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  Subjects -> ENGINEERING (Total: 2244 journals)
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CIVIL ENGINEERING (179 journals)                     

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ACI Structural Journal     Full-text available via subscription   (Followers: 8)
Acta Polytechnica : Journal of Advanced Engineering     Open Access  
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 1)
Advances in Civil Engineering     Open Access   (Followers: 26)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 15)
Ambiente Construído     Open Access   (Followers: 1)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 21)
Architectural Engineering     Open Access   (Followers: 4)
Archives of Civil Engineering     Open Access   (Followers: 6)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access  
ATBU Journal of Environmental Technology     Open Access   (Followers: 1)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 4)
Baltic Journal of Road and Bridge Engineering     Full-text available via subscription   (Followers: 1)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 8)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 4)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 4)
Berkeley Planning Journal     Open Access   (Followers: 5)
Bioinspired Materials     Open Access   (Followers: 2)
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 13)
Building and Environment     Hybrid Journal   (Followers: 12)
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: 4)
Canadian Journal of Civil Engineering     Full-text available via subscription   (Followers: 9)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 5)
Case Studies in Nondestructive Testing and Evaluation     Open Access   (Followers: 3)
Case Studies in Structural Engineering     Open Access   (Followers: 1)
Cement and Concrete Composites     Hybrid Journal   (Followers: 13)
Challenge Journal of Structural Mechanics     Open Access   (Followers: 4)
Change Over Time     Full-text available via subscription   (Followers: 2)
Civil and Environmental Engineering     Open Access   (Followers: 6)
Civil And Environmental Engineering Reports     Open Access   (Followers: 4)
Civil and Environmental Research     Open Access   (Followers: 15)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 4)
Civil Engineering and Architecture     Open Access   (Followers: 8)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 2)
Civil Engineering and Technology     Open Access   (Followers: 4)
Civil Engineering Dimension     Open Access   (Followers: 5)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 193)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 8)
Computers & Structures     Hybrid Journal   (Followers: 25)
Concrete Research Letters     Open Access   (Followers: 2)
Construction Economics and Building     Open Access   (Followers: 1)
Construction Engineering     Open Access   (Followers: 5)
Construction Management and Economics     Hybrid Journal   (Followers: 18)
Construction Science     Open Access   (Followers: 1)
Constructive Approximation     Hybrid Journal  
Curved and Layered Structures     Open Access   (Followers: 1)
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal  
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 14)
Enfoque UTE     Open Access   (Followers: 1)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 5)
Engineering Structures     Hybrid Journal   (Followers: 11)
Engineering Structures and Technologies     Hybrid Journal   (Followers: 1)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 12)
Environmental Geotechnics     Open Access   (Followers: 3)
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 6)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 13)
Frattura ed Integrità Strutturale : Fracture and Structural Integrity     Open Access  
Frontiers in Built Environment     Open Access  
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 5)
Geomaterials     Open Access   (Followers: 1)
Geosystem Engineering     Hybrid Journal  
Geotechnik     Hybrid Journal   (Followers: 1)
Géotechnique Letters     Hybrid Journal   (Followers: 3)
HBRC Journal     Open Access   (Followers: 1)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal  
Indoor and Built Environment     Hybrid Journal   (Followers: 1)
Infrastructure Asset Management     Hybrid Journal   (Followers: 1)
Ingenio Magno     Open Access  
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 15)
International Journal for Service Learning in Engineering     Open Access  
International Journal of 3-D Information Modeling     Full-text available via subscription   (Followers: 2)
International Journal of Advanced Structural Engineering     Open Access   (Followers: 7)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 6)
International Journal of Condition Monitoring     Full-text available via subscription   (Followers: 1)
International Journal of Construction Engineering and Management     Open Access   (Followers: 4)
International Journal of Geo-Engineering     Open Access  
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription   (Followers: 1)
International Journal of Masonry Research and Innovation     Hybrid Journal  
International Journal of Pavement Research and Technology     Open Access   (Followers: 1)
International Journal of Protective Structures     Full-text available via subscription   (Followers: 4)
International Journal of Steel Structures     Hybrid Journal   (Followers: 2)
International Journal of Structural Engineering     Hybrid Journal   (Followers: 7)
International Journal of Structural Integrity     Hybrid Journal  
International Journal of Structural Stability and Dynamics     Hybrid Journal   (Followers: 5)
International Journal of Sustainable Built Environment     Open Access   (Followers: 3)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 7)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 3)
Journal of Accessibility and Design for All     Open Access   (Followers: 6)
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 15)
Journal of Building Engineering     Hybrid Journal  
Journal of Building Materials and Structures     Open Access  
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 5)
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 6)
Journal of Civil Engineering and Management     Hybrid Journal   (Followers: 6)
Journal of Civil Engineering and Science     Open Access   (Followers: 6)
Journal of Civil Engineering Research     Open Access   (Followers: 5)
Journal of Civil Society     Hybrid Journal   (Followers: 3)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 3)
Journal of Composites     Open Access   (Followers: 68)
Journal of Composites for Construction     Full-text available via subscription   (Followers: 12)
Journal of Computing in Civil Engineering     Full-text available via subscription   (Followers: 21)
Journal of Construction Engineering     Open Access   (Followers: 4)
Journal of Construction Engineering and Management     Full-text available via subscription   (Followers: 19)
Journal of Construction Engineering, Technology & Management     Full-text available via subscription   (Followers: 2)
Journal of Constructional Steel Research     Hybrid Journal   (Followers: 6)
Journal of Earth Sciences and Geotechnical Engineering     Open Access   (Followers: 1)
Journal of Fluids and Structures     Hybrid Journal   (Followers: 4)
Journal of Frontiers in Construction Engineering     Open Access   (Followers: 3)
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: 8)
Journal of Infrastructure Systems     Full-text available via subscription   (Followers: 15)
Journal of Legal Affairs and Dispute Resolution in Engineering and Construction     Full-text available via subscription   (Followers: 4)
Journal of Marine Science and Engineering     Open Access   (Followers: 1)
Journal of Materials in Civil Engineering     Full-text available via subscription   (Followers: 10)
Journal of Multifunctional Composites     Full-text available via subscription   (Followers: 2)
Journal of Nondestructive Evaluation     Hybrid Journal   (Followers: 7)
Journal of Offshore Structure and Technology     Full-text available via subscription  
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  
Journal of Solid Waste Technology and Management     Full-text available via subscription  
Journal of Structural Engineering     Full-text available via subscription   (Followers: 35)
Journal of Structural Fire Engineering     Full-text available via subscription   (Followers: 6)
Journal of Structures     Open Access   (Followers: 2)
Journal of Sustainable Design and Applied Research in Innovative Engineering of the Built Environment     Open Access   (Followers: 1)
Journal of the South African Institution of Civil Engineering     Open Access   (Followers: 4)
KSCE Journal of Civil Engineering     Hybrid Journal   (Followers: 1)
Latin American Journal of Solids and Structures     Open Access   (Followers: 1)
Materiales de Construcción     Open Access  
Mathematical Modelling in Civil Engineering     Open Access   (Followers: 3)
Nondestructive Testing And Evaluation     Hybrid Journal   (Followers: 11)
Obras y Proyectos     Open Access   (Followers: 1)
Open Journal of Civil Engineering     Open Access   (Followers: 3)
Photonics and Nanostructures - Fundamentals and Applications     Hybrid Journal   (Followers: 2)
Practice Periodical on Structural Design and Construction     Full-text available via subscription   (Followers: 4)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 6)
Proceedings of the Institution of Civil Engineers - Civil Engineering     Hybrid Journal   (Followers: 11)
Proceedings of the Institution of Civil Engineers - Management, Procurement and Law     Hybrid Journal   (Followers: 6)
Proceedings of the Institution of Civil Engineers - Municipal Engineer     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Civil Engineers - Structures and Buildings     Hybrid Journal   (Followers: 3)
Random Structures and Algorithms     Hybrid Journal   (Followers: 3)
Recent Trends In Civil Engineering & Technology     Full-text available via subscription   (Followers: 2)
Research in Nondestructive Evaluation     Hybrid Journal   (Followers: 4)
Revista IBRACON de Estruturas e Materiais     Open Access   (Followers: 1)
Road Materials and Pavement Design     Hybrid Journal   (Followers: 6)
Russian Journal of Nondestructive Testing     Hybrid Journal   (Followers: 2)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 54)
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  
Steel Construction - Design and Research     Hybrid Journal   (Followers: 1)
Structural and Multidisciplinary Optimization     Hybrid Journal   (Followers: 7)
Structural Concrete     Hybrid Journal   (Followers: 9)
Structural Control and Health Monitoring     Hybrid Journal   (Followers: 6)
Structural Engineering International     Full-text available via subscription   (Followers: 9)
Structural Safety     Hybrid Journal   (Followers: 7)
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: 9)
Structures     Hybrid Journal  
Study of Civil Engineering and Architecture     Open Access   (Followers: 7)
Superlattices and Microstructures     Hybrid Journal   (Followers: 2)
Surface Innovations     Hybrid Journal  
Technical Report Civil and Architectural Engineering     Open Access  
Teknik     Open Access  
The IES Journal Part A: Civil & Structural Engineering     Hybrid Journal   (Followers: 5)
The Structural Design of Tall and Special Buildings     Hybrid Journal   (Followers: 5)
Thin Films and Nanostructures     Full-text available via subscription   (Followers: 1)
Thin-Walled Structures     Hybrid Journal   (Followers: 1)
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: 6)
Water Science & Technology     Partially Free   (Followers: 20)
Water Science and Technology : Water Supply     Partially Free   (Followers: 21)

