and four concrete-encased CFST columns were tested under cyclic loading. According to the test results, ECC-encased CFST columns exhibited stable ductile behavior and the cumulative energy dissipation is about twice as much as that of concrete-encased CFST columns with same geometry. Also, the increase of steel tube diameter and stirrup ratio have positive effects on the hysteretic behavior of ECC- encased CFST columns.
       
  • Analysis on nonlinear vibrations near internal resonances of a composite
           laminated piezoelectric rectangular plate
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Y.F. Zhang, W. Zhang, Z.G. Yao The nonlinear vibrations and chaotic motions of a simply supported symmetric cross-ply composite laminated piezoelectric rectangular plate subjected to the transverse and in-plane excitations are analyzed in the case of primary parametric resonance and 1:3 internal resonance. It is assumed that different layers of the symmetric cross-ply composite laminated piezoelectric rectangular plate are perfectly bonded to each other and with piezoelectric actuator layers embedded in the plate. Based on the Reddy’s third-order shear deformation plate theory, the nonlinear governing equation of motion for the composite laminated piezoelectric rectangular plate is derived by using the Hamilton’s principle. The Galerkin’s approach is employed to discretize the partial differential governing equation to a two-degree-of-freedom nonlinear system under combined the parametric and external excitations. The method of multiple scales is utilized to obtain the four-dimensional averaged equation. Numerical method is used to find the bifurcation diagram, the periodic and chaotic motions of the composite laminated piezoelectric rectangular plate. The numerical results illustrate the existence of the periodic and chaotic motions in the averaged equation. It is found that the chaotic responses are especially sensitive to the forcing and the parametric excitations. The influences of the transverse, in-plane and piezoelectric excitations on the bifurcations and chaotic behaviors of the composite laminated piezoelectric rectangular plate are investigated numerically.
       
  • Deck-pier connection detail for the simple for dead load and continuous
           for live load bridge system in seismic regions
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Ramin Taghinezhadbilondy, Aaron Yakel, Atorod Azizinamini The steel bridge system referred to as Simple for Dead Load and Continuous for Live Load (SDCL) has gained popularity in non-seismic regions of the United States of America. The system provides enhanced service life and lower inspection and maintenance costs as compared to conventional steel systems. To-date, no research studies have been carried out to evaluate the behavior of the SDCL steel bridge system in high seismic regions. The SDCL concept for seismic regions requires a suitable connection between the girder and pier. The research presented in this paper investigates an integral pier SDCL steel bridge system. The structural behavior and force resistance mechanism of a proposed seismic detail was evaluated through an analytical study. An equation was developed to predict the ultimate connection capacity under seismic loading. This paper presents the results of Phase I of an ongoing, three-phase effort, that will culminate in the development of a set of details and associated design provisions to develop a version of the SDCL steel bridge system suitable for use in high seismic regions.
       
  • Vibration control of vortex-induced vibrations of a bridge deck by a
           single-side pounding tuned mass damper
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Wenxi Wang, Xiuyong Wang, Xugang Hua, Gangbing Song, Zhengqing Chen This paper proposes a new method to mitigate vortex-induced vibrations (VIVs) of a bridge deck using a single-side pounding tuned mass damper (SS-PTMD). The SS-PTMD is a passive control device and comprises an undamped tuned mass with a pounding boundary covered with viscoelastic (VE) materials layer. A nonlinear force model for describing impact behavior of VE materials is used to simulate the response of a single degree of freedom (SDOF) system controlled by a SS-PTMD. The free pounding experiments are performed to determine the model parameters of impact force and validate the simulation method. The optimal design of SS-PTMD for SDOF system subjected to sinusoidal excitation is carried out by numerical optimization, and the optimized SS-PTMD is applied to control the vertical VIVs of a bridge deck. The control performance is experimentally examined by elastically mounted section model tests in wind tunnel. In addition, the classical wake oscillator model is used to predict the behavior of the coupled fluid-structure system under VIV and explore the control performance of the SS-PTMD. The experimental results show that the maximum response of the bridge deck model was reduced by 94% when a SS-PTMD with mass ratio of 2% was applied. It is also shown that nonlinearity in vortex shedding forces has little influence on control performance of SS-PTMD optimized under sinusoidal excitation.
       
  • A new nonlinearly tapered FGM piezoelectric energy harvester
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Alireza Keshmiri, Nan Wu, Quan Wang This work presents an analytical model for the development of a piezoelectric energy harvester with general nonlinear geometry and functionally graded material (FGM) properties based on Adomian decomposition method. The model is applied to geometrically and materially non-uniform beams with structural strain rate damping and surface bonded piezoelectric layers to derive the dynamic response of the smart structure to base motion excitations and efficiently harvesting the subsequent vibrational energy. Firstly, the steady state vibration response of the smart non-uniform FGM beam subjected to a harmonic base motion is obtained and then electromechanical outputs of the piezoelectric patches are analytically derived. Furthermore, a comprehensive parametric study for bimorph piezoelectric energy harvesters with different nonlinearly tapered geometry and FGM properties in a wide frequency range has been done. Considering the same volume of the harvester, it is demonstrated that the novel non-uniform FGM design can significantly increase the electrical output of the harvester by more than 19.76 times compared to the traditional uniform homogenous design. With the presented methodology, optimum structural design for piezoelectric energy harvesters with respect to the operation frequency domain can be effectively achieved.
       
  • Finite element analysis on the seismic behavior of fully prefabricated
           steel frames
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Hao Yin, Gang Shi This paper presents a method of finite element (FE) modeling and analysis of the seismic behavior of fully prefabricated steel frames with end-plate joints, flexible braces and composite slabs. The main idea and objectives of this paper is to develop a finite element model with high accuracy, good stabilization and acceptable computational costs for the simulation of the cyclic behavior of multi-story steel frames with bolted end-plate joints and concrete slabs. Because of the apparent tension-compression asymmetry of flexible braces, and the complex connection details between slabs and steel structures, as well as the huge number of contact interactions between interfaces, the cyclic behavior of this type of frame cannot be simulated accurately with commonly used line-element models, shell element models, or multi-scale models. A quasi-static test of a full-scale three-story fully prefabricated steel frame under cyclic horizontal loads by the present authors was simulated with the finite element model. Hollow section box columns, I-section beams, end-plates, inner diaphragms and stiffeners were modeled using shell elements; high strength bolts and concrete slab were modeled with solid elements; and flexible braces and rebar were modeled with truss elements. In order to develop a mesh skill to reduce computational costs while ensuring calculation accuracy, several FEM models were built and validated against previous experimental studies: static testing of bolted T-stub connections and bolted tension splices, static and cyclic testing of bolted end-plate steel joints, push-out tests of stud shear connectors, as well as static and cyclic testing of bolted end-plate composite joints. To simulate the “elastic-yield-hardening in tension, and buckling-without capacity in compression” behavior of the flexible braces, a simplified model in ABAQUS based on truss elements was developed and validated against previous tests. Results showed that the proposed FE modeling method could accurately simulate the static and cyclic performance of bolted T-stub connections, bolted tension splices, bolted end-plate steel joints, stud shear connectors, bolted end-plate composite joints and flexibly braced steel frames. Deformation capacity, cyclic behavior, horizontal loading performance, energy dissipation and stiffness degradation of steel frames with bolted end-plate joints, prefabricated slabs and flexible braces could be accurately simulated by this FEM model, providing a practical and accurate modeling method for similar structures. In addition, further research on the structural seismic performance simulation, parametric study and seismic design method could be carried out using the finite element model developed in this paper.
       
  • Assessment of the efficiency of traditional earthquake resistant
           techniques for vernacular architecture
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Javier Ortega, Graça Vasconcelos, Hugo Rodrigues, Mariana Correia Specific architectural elements can be identified in constructions located in regions frequently exposed to earthquakes. These earthquake resistant features were developed empirically by local communities to protect their built-up environment. Research in these traditional practices, resulting from a local seismic culture, is a relevant and positive approach, since it focuses on the strength of the system rather than on its weaknesses. Its integration into current vernacular building practices can help to preserve and retrofit surviving in-use examples while respecting their authenticity. The main goal of the present work is to assess numerically the efficiency of traditional earthquake resistant solutions to mitigate the seismic vulnerability of vernacular architecture. The paper thus presents the results of a detailed numerical study based on finite element modeling and nonlinear static (pushover) analysis intended to quantitatively evaluate the influence of each technique on the seismic behavior of vernacular constructions and to better understand their structural role under seismic loading.
       
  • Experimental study on the behavior of precast segmental column with domed
           shear key and unbonded Post-Tensioning tendon under impact loading
    • Abstract: Publication date: 15 October 2018Source: Engineering Structures, Volume 173Author(s): Xihong Zhang, Hong Hao, Chao Li, Tin Van Do Precast segmental columns have been more and more popularly used in constructions of prefabricated reinforced concrete (RC) structures in recent years. During its servicing life the precast segmental column might be subjected to lateral impact loads from hazards such as falling rock and vehicle collision etc., which however has not been well understood. It is therefore necessary to properly understand the response and vulnerability of segmental column under impact loading. A previous experimental study revealed that the trapezoidal prism shear key on concrete segment could effectively reduce lateral slippage between segments under lateral impact loading, but stress concentration near the shear key led to crushing damage to concrete segment. A new shear key design, i.e., domed shear key with smoothed curvature is proposed in this study. Precast segmental columns with domed shear key are fabricated and tested. This paper presents the test results of scaled segmental columns with this new shear key design. The performance of segmental column with the new dome shear key is compared with previously tested columns with trapezoidal shear key and plain segmental column without shear key. Furthermore, the segmental columns with the new domed shear keys were impacted at different locations along the column including the column mid-span, the segmental joint, and the bottom segment to examine the influences of different impact locations on their impact resistant capacities, and the response and failure modes.
       
  • Prestressed cold-formed steel beams: Concept and mechanical behaviour
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Nicolas Hadjipantelis, Leroy Gardner, M. Ahmer Wadee An innovative concept, whereby the load-carrying capacity and serviceability performance of cold-formed steel beams are enhanced by utilising prestressing techniques, is presented. The prestressing force is applied by means of a high-strength steel cable, which is housed at a location eccentric to the strong geometric axis within the bottom hollow flange of the cold-formed steel beam, inducing initial stresses in the beam that are opposite in sign to those introduced during the subsequent loading stage. As a consequence, the development of local instabilities during loading is delayed and thus the capacity of the beam is enhanced. Furthermore, the pre-camber induced during prestressing, as well as the contribution of the cable to the bending stiffness of the system, decrease the overall vertical deflections of the beam. The conceptual development of prestressed cold-formed steel beams and a study investigating the potential benefits are presented. The mechanical behaviour of the proposed beams in both the prestressing and imposed loading stages is described in terms of analytical expressions, while failure criteria for the design of the cold-formed steel beam and the cable are also developed by employing interaction equations in conjunction with the Direct Strength Method. Geometrically and materially nonlinear finite element analysis with imperfections is employed to simulate the behaviour of the proposed beams. Sample numerical results are presented and compared with the developed analytical expressions and failure criteria, demonstrating the substantial enhancement in moment capacity and serviceability performance offered by these beams.
       
  • A parametric study on the final blade installation process for monopile
           wind turbines under rough environmental conditions
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Zhiyu Jiang, Zhen Gao, Zhengru Ren, Ye Li, Lei Duan Single blade installation is a method for installing wind turbine blades. If a jack-up vessel is used during an o shore installation, the wind turbine blade is mainly subjected to wind loads and experiences resonant motions, and the monopile is subjected to wave-induced vibrations. The blade mating process can be challenging if large relative motions occur between the blade root and the monopile top. This study numerically models a blade installation system that consists of a pre-installed monopile and nacelle assembly, and a 5 MW blade with tugger lines. By analyzing the blade-root and the hub motion radii from time-domain simulations, we evaluate the effects of mean wind speed, wind turbulence, significant wave height, wave spectrum peak period, wind-wave misalignment, and water depth on the blade installation. For the alignment phase, the blade-root motion is critical, especially when the mean wind speed and turbulence are high. The hub motion can be important when the monopile resonant responses are prominent. The relative in-plane motions rather than the hub or the blade motion alone should be considered during the assessment. For the mating phase, the high-frequency components of the responses are important in general. Because of the dominant flange-hole motions at the monopile top, an increase in water depth reduces the success rate of mating.
       
  • A vibration prediction model for culvert-type railroad underpasses
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Manuel F. Báez H., Alberto Fraile, Javier Fernández, Lutz Hermanns Although underpasses are low-cost solutions widely used in high-speed railway lines, their dynamic analysis is complex given the large number of variables involved in the problem and the high computational cost of detailed 3D models.The objective of this study is therefore to present a simple and fast 3D method for estimating the dynamic behavior of culvert-type underpasses subjected to dynamic loads induced by high speed trains under normal operating conditions. This model was adjusted to data gathered in situ during a measurement campaign on the high-speed line between Segovia and Valladolid in Spain.The prediction method is based on a sub-structuring approach with three key ingredients: an emission 2D finite element model that simulates the track; a slab model based on Kirchhoff theory and the Rayleigh-Ritz method using trigonometric shape functions; and sidewall-models using a formulation of a finite-length beam on a viscoelastic foundation. The emission model estimates the contact forces for the slab using the vertical dynamic behavior of the railway track, and the slab model accounts for the contribution of the soil-structure interaction that takes place at the sidewalls by means of the frequency-dependent stiffness at the corresponding joints.
       
  • An axiomatic/asymptotic evaluation of the best theories for free vibration
           of laminated and sandwich shells using non-polynomial functions
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): J.C. Monge, J.L. Mantari, S. Charca, N. Vladimir This paper presents Best Theory Diagrams (BTDs) constructed from non-polynomial terms to identify best shell theories for the free vibration analysis of laminated and sandwich shell. The shell theories have been constructed using Axiomatic/Asymptotic Method (AAM). The refined models are implemented following the compactness of a unified formulation developed. The governing equations are derived from the Hamilton’s Principle. Navier-Type solution technique is used for solving the eigenvalue problem of simply supported shell. The BTDs use 3D equilibrium solutions as a reference. The BTDs built from non-polynomial functions are compared with Maclaurin expansions. The results are compared with Layerwise solutions. Cylindrical and spherical shells with different layer-configurations are investigated. The results demonstrate that the shell models obtained from the BTD using non-polynomial terms can improve the accuracy obtained from Maclaurin expansion for a given order of expansion of a displacement field.
       