           

Journal Cover Structural Concrete
  [SJR: 0.739]   [H-I: 9]   [9 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1464-4177 - ISSN (Online) 1751-7648
   Published by John Wiley and Sons Homepage  [1597 journals]
  • Comparison of Main Models for Size Effect on Shear Strength of Reinforced
           and Prestressed Concrete Beams
    • Abstract: This paper presents a critical comparison of the existing code provisions for shear strength of concrete beams. The comparison is based on the computer filtering of inevitable statistical bias from the available multivariate database on shear strength, on the examination of the predicted size effects on shear strength and their underlying hypotheses, and on the results of recent high‐fidelity numerical simulations of shear failure. In addition to examining the existing models, the present comparison also provides several key considerations for testing the scientific soundness of any model of shear failure of concrete beams, which is necessary for future revisions of the design code provisions.
      PubDate: 2016-05-17T09:05:29.930795-05:
      DOI: 10.1002/suco.201500126
       
  • Nanoscale modifier as an adhesive for hollow microspheres to increase the
           strength of high‐strength lightweight concrete
    • Authors: Aleksandr Sergeevich; Evgenij V. Korolev, Vladimir A. Smirnov
      Abstract: The paper presents the results of the study of physical‐mechanical and operational properties of the high‐strength lightweight concrete and influence of nanoscale modifier on these properties. The nanomodifier and method of its application to improve the properties of lightweight concrete with hollow microspheres at 10–25% was proposed. It is shown that the control process of the structure formation of the cement stone which leads to the acceleration of the hydration of portland cement and the formation an additional amount of calcium hydrosilicates at the phase boundary during reaction of nanoscale silicon‐oxygen shell grafted onto the surface of the microspheres with the cement hydration products (calcium hydroxide). This provides growth of operational properties. The high‐strength lightweight concrete with an average density less than 1500 kg/m3 is characterized by strength more than 40 MPa (specific strength Rspã30 MPa). The optimum range of concentrations of the precursor for preparation of nanomodifier is defined to be 1.25≤[Na+]/[Cl‐]≤2.5. We can conclude that the developed compositions has dense and strong structure which can resist intense cracking. Application of nanoscale modifier allows to increase the elastic modulus at 13–36% (it is equal to 6.2–8.5 GPa depending on the average density), to decrease the water absorption (to 1%) and to improve the water resistance (coefficient of water resistance is more than 0.95) and freeze‐thaw resistance (up to F300). The nanomodified high‐strength lightweight concrete has beneficial values of heat‐conduction coefficient (0.48‐0.70 W/(m·°C)), temperature conductivity coefficient ((3.43–4.04)·10‐7 m2/s) and specific heat capacity (1080–1175 J/(kg·°C)). It allows us to consider this concrete as a multifunctional material with both structural and thermal insulation properties.
      PubDate: 2016-05-17T09:05:25.314655-05:
      DOI: 10.1002/suco.201500048
       
  • Increasing the flexural capacity of RC beams using steel angles and
           pre‐tensioned stainless steel ribbons
    • Authors: Piero Colajanni; Antonino Recupero, Nino Spinella
      Abstract: This article presents an experimental campaign on reinforced concrete beams retrofitted with steel angles and pre‐stressed stainless steel ribbons to increase their flexural strength and ductility. Two different configurations of the steel ribbon were designed, and two companion specimens for each type considered were subjected to four point bending test to facilitate a direct comparison in the analysis of the effectiveness of the retrofitting technique. The influence of longitudinal steel angles and transverse stainless steel ribbons is analyzed, and the concrete confinement due to stainless steel ribbons examined. The strengthened beams show remarkable increments in flexural strength and ductility with respect to the as‐built beam. Moreover, a simple cross sectional model was adopted to calculate the flexural strength; then sophisticated numerical tools were used to reproduce both the experimental load‐displacement curve and crack pattern for each specimen.
      PubDate: 2016-04-11T07:40:57.090873-05:
      DOI: 10.1002/suco.201500187
       
  • The monitored and theoretical ultimate moment and ductility of
           pre‐tensioned HSSCC bridge girders
    • Authors: Mohammad Maghsoudi; Aliakbar Maghsoudi, Arash Ali Heshmati
      Abstract: Self‐compacting concrete (SCC) is defined as highly flowable and none‐segregating concrete that does not require mechanical vibration during its application. The load test of bridge girders was investigated on constructed full scale T‐beams of pre‐tensioned high strength self‐compacting concrete (PHSSCC). The girders were monitored by fixing different types of sensors at different locations. Results of ultimate moment are compared to evaluate if such girders can be designed using AASHTO Load and Resistance Factor Design (LRFD) Specifications; AASHTO Standard Specifications for Highway Bridges (STD) and the PCI Bridge Design Manual are for structures constructed using conventional (none vibrated) concrete. It is concluded that good agreement in results exists for the two methods. Investigations (theoretical and experimental) are needed on the issue of ductility in structural prestressed elements constructed in seismic zones or even, the issue of high strength in SCC. These have been studied here too, and it has been concluded that, suitable ductility for this type of structure, as would be needed in seismic regions, can be achieved.
      PubDate: 2016-04-11T07:40:43.547163-05:
      DOI: 10.1002/suco.201500219
       