  • Experimental study of the mechanical behavior of timber-concrete shear
           connections with threaded reinforcing bars
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Decroly Denouwe Djoubissie, Adamah Messan, Eric Fournely, Abdelhamid Bouchaïr This paper presents the experimental results of push-out tests on simple timber-concrete connection systems. The tested configurations concern the notch without rod, the rod without notch and the notch combined to rod. The rod is composed by common reinforcing steel bar threaded at their extremity and screwed in the timber beam. These fasteners are combined with rectangular or triangular notch connections between timber and concrete. These solutions are chosen because they are simple to apply in a timber-concrete composite structure using materials available in the local market. The mechanical properties such as the strength, the slip modulus and the failure mode of the tested specimens are obtained from the load-slip curves of the push-out tests. The comparisons are done to evaluate the differences and similarities between the various tested shear connections. The comparisons show the efficiency of the simple composite systems of connections tested using the reinforcing steel bars alone or combined with a notch connection in the timber beam.
       
  • Experimental and numerical analyses of flexurally-strengthened concrete
           T-beams with stainless steel
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Noel Franco, Hugo Biscaia, Carlos Chastre This work presents the results and the main conclusions of a series of experimental tests carried out to evaluate the efficiency of post-installed stainless steel reinforcement on the flexural strengthening of Reinforced Concrete (RC) T-beams when the bonding techniques EBR (Externally Bonded Reinforcement), NSM (Near Surface Mounted) and MA-EBR (EBR with Mechanical Anchors) are used. The RC T-beams were also modelled using a commercial Finite Element (FE) software in order to predict their behaviour until the rupture. For this purpose, a set of single-lap shear tests were also carried out to evaluate the local bond-slip relationships developed within the Stainless Steel (SS)-to-concrete interface. Due to the experimental bond-slip relationships, the numerical simulations were able to predict, with good accuracy, the different behaviours of the RC T-beams until their rupture. Moreover, the different rupture modes observed on all the RC T-beams herein tested were very well estimated by the numerical analyses. The tests of the RC T-beams showed that all the strengthening techniques allowed their flexural stiffness to be increased. Nevertheless, the RC T–beams strengthened with the EBR and NSM techniques had premature ruptures, i.e. the rupture in the RC T-beams occurred even before the yielding of their steel reinforcements. The RC T-beam strengthened with the MA-EBR technique showed good ductility and the highest load bearing capacity, which means that the MA-EBR technique is the best bonding technique herein used.Graphical abstractGraphical abstract for this article
       
  • Analysis of restrained composite beams exposed to fire using a hybrid
           simulation approach
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Mustesin Ali Khan, Liming Jiang, Katherine A. Cashell, Asif Usmani Obtaining an accurate simulation of the boundary conditions is very challenging but it is essential in order to represent the true behaviour of the whole structure in fire. In recent years, hybrid simulation has been emerging as an efficient and economical method for simulating realistic boundary conditions in the field of earthquake engineering. This technique can be used to study the load redistribution that may occur in a structural system as a result of locally elevated temperatures. In this paper, the fire-exposed element will be modelled in one analysis (a 3D model) and the rest of the structure in another analysis (a 2D model). This kind of sub-structuring enables the behaviour of the structural system as a whole to be studied. A hybrid simulation (HS) approach is presented and successfully implemented using the OpenFresco and OpenSees software. This approach enables the simulation of the correct restraint provided by the cold structure to the fire affected structural element. The HS analysis of a composite beam is compared with an unrestrained or simply supported version to highlight the difference in behaviour. Finally, the Cardington restrained beam test is modelled to demonstrate the potential of HS technique. Good agreement with the test results highlights that HS approach can be an effective method for studying the behaviour of the whole structural system.
       
  • Multiple internal resonances and modal interaction processes of a
           cable-stayed bridge physical model subjected to an invariant
           single-excitation
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Ceshi Sun, Yaobing Zhao, Jian Peng, Houjun Kang, Yueyu Zhao There exist complex internal resonances in cable-stayed bridges. In order to study multiple internal resonances under the excitation of an invariant single-excitation and to ascertain the modal interaction processes, a nonlinear dynamic experiment of cable-stayed bridge was carried out. The modal parameters of the experimental physical model were evaluated by two finite element models (the OECS and MECS). Mode shapes were classified and compared to distinguish the in-plane and out-of-plane as well as the global, local and hybrid modes. Potential internal resonances were recognized by investigate the ratios between cable frequencies and the OECS frequencies. Then, attention was paid not only to the steady-state responses but also the coupling processes. It was observed that multiple internal resonances could induce large amplitude vibrations of the entire bridge, including the “beat vibration” of long-cables. Moreover, the sum of the two beat frequencies was equal to the excitation frequency. These phenomena were also found in transient analysis by the MECS finite element model. The interaction processes of the multi-mode resonances were revealed by separating vibration signals using the zero-phase-shift filtering technology and by precisely linking the observed modes to the MECS modes with frequency relations. Research shows that: the forced vibration, 2:1 local-local internal resonance and combined internal resonance had occurred simultaneously in the physical model.
       
  • Shear strengthening of RC deep beams with cement-based composites
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Rizwan Azam, Khaled Soudki, Jeffrey S. West, Martin Noël The effectiveness of cement-based composite systems for strengthening reinforced concrete (RC) deep beams was compared to an epoxy-based carbon fiber reinforced polymer (CFRP) system. Two types of cement-based systems were investigated: carbon fabric reinforced cementitious mortar (CFRCM) and carbon fiber reinforced polymer (CFRP) grid embedded in mortar. Experimental results revealed that the cement-based strengthening systems performed better compared to the epoxy-based system in terms of the observed increase in shear capacity relative to the ultimate strengths of the strengthening system. This is possibly due to the bi-directional fabric used in the cement-based strengthening systems compared to the unidirectional sheets used in the epoxy-based strengthening system as well as their improved bond to the concrete substrate; the beams strengthened with CFRP sheets failed by debonding of the CFRP sheet, whereas no debonding was observed in beams strengthened with cement-based systems. The failure loads of tested beams were predicted using a simple strut and tie model by incorporating the effect of the strengthening system in the diagonal strut capacity.
       
  • Optimization of cable pre-tension forces in long-span cable-stayed bridges
           considering the counterweight
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Chaolin Song, Rucheng Xiao, Bin Sun Over the past 20 years, many long-span cable-stayed bridges with asymmetric spans have been constructed, and the counterweight is always used to balance the self-weight of the main span. This paper presents an optimization method to determine the cable pre-tension forces in long-span cable-stayed bridges considering the counterweight. This method includes: finite element (FE) model, formulation of the optimization problem and optimization algorithm. FE model is established considering the geometrical nonlinearity. The optimization problem is formulated with the objective of minimum weighted total bending energy. In addition, the constraints for the cable pre-tension forces, the bending moment of the girder and the tower, the load of the counterweight, the bearing reactions of the transition piers and auxiliary piers are all implemented in the optimization model. The optimization algorithm solves the optimization problem through the variable-step search along each design variable including the cable pre-tension forces, the load and the range of the counterweight. The efficiency and the accuracy of the proposed method are demonstrated by an application example and the results exhibit the importance of considering counterweight in the design of asymmetric cable-stayed bridges.
       
  • Comparison of experimental research and nonlinear advanced FEM analysis of
           load capacity and deformability of slender HSC columns in bi-axial bending
           
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Krzysztof Koziński, Andrzej Winnicki The paper compares results of own experimental research of sixteen reinforced concrete columns made of HSC in bi-axial bending with advanced three-dimensional FEM analysis. Computational analysis with application of TNO DIANA v.9.4 system and pre and post processor MIDAS FX+ was conducted. The analysis was used mostly to check a compatibility of the conducted research with the advanced 3D numerical model and to prove a usefulness of applied numerical model in calculation of load-bearing capacity of bi-axially bending columns. Mechanical properties of concrete and reinforcing steel were assumed based on the results of material tests.
       
  • Experimental and numerical analyses of variability in the responses of
           imperfect slender free rigid blocks under random dynamic excitations
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Charlie Mathey, Cyril Feau, David Clair, Laurent Baillet, Michel Fogli Due to the well-known sensitivity of the behaviors of free structures under seismic excitations, the question of the aptitude of a numerical model to accurately represent them arise. To contribute to the answer to this question, this article presents experiments which were carried out on the shaking table of CEA/Saclay in France, on three rigid blocks with geometrical defects, inevitably due to the manufacturing process, subjected to 100 realizations of a random process. These tests were analyzed using specifically-developed indicators, and compared with the results yielded by two numerical models, one with a symmetrical geometry and the other with a non-symmetrical geometry, calibrated to reproduce out-of-plane behavior identified through release tests. Counter-intuitively, this article shows that a numerical model can predict motion over a longer period than an experiment performed on a supposedly identical block. From a statistical point of view, despite experimental uncertainties this article shows a good agreement between numerical and experimental results. Finally, a numerical study, performed using artificial seismic signals, showed that the assumption of perfect geometry can lead to an underestimation of the risk of overturning. Moreover, it is showed that a symmetrical model with a realistic slenderness correction can provide an overestimation of this risk under 1D excitation, but not in 2D.
       
  • Experimental investigation on the CFRP strengthening efficiency of steel
           plates with inclined cracks under fatigue loading
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): N.J. Aljabar, X.L. Zhao, R. Al-Mahaidi, E. Ghafoori, M. Motavalli, Y.C. Koay Employing advanced material such as carbon‐fibre‐reinforced‐polymer (CFRP) in tension fatigue strengthening of aged roads and railway bridges have shown a great capability of arresting or delaying crack initiation and/or propagation in steel structures. However, it is not clear whether the fatigue behaviour and the CFRP strengthening efficiency is the same when the cracked-steel elements exhibit a state of complex loading. The aim of this paper is to investigate the fatigue behaviour of the CFRP strengthening of steel plates with central initial inclined cracks with a focus on the effect of the CFRP properties. The initial slit-like cracks were oriented to introduce a state of combined action of tension (mode-I) and shear (mode II) stresses at the crack tips. The key parameters in this study are the mixed‐mode (shear to tension stresses) ratio, the crack-starter length ratio (initial crack length to the plate width), patching configurations, and mechanical properties of the composite material. All the test specimens were artificially notched with central cracks of different damage levels. This study covered the fatigue performance of steel plates strengthened with two configurations of composite materials of different tensile stiffness (high modulus CFRP sheets, and normal modulus CFRP plates). Furthermore, the efficiency of strengthening systems of different fibre orientation relative to the initial crack angle was investigated. The outcomes of this study are extending the current knowledge of the CFRP strengthening to its applications on metal plates contain defects subjected to mixed-mode fatigue loading.
       
  • Mechanical properties of three-leaf masonry walls constructed with natural
           stones and mud mortar
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Nikiforos Meimaroglou, Harris Mouzakis Although earth is the first masonry mortar material with continuous use throughout history, little experimental research on stone masonry with mud mortars has been carried out, particularly concerning its restoration. This paper presents the experimental investigation of the mechanical properties of three-leaf masonry constructed with natural stones and clay (mud) mortars under compression focusing on the production and properties of the mortars. Two different mortar mixes were designed for the external and internal leaves. Soil was collected and prepared (crushing of clods, sieving, drying and mixing with river sand). The water content was defined by flow table tests. Evaluation of the raw materials used for the production of the mortars was done by examining the particle size distribution by hydrometer and by sieves and by measuring the concentration of the total soluble salts and the organic material, while the hardened mortar evaluation was done by measuring the compressive strength, the flexural strength and the volumetric shrinkage. The compressive strength, flexural strength and splitting tensile strength of stones were also determined. Wallettes were subjected to monotonic compression after a six-month maturation period to determine the compressive strength, modulus of elasticity and deformation characteristics of the masonry. Adequate compressive strength, low modulus of elasticity and high transverse and longitudinal deformations were documented.
       
  • Design rules for stainless steel welded I-columns based on experimental
           and numerical studies
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Shameem Ahmed, Safat Al-Deen, Mahmud Ashraf Stainless steel is characterised by its nonlinear stress-strain behaviour with significant strain hardening, although current design codes treat it as an elastic, perfectly plastic material like carbon steel. The continuous strength method (CSM) is a newly developed strain based design approach which was proposed for nonlinear metallic materials. With recent developments, CSM can be used to predict the cross-section resistance for stocky and slender sections, and CSM design rules have recently been proposed for predicting the buckling resistance of cold-formed RHS and SHS columns. Welded sections, however, could behave differently from cold-formed sections due to the presence of residual stresses. Despite offering more economic options in many design cases, research on stainless steel welded sections is very limited to date. In this study, the behaviour of stainless steel welded I-sections was investigated through a test program, and the investigation was complemented by finite element (FE) modelling. The test program covered tensile coupon tests, residual stress and initial geometric imperfection measurements, stub column tests and flexural buckling tests of pin-ended long columns. FE models were developed for both major and minor axis buckling based on test results, and the verified FE modelling technique was used to investigate the effects of cross-section slenderness λp, section height-to-width ratio H/Band the ratio of flange thickness-to-web thickness tf/tw on column curves of welded I-sections. Buckling formulas for welded I-columns were eventually proposed following the same philosophy recently adopted by the authors for cold-formed hollow section columns. The imperfection parameter was recalibrated appropriately to incorporate special features of welded I-sections. Two sets of equations were proposed to tackle the observed variation in buckling behaviour against major and minor axis buckling. Buckling resistance predictions obtained from the proposed method were deemed reliable showing good accuracy and consistency with test and FE results.
       
  • Behavior of columns of steel plate shear walls with beam-connected web
           plates
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Yigit Ozcelik, Patricia M. Clayton Steel plate shear walls with beam-connected web plates (B-SPSWs) are an alternative configuration of steel plate shear walls (SPSWs) where web plates are connected to the beams only. Detaching web plates from columns and introducing simple beam-column connections in B-SPSWs eliminate flexural demands in the columns resulting from web plate tension field action; consequently, the columns of B-SPSWs are designed primarily for axial loads. A recent study, however, showed that the columns of B-SPSWs resist significant flexural demands during earthquake shaking due to differential interstory drifts that result in significant column rotations at floor levels. Typical design methods (i.e., the Equivalent Lateral Force method and Modal Response Spectrum analysis) do not capture these rotations associated with differential drifts that might lead to column instability. A two-phase numerical study is conducted to evaluate the behavior and stability of B-SPSW columns. In the first phase, three-dimensional nonlinear response-history analyses are conducted to investigate the column stability for eighteen B-SPSWs with different geometric characteristics designed following two design approaches. The results suggest that column buckling is a possible mode of failure for one of the design approaches. In the second phase, a parametric study is undertaken to further investigate potential column buckling failure modes in B-SPSW columns and to establish an upper-bound estimate for the column buckling strength reduction due to column rotations at floor levels that are not considered in traditional design approaches.
       