  • Bond Behaviour of Straight, Hooked, U‐Shaped and Headed Bars in
           Cracked Concrete
    • Abstract: Most classical investigations on bond properties in reinforced concrete have been performed on the basis of pull‐out tests, where a reinforcement bar is pulled out from an uncracked concrete cylinder, prism or cube. In these tests, bond is governed by the concrete strength and bar surface properties of the reinforcement (bond index, rib geometry) or by the splitting strength of concrete (concrete cover). In the latter case, failure in bond occurs due to uncontrolled cracking of the concrete specimen. Contrary to these fundamental tests, in many structural members, bond is activated within already cracked concrete. This is particularly relevant for the reinforcement in beams and slabs (both for the flexural and transverse reinforcement), as the reinforcing bars might be located at planes where flexural cracks develop. The opening of these cracks along the reinforcement is nevertheless not uncontrolled (as opposed to splitting failures), but it is governed by the bending deformations. The bond properties and strength of the reinforcement in actual members are, therefore, influenced by the opening of these cracks and are potentially different from those observed from classical pull‐out tests. The present paper aims to address this topic by presenting the results of an experimental investigation on 89 monotonic pull‐out tests performed on cracked ties. The opening of the cracks was controlled while transverse bars ‐located in the plane of these cracks‐ were pulled out from the specimens. The tests were performed for crack openings ranging from 0.2 mm to 2.0 mm in order to cover conditions both at serviceability and ultimate limit states. The results show a very significant influence of in‐plane cracking on both the strength and bond‐slip stiffness, with decreasing mechanical performance for increasing crack openings. The performance of different actual anchorage types (straight, hooked, U‐shaped and headed bars) ‐ generally characterized through force ‐slip relationships‐ is finally analytically investigated and compared to the test results.
      PubDate: 2016-04-11T07:40:30.474197-05:
      DOI: 10.1002/suco.201500199
       
  • Flexural Strengthening and Repair of RC Slabs by Adding a New RC Layer
    • Abstract: The present paper summarizes the findings of an experimental program dedicated to investigate a strengthening/repair technique, the introduction of a new RC layer to the existing slab. Six RC slabs, composed of twelve cantilever and six interior spans, were tested under monotonic transverse loading. The behavior of statically determinate cantilever spans and indeterminate interior spans was examined by comparing the test results of these specimens to the results of reference slabs, in which the existing and additional layers were cast monolithically. The influence of recovering the permanent slab deformations before repair and the spacing of the shear connectors between the existing and additional layers were investigated. The tests indicated that recovering the permanent deformations of a slab before repair reduces its rigidity substantially while having little influence on the ultimate load. Furthermore, debonding of the reinforcement was observed to decrease the load capacities and rigidities of the slabs considerably.
      PubDate: 2016-04-11T07:36:02.315007-05:
      DOI: 10.1002/suco.201500182
       
  • EXPERIMENTAL BEHAVIOUR AND DEFLECTIONS OF LOW STRENGTH CONCRETE BEAMS
           REINFORCED BY FRP BARS
    • Authors: CONFRERE ADELINE; Laurent Michel, Emmanuel Ferrier, Gilles Chanvillard
      Abstract: The primary objective of this new study on Fibre‐Reinforced Polymer (FRP)‐reinforced concrete (RC) beams is to evaluate the mechanical performance of RC beams made of low strength concrete internally reinforced by FRP. The association of FRP rebar with low compressive strength concrete is desirable to avoid the accelerated corrosion processes that could occur with steel rebar. For this purpose, an experimental programme was designed to identify the failure modes and bending behaviour. The experimental results are compared with equations from ACI 440.1R‐06, CSA S806‐12 and other design codes, as well as with other results from a review of the literature. The comparisons indicate that resistant moment is well predicted by codes for flexural failure. At ultimate loads, deflection of the beams is further underestimated compared to that of beams reinforced by higher compressive strength concrete. An analytical simulation of 690 beams indicates that deflection is the major limiting criterion at the Service Limit State. Finally, the problem formulation of the optimal FRP design for reinforced concrete beams can be cast into a programming problem. The space of feasible design solutions and the optimal solutions can be obtained using only a reduced number of design variables and an existing design method.
      PubDate: 2016-04-11T07:35:47.531103-05:
      DOI: 10.1002/suco.201500046
       
  • New structural joint by rebar looping applied to staged box girder bridge
           construction. Static tests
    • Authors: Sergi Villalba; Joan R. Casas
      Abstract: This paper shows the design, development and experimental checking of a modified type of structural joint with limited length between concrete segments cast “in‐situ”. The design concept is based on the development length of an anchorage hook stiffened by transverse reinforcement bars and is particularly suited for the case of in‐situ construction of staged box girder bridges, seeking to the possibility of using lighter scaffolding. The studies focusing on the strength, stiffness and serviceability of the proposed joint are presented. The research work comprises the bending behaviour of reinforced concrete slabs with loop joints with regard to the diameter of loop bar, loop joint width and ultimate and fatigue load. The results are compared to the behaviour of reinforced concrete slabs without joints. A total of 16 slabs were tested by static and fatigue loading tests. The present paper evaluates the flexural behaviour under static loading test. The results of fatigue tests have also shown an excellent performance. In the static tests, crack width and crack pattern were observed at service load levels, and the ultimate behaviour was evaluated by means of up to failure tests. From the test results, the service performance of the loop joints was confirmed similar to slabs without joints. The static loading tests confirm the good performance and effectiveness of this loop joint type under static loads. Details of loop joints design criteria are also suggested.
      PubDate: 2016-04-11T07:35:35.207835-05:
      DOI: 10.1002/suco.201500117
       
  • Variation in fibre volume and orientation in walls: Experimental and
           numerical investigation
    • Abstract: Previous research with fibre‐reinforced slab elements has shown that the surface roughness of formwork and the presence of rebars affect fibre orientation and fibre volume distribution. This paper discusses the orientation and volume distribution of steel fibres in wall elements cast from a single point. In particular, the effect of formwork tie bars on fibre orientation and distribution was studied. To quantify the fibre orientation and distribution, numerical simulations and X‐ray computed tomography were applied, and the mechanical performance was determined using three‐point bending tests on sawn beams. The Thorenfeldt model (applied in the Norwegian proposal of the new fibre‐reinforced concrete guideline) was used to estimate the residual flexural tensile strength based on fibre orientation and distribution. The simulation results show that the fibre orientation can be related to the flow pattern. The results indicate a large variation in fibre orientation, which was experimentally confirmed. The fibre volume distribution was mostly uniform, except for an area with fewer fibres at the casting point. The large variation in fibre orientation was reflected by a large variation in residual flexural tensile strengths. Weak zones due to anisotropic fibre orientation caused by formwork tie bars were observed.
      PubDate: 2016-03-16T09:05:39.832375-05:
      DOI: 10.1002/suco.201500060
       
  • Experiments about load bearing behaviour of lightweight sandwich beams
           using textile reinforced and expanded polystyrene concrete
    • Authors: Viet Anh Nguyen; Frank Jesse, Manfred Curbach
      Abstract: Textile reinforced concrete (TRC) it is a combination of small grain high performance concrete (HPC) and high strength textile reinforcement. TRC allows thin layers and has high tensile and compressive strength. In this paper, TRC was used for the face layers and it was combined with a core of lightweight expanded polystyrene concrete (EPC) to create lightweight sandwich beams without special joint reinforcement to connect the layers. The experimental testing of the load bearing behaviour of this kind of sandwich beams, along with the influence of the shear span to depth ratio (aȏd) as observed during 3‐point and 4‐point bending tests will be summarized. The failure behaviour of the sandwich beams is influenced by the shear span to depth ratio, the type of bending test and the tensile capacity of the TRC layer. The diagonal tension failure occurred in experimental beams with 2.6≤ aȏd ≤ 5.2 for 3‐point bending tests and 3.1 ≤ aȏd ≤ 4.1 for ‐point bending tests. The shear strength of the beams could be conservatively estimated according to the current European standards.
      PubDate: 2016-03-16T09:01:47.877063-05:
      DOI: 10.1002/suco.201500156
       