  • Modal properties and seismic behaviour of buildings equipped with external
           dissipative pinned rocking braced frames
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): L. Gioiella, E. Tubaldi, F. Gara, L. Dezi, A. Dall'Asta This paper deals with the seismic protection of building frames by means of external dissipative systems. Dampers and external framing system can be arranged in several configurations, involving different kinematic behaviours and seismic performances. This study analyses a recently-developed solution called “dissipative tower”, which exploits the rocking motion of a steel braced frame, hinged at the foundation level, for activating the dampers. This system aims at controlling both the global response and the local storey deformation of the frame, by using a reduced number of viscous dampers. A state space formulation of the dynamic problem is presented in general terms, together with the solution of the seismic problem via the modal decomposition method.A parametric study is carried out to evaluate the influence of the added damping and of the braced frame stiffness on the modal properties and seismic response of a benchmark reinforced concrete frame retrofitted with the external dissipative towers. It is shown that the addition of the towers yields a regularization and reduction of the drift demand along the building height, but it may induce significant changes, not always beneficial, in the distribution of internal actions of the frame and in the absolute storey accelerations.
       
  • Experimental and numerical investigation of a hollow cylindrical water
           barrier against internal blast loading
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Wei Zhu, Guang-yan Huang, Chun-mei Liu, Shun-shan Feng A promising potential method of mitigating the blast effects caused by terrorist explosions is constructing a water barrier encircling an explosive found in public places. Eight in situ experiments were carried out to investigate the response and mitigation efficiency of hollow cylindrical water barriers against internal blast loading. Both the peak overpressure and the impulse along the side toward the base of the barrier were reduced mainly through reflection and diffraction of the blast wave. Numerical models corresponding to the experiments were developed using the commercial software AUTODYN and validated by the overpressure–time histories recorded in the experiments. The numerical results demonstrated that the water barrier enhanced the blast loading over the barrier, although it mitigated the blast loading along the side toward the base of the barrier. Parametric studies were carried out to comprehensively investigate the influences of the thickness, the height, and the inner diameter of the water barrier on the blast mitigation or blast enhancement effects. Adding a water cover on the top of the barrier was proved to be an effective way to eliminate the blast enhancement effects and efficiently improve the blast mitigation performance since it can substantially increase the kinetic energy extracted by the water barrier.
       
  • Assessment of load sharing behavior for micropiled rafts installed with
           inclined condition
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Dongho Kim, Garam Kim, Incheol Kim, Junhwan Lee As a combined foundation, micropiled rafts under compressive loads show the load-sharing behavior between raft and micropiles. The load carrying and sharing behaviors of micropiled rafts installed with inclined condition would become further complicated as a result of the coupled influences of group and inclined configurations. In this study, the 3D finite element analyses were performed to investigate the load carrying and sharing behaviors of inclined micropiled rafts. Changes in foundation configurations, including micropile inclination angle and spacing, were considered in the analyses. The load carrying capacity of micropiled rafts varied with the inclination angle of micropiles and the proportion of load carried by inclined micropiles was larger than for vertically installed condition. The values of the load sharing ratio αp for the inclined condition were obtained and analyzed. The normalized load-sharing model for inclined micropiled rafts was proposed with the modified load capacity interaction factor and design equations as a function of micropile configuration and inclination angle. Case studies were selected from the literature and adopted to compare with the calculated results using the proposed method. The calculated results were in reasonable agreement with measured load sharing ratios.
       
  • Non-linear 3D finite element analysis of the anchorage zones of
           pretensioned concrete girders and experimental verification
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Kizzy Van Meirvenne, Wouter De Corte, Veerle Boel, Luc Taerwe This paper focuses on the modelling of the anchorage zone of a pretensioned girder. The finite element software Abaqus was used to create a 3D non-linear finite element model (FEM). This analysis was performed on a full-scale pretensioned girder with end blocks and with various types of strand modelling, where accurate contact properties between prestressing steel and concrete are essential. The model has been validated by comparing the numerical strain results with the strain measurements on a full-scale girder with end blocks, which was produced in a precast concrete plant. At the same time, a parametric study was executed to determine the value of the coefficient of friction between the strands and the concrete and to examine the sensitivity of the input parameters of the model. The results have indicated that an accurate determination of the concrete properties at the time of release is very important. Furthermore, the Hoyer effect is analysed. It is found that the radial expansion of the strand in the finite element model is in good agreement with the theoretically calculated expansion of the strand which demonstrates the accuracy of the finite element model. In addition, it is shown that the Hoyer effect influences the force transfer of two adjacent strands. The aim of this research is to investigate the potential of an alternative FE model of a pretensioned girder based on strand to concrete frictional behaviour, rather than the commonly used models based on an assumed shear stress distribution along the transfer length.
       
  • Seismic behavior of 3-D ECC beam-column connections subjected to
           bidirectional bending and torsion
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Farshid Hosseini, Bora Gencturk, Hadi Aryan, Gustavo Cadaval Special moment resisting frames (SMF) are commonly used in low- and medium-rise buildings located in regions of high seismicity. Although adequate performance of this seismic force resisting system was observed in prior earthquakes in terms of protecting buildings from collapse, the formation of plastic hinges in the beams and columns causes irreparable damage to the beam-column connections. Recently, interest in using fiber-reinforced concrete (FRC) has been growing to enhance energy absorption capacity and damage tolerance of beam-column connections and other components in reinforced concrete (RC) buildings. Prior research has mostly focused on the application of steel FRC (SFRC) in 2-D beam-column connections. However, little is known about the performance of exterior beam-column connections that are usually subjected to more complex loading during an earthquake, involving bi-directional bending and torsion of the column. In addition to the loading, the geometry of the connection requires a more involved test setup (i.e., with an out-of-plane beam and proper boundary conditions). In this research, the use of engineered cementitious composites (ECC) in 3-D exterior beam-column connections is investigated experimentally to improve building seismic performance. ECC is a special class of high-performance fiber-reinforced cementitious composites (HPFRCC) that, compared to conventional concrete, exhibits higher tensile ductility, energy absorption and shear resistance, in addition to improved bond performance with reinforcing steel (rebar). To understand the performance of exterior beam-column connections under complex loading conditions, scaled 3-D specimens were constructed and tested under simulated seismic loads. To improve the performance of the connections, conventional RC was replaced with reinforced ECC (RECC) that extends from the panel zone to the adjoining beams and columns to cover the potential plastic hinge regions. This paper discusses the loading protocols, the test setup for 3-D exterior beam-column connections, and the improvement in the joint behavior with the application of RECC as compared to conventional RC. The results suggest that the efficient use of ECC in the potential plastic hinge regions can improve the capacity and damage tolerance of beam-column connections under realistic seismic loading conditions.
       
  • Impedance model for estimating train-induced building vibrations
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Chao Zou, James A. Moore, Masoud Sanayei, Yimin Wang In recent years, the exploitation of over-track construction in populated Chinese cities has resulted in buildings being subjected to potentially disturbing vibrations from rail lines in metro depots. Building owners and engineers are concerned about occupants’ complaints related to structure-borne noise and vibration related to human comfort. Similar concerns exist for laboratory buildings and manufacturing plants that use vibration-sensitive equipment.In Chinese metro depots, the subway trains usually run on the bottom floor of the metro depot and the vibrational energy they generate transmits through the primary building support structures, including columns and load-bearing walls, to the upper floors of the over-track buildings. In order to predict train-induced vibration levels in over-track buildings, a new impedance model is presented. The model accounts for the propagation of axial and bending waves through the columns and load-bearing walls from the foundation into the upper floors. The primary mode of transmission is through higher impedance axial waves across impedance discontinuities at the floors; while the transmission due to bending waves is attenuated more rapidly by the floors. The input for axial wave transmission is the measured vertical vibration levels at the base of the column at the foundation. The contributions from multiple columns/walls into a given floor have been found experimentally to be statistically independent so that the total response of a floor is obtained from a simple energy summation of contributions from all columns/walls where the inputs to each may vary depending, in part, on their distance from the train track.Measured train-induced vibrations at the foundation level and on upper floors in 14-story and 25-story buildings in Shenzhen metro depot were used to validate model predictions of vibration levels at upper floors relative to the foundation vibration. The support structures for both buildings include both columns and load bearing walls where the transmission involves both in-plane shear and dilatation at various angles within the wall though a conclusion from this study is that axial propagation in the vertical direction dominates. The impedance model predictions are in good agreement with the measured floor vibration levels.
       
  • Vertical ground reaction forces on rigid and vibrating surfaces for
           vibration serviceability assessment of structures
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Ehsan Ahmadi, Colin Caprani, Stana Živanović, Amin Heidarpour Lightweight structures are sensitive to dynamic force generated by human walking and consequently can exhibit excessive vibration responses. The imparted forces, known as ground reaction forces (GRFs), are a key input in the vibration serviceability assessment of footbridges. Most GRF measurements have been conducted on rigid surfaces such as instrumented treadmills and force plates mounted on strong floors. However, it is thought that the vibrating surface of a footbridge might affect the imparted human force. This paper introduces a unique laboratory experimental setup to investigate vertical GRFs on both rigid surface (strong floor) and a higher-frequency flexible surface (footbridge). 810 walking trials were performed by 18 test subjects walking at different pacing frequencies. For each trial, test subjects travelled a circuit of a vibrating footbridge surface followed by a rigid surface. A novel data collection setup was adopted to record the vertical component of GRFs, and the footbridge vibration response during each trial. Frequency-domain analysis of both single-step and continuous GRFs was then performed. The results show that the footbridge vibration affects GRFs, and changes GRF magnitudes for harmonics in resonance with the footbridge vibration (up to around 30% reduction in the dynamic load factor of the third harmonic). This finding, and the measured GRFs, can be used for more accurate vibration serviceability assessments of existing and new footbridges.
       
  • Seismic response control with inelastic tuned mass dampers
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Saman Bagheri, Vahid Rahmani-Dabbagh An elasto-plastic spring is utilized in a tuned mass damper (TMD) with eliminating its viscous damper to establish a new seismic response control system. A novel method to find the most appropriate parameters of the proposed elasto-plastic TMD (P-TMD) including its initial stiffness/frequency and yield strength is presented so as to reduce the seismic response of the main system with the P-TMD to a level of that obtained with a previously suggested optimum TMD. The parameters are used to compute the responses of several main structures in the form of single-degree of freedom systems with the proposed P-TMD under different earthquake excitations. To evaluate the effectiveness of the proposed device and tuning method, maximum displacements and accelerations are compared to those of optimum TMD systems as well as those obtained from uncontrolled ones. The numerical results show that the proposed device, when using the introduced procedure for selecting its design parameters, reduces the seismic responses significantly and can be used instead of the optimum TMD without the need for a viscous damper.
       
  • Quantitative assessment of resilience for earthen structures using coupled
           plasticity-damage model
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): M.H. Motamedi, A. Iranmanesh, R. Nazari In this work, structural resiliency is revisited as a composite term which consists of three interrelated capacities. A computational platform for quantitatively assessing the disaster-resilience of earthen structures is introduced with the use of a coupled plasticity-damage constitutive model. This numerical framework addresses the collapse resistance, damage sequences, strength residual state as well as resilience metrics. In particular, the plasticity model is furnished with combined isotropic-kinematic hardening internal variables accounting for the adaptive capacity of structural resilience. To simulate the transformative capacity at structural level, the model adopts the enhanced strain finite element method capturing the propagating fracture through the structural elements. Localized failure is detected by a bifurcation analysis. A cohesive based failure criterion is also incorporated to accurately represent the constitutive softening response in the case of progressive failure. Finally, we analyzed the factors that shape the structural resilience of earthen wall in the face of lateral loading. The performance of the structural system is examined for two conditions, namely fully intact structure and pre-damaged state.
       
  • Seismic performance of precast concrete column-to-column lap-splice
           connections
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): José F. Rave-Arango, Carlos A. Blandón, José I. Restrepo, Fabio Carmona Implementation of precast construction for buildings requires connection techniques that can speed up the process by requiring only simple and easy on-site activities, while still guaranteeing satisfactory strength, stiffness and ductility. The construction method should reduce the use of formwork and temporary bracing, avoid aesthetic problems and be compatible with the lifting capacity available, but at the same time avert an increase of costs that could threaten the viability of using precast concrete. In the case of columns, the use of single story segments connected above and below the beam-column joints is an alternative that reduces the element weight and overcomes several problems that may appear when the column segments are connected at mid-height between stories. This alternative, however, requires splicing the reinforcement at a location where rotational demands may induce inelastic behavior, which is deemed inadequate by procedures stated in several design codes, unless proven otherwise. In response to this, a beam-column joint, splicing the reinforcement at the column ends, is herein proposed and tested under cyclic loading to evaluate its behavior and the possibility of using this technique to build moment resisting frame structures in seismic regions. The results from the precast column-to-column connection were compared with those from a similar cast-in-place unit with no splices. Results show that the behavior of both units are comparable, with just slight differences in the cracking, damage distribution and hysteretic behavior, so that the use of the proposed precast column-to-column connection may be considered appropriate.
       
  • On estimation of seismic damage from ductility and hysteretic energy
           demands in equivalent oscillators using linear response
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Novonil Sen, Vinay K. Gupta Estimation of damage in a structure under anticipated seismic events is important for its performance-based design. This can be done in terms of the ductility and hysteretic energy demands for each of the anticipated plastic hinges under the anticipated ground motions. This study considers the possibility of quantifying the structural damage simply from the linear analysis based on the elastic design spectra of the ground motions and undamped mode shapes of the structure. A two-parameter model is first developed for the estimation of hysteretic energy demand in single-degree-of-freedom (SDOF) oscillators for five types of nonlinearities from the linear displacement peaks. The parameters of this model are estimated for various initial periods, nonlinearity types, and specific values of damping ratio, maximum possible ductility demand, and hysteretic parameters. Next, it is assumed that damage in each of the equivalent oscillators corresponding to different modes of vibration of the structure can be combined to quantify the structural damage. The hysteretic properties of these equivalent oscillators are estimated in the cases of 2-DOF and 3-DOF frames, and linear-peaks-based models for ductility demand and hysteretic energy demand are then used to estimate damage index for each of these oscillators. Finally, a combination rule is proposed to suitably combine these damage indices and thus estimate the extent of overall damage. A numerical study with the help of a suite of 100 ground motions illustrates how the proposed methodology estimates the damage levels of 2-DOF and 3-DOF example frames with strain-hardening bilinear and stiffness-degrading Riddell-Newmark type nonlinearities in the moment–curvature relationships of their column sections.
       