  • ANALYTICAL MODELING OF BOND STRESS AT STEEL‐CONCRETE INTERFACE DUE
           TO CORROSION
    • Authors: Luaay Hussein; Lamya Amleh
      Abstract: An analytical model for bond stresses at the corroded steel‐concrete interface in a reinforced concrete is proposed. The concrete around the corroded bar is modeled as a thick‐walled cylinder, consisting of an inner cylinder of an anisotropic material, and an outer cylinder made of an isotropic material, and subjected to internal pressure exerted from the growth of corrosion products on the concrete wall at the interface. A frictional model is used to combine the action of confining pressure from the radial pressure produced by principal bar ribs, and the pressure resulted from expansion of corrosion products. The analysis results using the proposed model showed good agreement with the experimental results from several researchers.
      PubDate: 2016-03-16T09:01:45.20972-05:0
      DOI: 10.1002/suco.201500109
       
  • Contents: Structural Concrete 1/2016
    • PubDate: 2016-03-09T11:38:17.376787-05:
      DOI: 10.1002/suco.201670015
       
  • Cover Picture: Structural Concrete 1/2016
    • Abstract: The Tsubasa Bridge in Neak Loeung is a three span stay cable bridge crossing the Mekong River in Cambodia. With a main span of 640 m the bridge is not only a new landmark of the region, but also Cambodia's longest bridge. Construction of this bridge was due to the increasing congestion on the important National Highway 1 in Cambodia, which connects the capital of Phnom Penh with the Bavet border crossing to Vietnam. DYWIDAG Stay Cables as well as Strand Post‐Tensioning Systems and Bar Post‐Tensioning Systems support the construction of the Tsubasa Bridge. (© DSI, see p. A5–A6)
      PubDate: 2016-03-09T11:38:12.334059-05:
      DOI: 10.1002/suco.201670011
       
  • Influence of Reinforcement Type on Macrocrack Propagation under Sustained
           Loading in Steel Fibre Reinforced Concrete
    • Abstract: To meet the growing challenges of sustainability, it is necessary to control and anticipate cracking problems of structures under sustained loadings. At the structural scale, very little information is available regarding the combined effect of SFRC and reinforcement under sustained flexural loading. This paper presents the results of four flexural creep tests on steel fibre reinforced concrete large beams reinforced with fibres only or in combination with unbonded prestressing strands, bonded prestressing strands, or traditional reinforcing bars. The main objective was to assess the influence of the reinforcement type on crack propagation, crack openings, and compliance evolution under sustained loading in SFRC. The results show that the thriving mechanism of crack propagation is the same for all beams, regardless of the reinforcement type, and is therefore governed by type of fibre concrete.
      PubDate: 2016-03-07T10:13:00.703234-05:
      DOI: 10.1002/suco.201500069
       
  • On the reliability of design approach for FRC structures according to
           Model Code 2010: the case of elevated slabs
    • Authors: Marco Di Prisco; Paolo Martinelli, Benoit Parmentier
      Abstract: The paper focuses on the reliability of the design approach proposed in Model Code 2010 for the estimation of the ultimate capacity of fibre‐reinforced concrete (FRC) elevated slabs on the basis of different tests for material characterisation. The fracture properties of the material are determined through three‐point bending tests on notched beams, and through double edge wedge splitting (DEWS) tests carried out on cylinders cored in the full‐size test structure. As a case study, an FRC elevated flat slab is considered, consisting of 9 bays (panels) of a 6×6 m2 dimension and supported by sixteen circular concrete columns having a thickness of 0.2 m and a full‐size of 18.3×18.3 m2. The ultimate bearing capacity of the slab experimentally determined is compared with the design value predicted by means of a procedure based on limit analysis following the Model Code 2010. The results show that the method proposed in the Model Code 2010 using the characteristic values and the classification is reliable. Even if the tests are affected by a significant standard deviation and the two experimental campaigns with 3‐point bending tests give a significant difference from class “5c” to class “3e”, the structural test presents a bearing capacity that is always larger than the predicted one, which considers a safety coefficient for the material γF = 1.5.
      PubDate: 2016-03-07T10:12:29.915913-05:
      DOI: 10.1002/suco.201500151
       
  • DESIGN PROCEDURE OF PRECAST FIBER REINFORCED CONCRETE SEGMENTS FOR TUNNEL
           LINING CONSTRUCTION
    • Authors: Fabio Di Carlo; Alberto Meda, Zila Rinaldi
      Abstract: A procedure for the design of precast tunnel segments for mechanical excavated tunnel lining in fiber reinforced concrete, without any traditional steel reinforcement, is presented herein. Both Ultimate and Serviceability Limit States are considered, as well as structural checks at different construction stages of the segment, including demoulding, positioning on floor, storage, transportation, handling and the final stage concerning the loads due to the ground pressure. The structural checks are performed by means of bending moment – axial force interaction envelopes for both the considered Limit States, once defined the constitutive relationship of the material in each stage. Traditional interaction envelopes are drawn for the Ultimate Limit State check, while for Serviceability Limit State check, envelopes obtained by limiting the maximum crack opening and the maximum concrete compressive stress are proposed. The shear action is also accounted for by reducing the bending moment – axial force envelope. The possibility of having an assisted by test procedure for particular loading situation is also proposed. Finally, a case study related to a precast steel fiber reinforced concrete segment is analysed in order to clarify the procedure and to show practically how to define the actions and to evaluate the interaction envelopes.
      PubDate: 2016-03-07T10:12:16.573549-05:
      DOI: 10.1002/suco.201500194
       
  • Reinforced concrete thin wall dome after eighty years of operation in
           maritime climate environment
    • Abstract: The paper presents a description of the construction elements of the Gdynia Seaport main hall dome. First of all, it provides information about the dome's structure technical conditions. Secondly, it treats about the strength analysis of the thin‐walled reinforced concrete dome covering. Throughout the last 80 years the building was exposed to an unfavorable marine climate. The analysis of the state of stress and deformations of several construction elements was carried out using a special model worked out with help of the FEM considering the combination of loads: dead weight, wind and snow, as well as the additional combination: dead weight and hurricane wind of velocity 200 km/h (55.5 m/s). The computed results of static quantities were also obtained according to F. Dischinger's method which was used in design of the RC Gdynia Seaport dome in 1932. The computational analysis and the assessment of the technical state made it possible to make a decision concerning further safe operation of the building. To sum up, it can be concluded that the results obtained with the FEM analysis and the analysis of the technical state 80‐years old dome made it possible to carry out an assessment of the factor of safety of the dome's reinforced concrete elements. That in turn made it possible to come to a decision on the possibility of its further operation without causing any major local demolition. What is more, it permitted to construct a new dome after tearing‐down of the old one.
      PubDate: 2016-03-07T10:12:02.621839-05:
      DOI: 10.1002/suco.201500180
       
  • Reliability‐Based and Life‐Cycle‐Cost Oriented Design
           Recommendations for Prestressed Concrete Bridge Girders
    • Authors: Makato Yanaka; Seyed Hooman Ghasemi, Andrzej S. Nowak
      Abstract: There are several methods available to decide on appropriate design recommendations against corrosion of reinforcing steel in prestressed concrete bridge girders. With respect to chloride‐induced corrosion, in the present study two methods are considered. The first one is based on the target probability of corrosion initiation and the initial cost. The other method is based on the life cycle cost that includes the initial cost, maintenance cost, and expected failure cost. This paper deals with the development of recommendations for durability design of structures in marine environments from the reliability point of view, taking into consideration of the life cycle cost of a structure. In order to approach the problem, the chloride diffusion coefficient of a cracked area under service load is obtained considering opening and closing motion of cracks. Utilizing the diffusion coefficient of a cracked area, the development over time of the chloride concentration at the surface of reinforcement can be predicted. This information is used to quantify probability of initiation of corrosion of prestressing steel as well as the distribution of life cycle cost. Based on the findings recommendations for durability design in various exposure environments are developed.
      PubDate: 2016-03-07T10:11:49.622723-05:
      DOI: 10.1002/suco.201500197
       
  • Cyclic behavior of interior reinforced concrete beam‐column
           connection with Self‐Consolidating Concrete
    • Authors: Jalal Salehi Mobin; Mohammad Taghi Kazemi, Nader K.A. Attari
      Abstract: A significant amount of research in Self‐Consolidating Concrete (SCC) technology has been devoted to evaluate the suitability of the material to be used in structural applications. However, more researches are required to confirm the adequacy of SCC structural members to resist gravity and seismic loads. This study focuses on the experimental investigation of the seismic performance of interior reinforced concrete beam‐column connections with SCC. In this experimental study, four beam‐column connection specimens, three SCC and one normally vibrated concrete (NC), were designed. Factors such as the concrete type (SCC and NC) and axial load ratio (0%, 7.5% and 15% of column section capacity) were assumed to be the variables in designing the specimens. Beam‐column connections made with NC and SCC were studied and compared under reversed cyclic loading. The performance of SCC specimens is comparable with NC specimens in terms of strength, displacement and ductility, but SCC specimens show lower energy dissipation capacity.
      PubDate: 2016-02-25T03:12:16.231596-05:
      DOI: 10.1002/suco.201500133
       
  • ESTIMATION OF CORROSION ATTACK IN REINFORCED CONCRETE BY MEANS OF CRACK
           OPENING
    • Authors: Carmen Andrade; Alessandro Cesetti, Giuseppe Mancini, Francesco Tondolo
      Abstract: The corrosion of reinforcements in concrete is the most common degradation phenomenon of reinforced concrete structures. Reinforced concrete elements subjected to corrosion generally crack due to the expansive nature of oxides. A very important task is to estimate the corrosion level using a non‐destructive method, in order to establish both the actual safety of the structure and a priority intervention plan. Many researches have studied the relationship between the corrosion phenomenon and the corresponding crack openings and their evolution; several statistical analyses, based on test data from experimental campaigns, under a wide range of test conditions, are available. The present work tries to contribute to the finding a relationship between the crack opening and the amount of corrosion induced in the reinforcing bars. The result of the analysis is that only a reduced number of tests can be used to establish an empirical model on a reliable test data set. A simple relationship between crack opening and corrosion penetration is not recommended, due to the different parameters that are able to influence this correlation. Therefore two fundamental parameters, that is, the ratio of the concrete cover to the rebar diameter and concrete strength have also been considered. The considerations made on these parameter test results have been rearranged, and the result is that a formulation has been found that shows reduced scatter.
      PubDate: 2016-02-25T03:11:08.780739-05:
      DOI: 10.1002/suco.201500114
       
  • Flexural capacity enhancement of rectangular high‐strength concrete
           columns confined with post‐tensioned steel straps: Experimental
           investigation and analytical modeling
    • Abstract: Load carrying capacity and deformability of concrete column can be substantially enhanced after confined with post‐tensioned steel‐straps. As the interests in the high‐strength concrete (HSC) grow among structural engineers and researchers due to its superior performance, this confining technique is extended to HSC columns with the hope that it can eliminate the undesired properties of HSC especially its brittleness. However, experimental studies in confined HSC columns subjected to eccentric loads is comparatively limited. It can be observed in the past research that most of the studies in external confinement were conducted on small‐scale normal‐strength concrete (NSC) cylinders subjected to concentric loads. Since most of the columns are subjected to eccentric loads in reality, the scarcity of test data has prevented the full potential use of this confining technique. In this paper, this confining technique is termed as steel‐strapping tensioning technique (SSTT) hereafter for brevity. Nine HSC columns were tested under eccentric loads. The specimens were grouped into three groups with each group had an unconfined HSC column as control specimen, a two layer SSTT‐confined HSC column and a four layer confined HSC column. The experimental results show that the flexural capacities of HSC columns can be enhanced with SSTT. The deformability of confined HSC columns is significantly improved with the confinement provided.
      PubDate: 2016-02-25T03:10:53.655428-05:
      DOI: 10.1002/suco.201500123
       
  • Derivation of design rules for innovative shear connectors in steel
           concrete composites by systematic use of nonlinear Finite Element Analysis
           (FEA)
    • Abstract: Today, the development of novel shear connectors for steel‐concrete‐composites is accompanied by an extensive amount of experimental investigations, obligatory to propose suitable design formula and to carve out their limitations of use. Using the example of the so called pin‐connector, the present paper illustrates to which degree validated finite element models of novel shear connectors can be used to substitute expensive and time‐consuming shear tests and in which manner these finite element models can support the deduction of design concepts. The regarded pin connector was developed for the connection of steel sections with very slender high strength concrete slabs, in which conventional shear connectors like headed studs cannot be applied due to the limited embedment depth. In order to clarify the shear behavior and load carrying mechanisms of these novel connectors, non‐linear finite element models have been set up, using the commercial FE‐Software ABAQUS. The numerical simulations were validated by shear tests. Subsequently, the validated models were used to perform systematic parametric studies. The paper documents the numerical results and finally explains the stepwise development of an entire engineering model to determine the longitudinal shear capacity of small‐scaled pin connectors including all required limitations of use. The proposed modeling strategy and the methodology for the deduction of design rules can be transferred and assigned to other types of shear connectors.
      PubDate: 2016-02-18T08:59:42.75961-05:0
      DOI: 10.1002/suco.201500217
       
  • Recent Advances in Experimental Study on Mechanical Behaviour of Natural
           Fibre Reinforced Cementitious Composites
    • Authors: He Tian; Y.X. Zhang, Chunhui Yang, Yining Ding
      Abstract: This paper presents a review of the recent research and development of natural fibre‐reinforced concrete (NFRC). The recent developments on NFRC reinforced with different types of natural fibres, such as sisal fibre, bagasse fibre, coir fibre, banana fibre, eucalyptus fibre, flax fibre, jute fibre and pinus radiate fibre are covered. Natural fibres and their modification methods are firstly introduced, and the development history of natural fibre reinforced concrete and the relevant research on the mechanical behaviour of NFRC in both short term and long term are reviewed. The applications of NFRC are also summarized.
      PubDate: 2016-02-18T08:59:28.145913-05:
      DOI: 10.1002/suco.201500177
       
  • Development of stiffness and ultrasonic pulse velocity of dynamically
           loaded concrete
    • Authors: Christoph von der Haar; Steffen Marx
      Abstract: Damage processes in dynamically loaded concrete structures depend on the number and amplitude of applied load cycles. Damage evolution is linked to a reduction in concrete stiffness, and it is thought that this reduction causes stress redistributions at the component level, which have a favorable impact on the service life of the structure. Until now, the stiffness reduction and stress redistribution have never been successfully measured in laboratory tests or in situ. It is only known that the real service life is greater than the calculated one and that indicators of stiffness reduction, such as the component deflection, increase with the number of applied load cycles. Ultrasonic measurement techniques are considered to be well suited for detecting degradation processes caused by dynamic loading. By using ultrasonic pulse velocity measurements, it is expected that the stiffness reduction of dynamically loaded concrete structures can be recorded reliably. Against this background, fatigue tests on small‐scale concrete specimens were performed. The aim of the tests was to understand the correlation between the observed stiffness degradation of the specimens and the results of ultrasonic pulse velocity measurements and to estimate the potential of ultrasonic pulse velocity measurements for continuous structural health monitoring.
      PubDate: 2016-02-18T08:59:15.140464-05:
      DOI: 10.1002/suco.201600007
       