  • Sliding corner gusset connections for improved buckling-restrained braced
           steel frame seismic performance: Subassemblage tests
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Junxian Zhao, Ruobing Chen, Zhan Wang, Yi Pan Although brace-type hysteretic dampers have been widely adopted to mitigate structural damage under severe earthquakes, their performance was often limited by premature rupture of the welded corner gusset connection or its surrounding framing members due to additional frame action. Such a frame-gusset interaction was found more detrimental for buckling-restrained braced frames (BRBFs). A sliding corner gusset connection, which is connected to beam and column flanges by bolted end plates, but allows sliding deformations at the frame-gusset interfaces via employment of butyl rubber layers, is proposed to minimize such an interaction. Cyclic tests of three steel BRBF subassemblages, two with the proposed sliding configuration and another with the traditional welded one, were conducted to verify effectiveness of the proposed connection. Test results show that significant plastic damages were observed on the welded gusset connection and its surrounding beam. Seismic performance of this specimen was limited by significant out-of-plane and local buckling of the beam prior to brace rupture. Such an undesirable failure could be avoided by the proposed connection, in which the specimen with beam flange reinforcing plates exhibited satisfactory performance up to 4% drift, followed by additional 3% drift with 11 more cycles until brace rupture. The proposed connection is effective in reducing the seismic shear and flexural responses on the framing members, as well as the stress responses at the gusset interfaces. Structural behavior of the two types of gusset connection is compared and future research needs for design of these connections are provided.
       
  • Stochastic response of structures with hybrid base isolation systems
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Athanasios A. Markou, George Stefanou, George D. Manolis In 2004, two R/C residential buildings were retrofitted by using a hybrid base isolation system in Solarino, Sicily, and subsequently five free vibration tests were carried out in one of these buildings. The hybrid base isolation system combined high damping rubber bearings with low friction sliders. In terms of numerical modeling, a single-degree-of-freedom system is developed here with a new five-parameter trilinear hysteretic model for the simulation of the high damping rubber bearing, coupled with a Coulomb friction model for the simulation of the low friction slider. Furthermore, a shear beam type, four-degree-of-freedom model is used to numerically simulate the superstructure. Next, experimentally obtained data from the five initial-displacement, free vibration tests were used for the calibration of this six-parameter model describing the base isolation system. Following up on the model development, the present study employs Monte-Carlo simulations in order to investigate the effect of the unavoidable variation in the values of the six-parameter mechanical model on the response of both the hybrid base isolation system and the superstructure comprising the Solarino building. The calibrated parameters values from all the experiments are used as mean values, while the standard deviation for each parameter is deduced from the identification tests employing best-fit optimization for each experiment separately. The results of the Monte-Carlo simulations show that variation in the material parameters of the base isolation system produce a nonstationary effect in the response, which can be traced by the time evolution of its mean and standard deviation as computed from the response at different time instants. In addition, there is a magnification effect, since the coefficient of variation of the response, for most of the parameters, is larger than the coefficient of variation in the parameter values. The high level of nonlinearity in the base isolation system, as observed in the amplitude of vibration brought about by large initial displacements, helps explain the previously mentioned effects.
       
  • On collapse of the inner pipe of a pipe-in-pipe system under external
           pressure
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Mahmoud Alrsai, Hassan Karampour, Faris Albermani Collapse of the inner pipe of a pipe-in-pipe (PIP) system under external pressure is studied experimentally and numerically herein. Hyperbaric chamber test results of three PIP systems with identical inner pipes and different outer pipes are presented. It is observed that the geometric and material properties of the outer pipe affect the collapse pressure of the inner pipe. Using validated finite element analyses (FEA), a parametric study is conducted and collapse mechanisms of PIPs with various combinations of outer and inner pipes with practical range of diameter-to-thickness ratios (D/t) between 15 and 40 are discussed. Empirical expressions are proposed for the collapse pressure of the inner pipe (Pci), and its upper and lower bounds. The proposed empirical equation for Pci, is shown to agree well with the experimental results of the tested PIPs. Moreover, two distinctive modes of collapse in the inner pipe are identified and discussed.
       
  • Predicting the flutter speed of a pedestrian suspension bridge through
           examination of laboratory experimental errors
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Fabio Rizzo, Luca Caracoglia, Sergio Montelpare The paper investigates experimental error propagation and its effects on critical flutter speeds of pedestrian suspension bridges using three different experimental data sets: pressure coefficients, aerodynamic static forces and flutter derivatives. The three data sets are obtained from section model measurements in three distinct laboratories. Data sets are used to study three different geometries of pedestrian suspension bridges. Critical flutter speed is estimated using finite-element nonlinear analysis, numerical 2-DOF generalized deck model and 3-DOF full-bridge model. Flutter probability, contaminated by various experimental error sources, is examined. Experimental data sets are synthetically expanded to obtain two population sets of deck wind loads with 30 and 5 · 105 realizations, respectively. The first set is obtained using Monte-Carlo simulation approach, whereas the second one is determined using Polynomial chaos expansion theory and a basis of Hermite polynomials. The numerically-determined probability density functions are compared against empirical probability histograms (pdfs) by Kolmogorov-Smirnov tests.
       
  • Performance-based multi-hazard topology optimization of wind and
           seismically excited structural systems
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Arthriya Suksuwan, Seymour M.J. Spence The integration of topology optimization procedures into modern structural design frameworks is gaining interest as an innovative approach for achieving more efficient designs. To this end, probabilistic performance-based topology optimization frameworks have recently been proposed for the identification of optimal structural systems subject to extreme wind or seismic events considered in isolation. However, there are large geographic regions that are subject to both wind and seismic hazards. Therefore, the development of methods that can ensure that target performance metrics are met within a multi-hazard setting is a crucial step towards improving the reliability of structural systems.This paper is focused on proposing a simulation-centered performance-based topology optimization framework for the identification of optimal structural systems for multi-hazard wind and seismic environments. A probabilistic performance assessment framework is firstly proposed based on synergistically describing the performance of wind or seismically excited systems. Based on this framework, a multi-hazard topology optimization strategy is proposed. In particular, the methodology is centered on the definition of an approximate optimization sub-problem that not only decouples the simulation-based performance assessment from the optimization loop, but also transforms the dynamic and uncertain optimization problem into an explicit static and deterministic problem therefore enabling its efficient resolution using any gradient-based optimizer. Optimal lateral load resisting systems that rigorously meet the probabilistic performance constraints set within the multi-hazard environment are therefore identified. A case study is presented demonstrating the potential of the proposed framework.
       
  • Rolling shear: Test configurations and properties of some European soft-
           and hardwood species
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): T. Ehrhart, R. Brandner Shear stresses in planes perpendicular to the grain, so-called rolling shear stresses, need to be considered in the ultimate and serviceability limit state design of many timber structural elements. Knowledge about the rolling shear modulus and strength has further gained in importance since the invention and increased use of cross laminated timber (CLT). As a result of the orthogonal orientation of adjacent layers within CLT, rolling shear stresses develop when CLT is subjected to out-of-plane bending. Previous numerical and experimental studies on rolling shear are largely restricted to Norway spruce (Picea abies (L.) Karst.). In the present study, experimental investigations on the rolling shear properties were carried out on six timber species. The two investigated coniferous species were Norway spruce (Picea abies (L.) Karst.) and pine (Pinus sylvestris L.). Four deciduous species, namely European beech (Fagus sylvatica L.), European ash (Fraxinus excelsior L.), poplar (Populus tremula L.), and European birch (Betula pendula R.) were investigated. Furthermore, different board geometries and sawing patterns were investigated. In comparison to Norway spruce, all other investigated species featured higher rolling shear properties. In particular, these of European beech and European ash were roughly three-times higher. In agreement with previous findings, the aspect ratio (board width vs. board thickness) as well as sawing pattern were identified as main influencing parameters on the rolling shear properties. In addition to single board segments, multi-segment systems were experimentally tested and numerically investigated. Parallel systems consisting of either two or four board segments were tested to obtain information on potential system effects of laminations within single CLT cross layers regarding rolling shear strength and rolling shear modulus, i.e. stresses may be distributed depending on the local stiffness. This system effect may influence the shear strength, the shear modulus, and the failure behaviour compared to the results of single segment testing. Often, CLT elements consist of more than one cross layer. Layups can also feature parallel layers, however, usually with grain in direction of the main span direction. Some of these layups have a remarkable potential for two-dimensional load transfer. Thus, these commonly double or triple layers are exposed to rolling shear by stresses in the weak load transfer direction. As rolling shear failure of one of the cross layers in layups featuring alternating orthogonal layers as well as layups featuring some parallel layers leads to the ultimate failure of the entire element, such elements can be considered as serial systems with regard to the rolling shear strength and rolling shear modulus. In order to investigate the serial-parallel system behaviour, multi-segment systems consisting of 4 × 3 board segments were tested. The investigated systems should allow linking the results obtained from single element testing to the actual behaviour of CLT laminations and, subsequently, to give recommendations for rolling shear test configurations as well as related rolling shear properties. The outcomes show a good comparability between the results from out-of-plane bending tests on CLT elements featuring rolling shear failures and EN 408-alike shear tests conducted on board segments. The analysis of the within- and between-boards variation of rolling shear properties and density is also a part of this paper. The results of this study provide an overview of the rolling shear properties of tested European softwood and hardwood species. The investigated species are already in use, or have a significant potential to be used for construction purposes in the near future. The findings regarding the influential material- and product-related parameters contribute to a better understanding of the mechanical behaviour of timber subjected to rolling shear.
       