  • Behaviour of reinforced concrete rectangular sections based on tests
           complying with seismic construction requirements
    • Abstract: The prediction of the seismic behaviour of reinforced concrete elements by using numerical models has become a field of growing interest in recent years, due to the importance of adequately knowing the effects induced by seismic loads applied to reinforced concrete structures. The simulation of the hysteretic behaviour of the plastic hinges generated in the structure when the seismic load acts requires the use of models capable of describing the sectional behaviour of structural members. Thus, the main objective of the present paper is the adjustment of several empirical expressions that reduce the computational time to simulate the yield and ultimate behaviour of a given reinforced concrete rectangular section under either monotonic or cyclic loading. The expressions are calibrated with a selection of tests, from a published database of more than 1000 tests, under the criterion that the selected specimens comply with the seismic construction requirements of the main international building codes (EC‐2, EC‐8 and ACI‐318). Due to their robustness and acceptable computation time for low‐dimensional problems, genetic algorithms are used for this calibration. The equations proposed can be employed by structural engineers for the design and analysis of actual structural elements used in ordinary reinforced concrete buildings located in seismic areas, providing more accurate results than other expressions.
      PubDate: 2016-02-18T08:57:07.971531-05:
      DOI: 10.1002/suco.201500107
       
  • DESIGN RECOMMENDATIONS FOR REINFORCED CONCRETE INTERFACES BASED ON
           STATISTICAL AND PROBABILISTIC METHODS
    • Abstract: A concrete interface is a material discontinuity which requires special care in structural design and assessment. Therefore, the definition of design expressions, based on experimental testing data, must ensure the needed reliability depending on the type of structure and its use. In the present work, a new proposal for the design of concrete interfaces subjected to shear loading is presented for different roughness profile types. The proposal is characterized by 3 linear branches (for monotonic loading), an S‐N curve (for cyclic loading) and is the result of a parametric analysis of existing experimental data (obtained by the authors and also from an extensive literature search) based on statistical and probabilistic methods. Design expressions were defined in order to minimize dispersion and variability of the safety factor values for each considered experimental test, and also to assure that those values are within a target range (defined according to reliability considerations). These improvements became clearer when the new proposal was compared with the most common design code recommendations.
      PubDate: 2016-02-18T08:55:53.312573-05:
      DOI: 10.1002/suco.201500083
       
  • Real‐time damage detection based on pattern recognition
    • Abstract: Structural Health Monitoring (SHM) can be defined as the process of developing and implementing structural damage detection strategies. Ideally, this detection should be carried out in real time before damage reaches a critical state and impairs structural performance and safety. Hence, it must be based on sensorial systems permanently installed on the target structures and on fully automatic detection methodologies. The ability to detect damage in real‐time is most important for controlling the safety of aged structures or for post‐retrofitting / post‐accident situations, where it might even be mandatory for ensuring a safe service. Under these constraints, SHM systems and strategies must be capable of conducting baseline‐free damage identification, i.e., they must not rely on comparing newly acquired data with baseline references in which structures must be assumed as undamaged. The present paper describes an original strategy for baseline‐free damage detection based on the application of artificial neural networks and clustering methods, in a moving windows process. The proposed strategy was tested and validated on numerical and experimental data obtained from a concrete cable stayed bridge and proved effective in automatically detecting small stiffness reductions in single stay cables as well as the detachment of neoprene pads in anchoring devices, resorting only to a small amount of inexpensive sensors.
      PubDate: 2016-02-18T08:55:40.412952-05:
      DOI: 10.1002/suco.201500092
       
  • The structural redistribution coefficient KRd: A numerical approach to its
           evaluation
    • Authors: Marco di Prisco; Paolo Martinelli, Daniele Dozio
      Abstract: Structures made of a material with a very high standard deviation, such as fibre‐reinforced concrete, show a too safe prediction of the maximum bearing capacity when derived from characteristic values identified by means of small specimens. This is emphasized when the structures are characterized by a large redundancy. In this regard, two reference tests representing two extreme situations are considered: (a) simply supported unnotched full‐scale beams characterized by a statically determinate loading scheme and (b) full‐scale slabs on the ground characterized by a statically indeterminate loading scheme. The Italian Standard and more recently Model Code 2010 have introduced a coefficient (structural redistribution factor) that is able to take into account the reduced variability of the mechanical strength when associated with a large volume involved in the failure process or when the structure is able to significantly redistribute stresses, favouring the average strength rather than the minimum one. A numerical procedure taking into account the expected heterogeneity of the mechanical characteristics in the structure is introduced for the first time to evaluate the redistribution factor.
      PubDate: 2016-02-18T08:55:26.599252-05:
      DOI: 10.1002/suco.201500118
       
  • PUNCHING SHEAR TESTS ON COMPACT FOOTINGS WITH UNIFORM SOIL PRESSURE
    • Abstract: Punching shear is usually the governing failure criterion for the selection of the depth of reinforced concrete footings. Despite the fact that large experimental programmes have been performed in the past aimed at the punching strength of slender flat slabs, only a few experimental campaigns on full‐scale compact reinforced concrete footings can be found in the literature. In this paper, the results of an experimental programme including 8 reinforced concrete footings with a nominal thickness of 550 mm is presented. These experiments investigated the influence of the column size, member slenderness and the presence of compression and shear reinforcement. The tests were performed using an innovative test setup to ensure a uniform soil pressure. The experimental results show that the slenderness influences the punching shear strength as well as the effectiveness of the shear reinforcement. It is also experimentally shown that an important interaction amongst bending and shear occurs for high levels of shear forces near the column (typical case of compact footings or members with large amounts of shear reinforcement). Different continuous measurements recorded during the experimental tests allow a complete description of the kinematics and strains at failure. On that basis, experimental evidence is obtained showing that crushing of the concrete struts near the column is the phenomenon that triggers the punching failure of compact footings.
      PubDate: 2016-02-18T08:55:14.661851-05:
      DOI: 10.1002/suco.201500175
       
  • Fatigue behaviour of a normal‐strength concrete – number of
           cycles to failure and strain development
    • Abstract: The fatigue behaviour of concrete is gaining new relevance against the backdrop of continuous development in concrete construction. Modern types of concrete achieving ever higher strengths; hence concrete constructions are becoming increasingly attractive for new fields of application such as onshore and offshore wind turbines. The fatigue of concrete has a special relevance for these cyclic‐loaded constructions. Knowledge of the number of cycles to failure is no longer sufficient for the design of these kinds of constructions. There are further questions concerning strain and stiffness development and the combination of fatigue loading and maritime environmental conditions which have been investigated with new testing methods at Leibniz Universität Hannover within the research project “ProBeton”. The first results of this research project, which is supported by the Federal Ministry for Economic Affairs and Energy, are presented here.
      PubDate: 2016-02-18T08:54:59.611208-05:
      DOI: 10.1002/suco.201500139
       
  • Modification of the simplified method of crack control included in EN
           1992–3
    • Authors: Mariusz Zych
      Abstract: The methods of liquid retaining RC tank walls crack control are analysed taking into account external load (EN 1992‐1‐1) and imposed strain occurring at the elevation stage (EN 1992‐3), i.e. during concrete hardening period. The convergence ranges of the simplified method of crack control included in EN 1992‐3 and the detailed calculation methods included in EN 1992‐1‐1 and EN 1992‐3 are defined. Apart from the compatibility areas, overestimation of the acceptable reinforcement bar diameter φs⋆ displayed in Fig. 7.103N in EN 1992‐3 was proved. Coefficients κφ1 and κφ2 are defined, which enabled a calculation of the acceptable reinforcement bar diameter φs⋆ in order to obtain the values complying with the direct calculations. For practical purposes, graphs were plotted, which facilitates the definition of coefficients κφ1 and κφ2 without performing direct calculation. On the basis of the analyses performed and the relations proposed it can be concluded that there is a possibility or a necessity to increase or decrease the acceptable reinforcement bar diameter φs⋆, depending on the concrete mechanical properties and geometrical properties of a RC tank wall.
      PubDate: 2016-02-18T08:50:40.451423-05:
      DOI: 10.1002/suco.201500077
       
  • Experimental Evaluation of Optimized Strut‐and‐Tie Models for
           a Dapped Beam
    • Abstract: Strut‐and‐Tie modeling provides a powerful tool for the design of complex structural reinforced concrete elements. It has been proved numerically that strut‐and‐tie models obtained with the application of structural optimization methods produce designs that are more efficient. However, to the best of the authors' knowledge, no experimental evidence of such results has been published. This paper presents experimental results for nine test specimens: five of them are designed using optimal models derived from a Full Homogenization structural optimization algorithm, and the remaining four are designed using conventional strut‐and‐tie models, for comparison purposes. While all specimens carry loads higher than the factored design load, specimens based on ST models derived using Full Homogenization with reinforcement parallel to the ties, exhibit better structural performance, regarding crack growth control, more ductile modes of failure, and larger increase in load capacity.
      PubDate: 2016-02-18T08:50:28.588161-05:
      DOI: 10.1002/suco.201500037
       
  • AN IMPROVEMENT OF THE EUROCODE 2 AND fib MODEL CODE 2010 METHODS FOR THE
           CALCULATION OF CRACK WIDTH IN R.C. STRUCTURES
    • Authors: Pier Giorgio Debernardi; Maurizio Taliano
      Abstract: The analysis of the mechanical behaviour of a reinforced concrete tie subjected to a monotonic loading, in the stabilized cracking stage, is here performed through a theoretical general model that considers the effect of the so‐called Goto cracks or secondary cracks. It is shown, in particular, that the average bond stress along the transmission length depends not only on the concrete strength as assumed by fib Model Code 2010, but also on the reinforcement ratio and bar diameter. To this regard, tabulated theoretical values of the average bond stress are proposed as a function of the aforementioned parameters. Moreover, the secondary cracks reduce the effect of tension‐stiffening on the relative mean strain. On the basis of the main results obtained with the general model some improvements to the calculation methods proposed by fib Model Code 2010 and Eurocode 2, concerning the average value of the bond stress and taking account of the influence of the secondary cracks on the mean deformation, are suggested. An improved calculation method is therefore performed. Finally, the theoretical results of crack spacing and crack width obtained with the general and improved methods are compared to the experimental data obtained from an extensive research on r.c. ties.
      PubDate: 2016-02-09T06:28:51.638222-05:
      DOI: 10.1002/suco.201500033
       
  • High cycle fatigue behaviour of reinforcing steel under the effect of
           ongoing corrosion
    • Authors: Christoph Gehlen; Kai Osterminski, Tim Weirich
      Abstract: This paper presents results on the corrosion fatigue behaviour of profiled reinforcing steel bars. Cyclic loaded rebar was simultaneously exposed to different corrosive environments – moderate up to severe corrosive environments simulating XC or XD/XS exposure. Corrosion was naturally configured without any external polarization. Rebar was either directly exposed to the corrosive solutions or, when embedded in concrete, indirectly. In this case corrosive agents penetrated through an open crack towards the steel surface. Low frequency was applied to enable extended corrosion periods. In order to detect and quantify the crack initiation and crack growth of the rebar, the potential drop method was utilized. Based on this method, ratios of the number of cycles to initiate a crack to cycles to failure could be determined. Based on this method, the Nini/NF‐ratios were almost always between 0.8 and 0.9 ‐ values which are similar to ratios determined for air tested rebar (reference). This indicates that the fatigue life of rebar in carbonated or chloride containing concrete is strongly related to the crack initiation and less on the crack growth. The S‐N curves derived from the corrosion fatigue tests deviate significantly from the curve that was measured from the reference fatigue tests (tests in air). The S‐N curves of rebar tested under corrosion fatigue load were linear with a slope which was much steeper than the slope of the of the reference rebar tested in air.
      PubDate: 2016-02-09T06:28:39.736187-05:
      DOI: 10.1002/suco.201500094
       
  • DUAL POTENTIAL CAPACITY MODEL FOR REINFORCED CONCRETE BEAMS SUBJECTED TO
           SHEAR
    • Authors: Deuck Hang Lee; Sun-Jin Han, Kang Su Kim
      Abstract: The shear resistance mechanisms of a reinforced concrete (RC) member with shear reinforcement can be divided into the contributions of concrete and shear reinforcement. The shear resistance mechanisms of concrete can be further divided into the shear resistance of intact concrete in the compression zone, the aggregate interlock in the cracked tension zone, and the dowel action of the longitudinal tension reinforcement. In this study, the shear demand curves and potential shear capacity curves for both tension and compression zones were derived with the assumption that the shear failures of RC members are dominated by the flexural‐shear strength. On this basis, the shear capacity model was also proposed. In the proposed model, the crack width and the local stress increase in reinforcements were calculated based on the bond behavior between the reinforcement and its surrounding concrete, and the crack concentration factor was introduced to consider the formation and propagation of the critical shear crack developed from the flexural cracks. A total of 940 shear test results was collected and compared with the analysis results provided by the proposed model, and it was demonstrated that the proposed model provided a good estimation on the shear strengths of RC beams.
      PubDate: 2016-02-09T06:28:02.131008-05:
      DOI: 10.1002/suco.201500165
       
  • Axial Loading Capacity of Concrete‐Jacketed RC Columns with
           Pre‐ and Post‐Corrosion Damage
    • Authors: Yuxi Zhao; Dawei Zhang, Shijun Shen, Tamon Ueda
      Abstract: The main objective of this study is to investigate the effect of pre‐ and post‐jacketing corrosion and loading damage on concrete‐jacketed reinforced concrete (RC) columns under uni‐axial loading and to develop a methodology for predicting the corresponding compressive strength. The pre‐ and post‐damage involved a pre‐loading up to 50% of the peak load of core column, an electrochemical process to accelerate the migration of chlorides from an external electrolyte into the tested columns and a wetting‐drying cycle process with a controlled current to speed up the corrosion of the reinforcing steel bars in the tested columns. Uni‐axial loading tests were performed to determine the structural performance of the concrete‐jacketed columns with and without corrosion damage. The failure mode, load displacement and load strain responses of the test columns were recorded, and the related mechanisms are discussed. A model capable of evaluating the compressive strength of un‐jacketed or jacketed RC columns with and without corrosion damage was then developed. The analytical approach considered the effect of reinforcement corrosion on the effective load‐bearing area of the concrete and the confinement effect from the stirrups. The analytical results agreed well with the experimental results, indicating the reliability and effectiveness of the developed models.
      PubDate: 2016-02-09T06:24:48.598334-05:
      DOI: 10.1002/suco.201400113
       