  • Practical displacement-based seismic design approach for PWF structures
           with supplemental yielding dissipators
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Tianshu Sun, Yahya C. Kurama, Jinping Ou This paper analytically investigates the design of supplemental metallic yielding dissipators to reduce the lateral displacements of pin-supported wall-frame (PWF) structures under high-intensity ground motions. The PWF system involves the use of a base-pinned structural wall to impose a first-mode dominant lateral drift profile on the coupled frame. Supplemental dissipative devices can be applied to increase the energy dissipation capacity of the coupled system by utilizing the relative displacements at the vertical wall-to-frame connections. This study proposes a displacement-based seismic design approach to determine the dissipator parameters so that the maximum roof drift of the structure under severe ground motions can be reduced to an allowable target roof drift. The validity of the proposed approach is verified based on nonlinear dynamic time-history analyses of three PWF structures with yielding dissipators. Besides, procedures to determine the minimum wall stiffness and strength are suggested for the preliminary design of the pin-supported wall. The dynamic behaviors of the example structures are critically evaluated, indicating that PWF system is suitable for the seismic retrofit project as well as for the development of novel sustainable earthquake resisting system.
       
  • Moment-rotation behavior of welded tubular high strength steel T joint
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Jarmo Havula, Marsel Garifullin, Markku Heinisuo, Kristo Mela, Sami Pajunen Based on recent studies, high strength steels (HSS) can be efficiently used in civil engineering, reducing the consumption of material and CO2 emissions. The present Eurocode contains the reduction coefficients (0.8 and 0.9 depending on the steel grade) for high strength steel joints. These reduction factors lead to the excessive consumption of material, making the usage of HSS for construction not as economically viable as it might be. The scope of this paper is to present experimental results dealing with the welded in-plane moment-loaded HSS joints. Twenty tests on square hollow section T joints were performed to observe their moment-rotation relationship, studying the following parameters: (1) bending resistance, (2) rotational stiffness, (3) ductility. The results show that the reduction factors are needed only for butt-welded joints, as well as for joints with small fillet welds and made of steel grades higher than S500. The required ductility was achieved by all specimens, even when using welds smaller than full-strength fillet welds. In addition, it was shown experimentally that fillet welds considerably increase the resistance and stiffness of joints.
       
  • Effects of sudden failure of shoring elements in concrete building
           structures under construction
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Manuel Buitrago, Juan Sagaseta, Jose M. Adam The most frequently used technique to construct reinforced concrete (RC) building structures is the shoring or propping of successive floors, in which the slabs are supported by the shores until the concrete acquires sufficient strength. A significant number of structural failures have been reported during construction in recent years leading in some cases to the progressive collapse of the whole structure. The collapse often starts with the local failure of a single element which could be due to errors in design or construction and/or due to accidental events. Although this is a well-recognized problem, studies on the effects of local failure in the shoring elements on the integrity of the shoring-structure system have not been carried out in the past. In this work advanced numerical finite element models were carried out of a three-storey RC building and its shoring system. Four scenarios of local failure were considered: sudden removal of a (1) shore, (2) joist and (3) complete shore line; and (4) incorrect selection of shores. The results indicated that the structure-shoring system was able to develop alternative load paths without dynamic amplification effects due to the large stiffness and redundancy of the system without compromising the integrity of the structure but leading to significant damage in the concrete slabs. Design recommendations are also given based on the results from this study, which pretend to be the first study to focus on the structural response and damage of a building structure under construction after the sudden failure of one or more shores.Graphical abstractGraphical abstract for this article
       
  • Axial compressive behavior of concrete columns with grade 600 MPa
           reinforcing bars
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Yizhu Li, Shuangyin Cao, Hang Liang, Xiangyong Ni, Denghu Jing An experimental study was performed to investigate the axial compressive behavior of concrete columns with Grade 600 MPa reinforcing bars. Nine large-scale concrete square columns were constructed and tested under pure axial loading. The effects of Grade 600 MPa transverse reinforcement with two different configurations (Type A and B) and amounts were evaluated. The behavior of columns was characterized by sudden spalling of concrete cover and ductility failure for well-confined columns, which was dominated by effective confinement index (keρshfyh/fc′). Columns confined by Grade 600 MPa transverse reinforcement exhibited the better performance in terms of strength, post-peak deformability, and toughness when compared with columns reinforced with conventional steel. The benefit of using Grade 600 MPa longitudinal bars on the axial load capacity of columns is limited, but it is beneficial to improve the post-peak deformability and toughness of columns with Type B configuration. A design expression is proposed for the amount of seismic confinement to ensure ductility behavior for columns, based on the effective confinement index.
       
  • Progressive collapse triggered by fire induced column loss: Detrimental
           effect of thermal forces
    • Abstract: Publication date: 1 October 2018Source: Engineering Structures, Volume 172Author(s): Thomas Gernay, Antonio Gamba In progressive collapse analysis, event-independent column loss is commonly used as a design scenario. Yet this scenario does not account for the fire-induced thermal forces that develop in case of a fire. The thermal forces may cause detrimental load redistributions in the structure, notably during the cooling phase. However, as the response of entire structures during the full course of fires until burnout has received little attention, these effects are not well established. The objective of this paper is to analyze the mechanisms of load redistribution in a structural system comprising a column subjected to localized fire, with a focus on the effects of the cooling phase. Numerical simulations by nonlinear finite element method are used, after validation against experimental data. The observed mechanisms result in tension building up in the fire-exposed column and overloading the adjacent columns in compression. Consequently, the damaged vertical member redistributes a force that is larger than the force initially carried. This can lead to failure of vertical members not directly affected by the fire and trigger a progressive collapse. These mechanisms are parametrically studied on a simple system composed of a column and a linear spring. Major parameters influencing the residual tensile force in the fire-exposed column are the maximum reached temperature and the relative stiffness of the remainder of the structure. The analysis of a twenty-story steel frame building under localized fire attacking one ground level perimeter column confirms the development of these mechanisms in a real design. The results have important implications as they question the validity of an event-independent design scenario for capturing the influence of column failure due to fire loading.
       
 
 
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