  • Structural Performance of Continuous R.C. Slabs Strengthened in Negative
           Moment Region using Mineral Based Composite
    • Authors: Ahmad Atta; Fahmy Zaher, Emad Etman
      Abstract: An experimental program was proposed and carried out to assess the effectiveness of the Mineral Based Composite (MBC) technique for the flexural strengthening of a negative moment in continuous reinforced concrete slabs. In addition to the testing of the two control specimens, the experimental program included the testing of nine continuous RC slab specimens with different details of the strengthening techniques, namely, using ordinary steel bars, and Mineral Base Composite (MBC) material. This experimental program was conducted to study the modes of failure, the load‐deflection behavior, and the failure loads. Furthermore, we present and describe a comparative study between the two strengthening techniques, namely, reinforced steel bars with Mineral Based Composite (MBC) or steel bars with epoxy mortar. Based on the presented experimental results, both strengthening techniques of the continuous slabs are evidently efficient. In this study, the measured results for the average cracks spacing were compared with the limits stipulated in CEB‐FIP code 1990 and the failure load calculations were extended with an analytical approach based on the ultimate theory for the failure load calculation. In conclusion, the results obtained from the analytical model are in agreement with the experimental results.
      PubDate: 2016-02-01T05:40:10.001804-05:
      DOI: 10.1002/suco.201500026
       
  • Numerical limit analysis of keyed shear joints in concrete structures
    • Authors: Morten A. Herfelt; Peter N. Poulsen, Linh C. Hoang, Jesper F. Jensen
      Abstract: This paper concerns the shear capacity of keyed joints, which are transversely reinforced with overlapping U‐bar loops. It is known from experimental studies that the discontinuity of the transverse reinforcement affects the capacity as well as the failure mode; however, to the best knowledge of the authors, previous theoretical works and present design equations in standards do not account for this important effect. In this paper, a detailed model based on finite element limit analysis is introduced to assess the effect of the discontinuous reinforcement. The model is based on the lower bound theorem and uses the modified Mohr‐Coulomb yield criterion, which is formulated for second‐order cone programming. The model provides a statically admissible stress field as well as the failure mode. Twenty‐four different test specimens are modelled and the calculations are compared to the experimental results. The results of the model show satisfactory agreement with the experimental observations. The model produces significantly better estimates of the shear capacity than the design equations of Eurocode 2.
      PubDate: 2016-02-01T05:39:54.825221-05:
      DOI: 10.1002/suco.201500161
       
  • Accuracy of design‐oriented formulations for the evaluation of
           flexural and shear capacities of FRP strengthened RC beams
    • Abstract: Fiber reinforced polymer (FRP) composites have been largely employed in the last few decades for strengthening and retrofitting existing reinforced concrete (RC) structures. Several studies are available in the literature and different analytical models were proposed for the evaluation of the FRP contribution in strengthened RC elements. This paper analyzes the accuracy of widely used analytical models, some of which are included in design guidelines, for the evaluation of flexural and shear contributions provided by the FRP. In particular, the analytical models for the evaluation of the FRP strain at intermediate crack‐induced debonding failure are analyzed. The accuracy of each formulation is assessed comparing the analytical provisions with the experimental results collected from two databases, one for bending and one for shear. The results obtained showed that most of the analytical flexural models attained a good level of accuracy and only few models provide inadequate results. A new formulation proposed for the evaluation of the FRP shear contribution is shown to be generally conservative, which comes at the expense of accuracy.
      PubDate: 2016-02-01T05:39:42.934696-05:
      DOI: 10.1002/suco.201500066
       
  • Punching shear strength of flat slabs: Critical review of Eurocode 2 and
           fib Model Code 2010 design provisions
    • Authors: Marcus Ricker; Carsten Siburg
      Abstract: fib Model Code 2010 introduces a new design concept for punching shear, which is based on the Critical Shear Crack Theory. In this paper, the design provisions for punching shear according to fib Model Code 2010, Eurocode 2 and the corresponding German National Annex to Eurocode 2 are presented and background information is given. By means of parameter studies and a comparison of the calculated resistances and test results, the different punching shear design provisions are critically reviewed. The safety levels of the code provisions are verified and the influence of the different punching parameters on the calculated resistances is examined in detail.
      PubDate: 2016-02-01T05:39:28.80501-05:0
      DOI: 10.1002/suco.201500106
       
  • Mechanics closed form solutions for moment redistribution of RC beams
    • Authors: Phillip Visintin; Deric J. Oehlers
      Abstract: For the efficient design of reinforced concrete beams and frames, moment redistribution is used to: reduce the absolute maximum magnitude of the moment in the critical region; equalise the critical moments at either side of interior columns and fully utilise the capacity of the non‐critical regions of a member. Although important, moment redistribution has historically proved to be difficult to quantify due to the complexity of quantifying hinge rotations. Although numerous empirical expressions exist for plastic hinge lengths, that is, the length over which the ultimate curvature can be integrated in order to give hinge rotations, a comparison with a global data set yields poor results. Using a recently developed mechancis based moment rotation approach it is possible to quantify the moment rotation characteristics of reinforced concrete hinges. In the tension region, the approach directly applies partial interaction theory to simulate the mechanisms associated with slip of the reinforcement relative to the surrounding concrete as cracks widen. While in the compression region, partial interaction shear friction theory is used to describe the formation and failure of concrete softening wedges. It is shown how the moment rotation approach explicitly allows for the size dependency. Furthermore, mechanics based solutions for moment redistribution are then derived and it is shown how these can be simplified at the ultimate limit state for use in the design office.
      PubDate: 2016-02-01T05:39:16.314284-05:
      DOI: 10.1002/suco.201500085
       
  • Investigation of the buckling behavior of thin‐walled concrete
           hollow piers
    • Abstract: Hollow tall concrete piers with high width‐to‐thickness ratios are commonly used in long‐span box girder bridges. Such thin‐walled structures present the possibility of failure due to local buckling. So, in common practice, diaphragms are usually set in hollow piers to improve the local stability, however, is it necessary? Although experimental research on the buckling behavior of hollow piers had been conducted extensively, only little analytical attempts have been made to reveal the effects of width‐to‐thickness ratio on local buckling behavior. To this end, an analytical model has been proposed to investigate the local buckling behavior of hollow piers. Following the Ritz‐Timoshenko methods, an analytical formula for critical local buckling stress is developed and verified to have good accuracy compared with finite element analyses. Based on the buckling failure mode of the hollow pier with the slenderness ratio over 6, it can be reasonably postulated that the strength of the hollow pier will be unaffected by local compression flange buckling when the wall width‐to‐thickness ratio is less than 24, and it is entirely unnecessary to set diaphragms in hollow piers in the view of stability. Additionally, it is equally interesting that the critical width‐to‐thickness ratio of the hollow pier with the slenderness ratio over 4 derived by the proposed model is the same as the value given by the current AASHTO‐LRFD Bridge Design Specifications.
      PubDate: 2016-01-22T03:10:07.982898-05:
      DOI: 10.1002/suco.201500043
       
  • Predicting the behaviour of concrete structures – modelling or
           testing?
    • Authors: Hans Beushausen
      Pages: 1 - 2
      PubDate: 2016-03-09T11:38:17.435264-05:
      DOI: 10.1002/suco.201670016
       
  • fib‐news: Structural Concrete 1/2016
    • Pages: 125 - 131
      Abstract: Contents Issue 1 (2016) fib MC2020: The story so far New fib SG fib‐ACI MoC Betontage in Shanghai COM4: Materials‐related priorities 4th IWCS Ralejs Tepfers 1933‐2015 Gabriel Tevec 1936‐2016 Congresses and symposia Acknowledgement
      PubDate: 2016-03-09T11:38:15.408841-05:
      DOI: 10.1002/suco.201670012
       
  • Structural Concrete 2/2016
    • Pages: 132 - 132
      PubDate: 2016-03-09T11:38:14.880782-05:
      DOI: 10.1002/suco.201670013
       
  • Estimating loads on shores during the construction of RC building
           structures
    • Abstract: When constructing reinforced concrete (RC) building structures, knowing the loads to which the shoring system will be subjected during the entire process is one of the key aspects to ensure safety during the work. Although various simplified methods of estimating the load transmission between shores and slabs during construction have been proposed to date, none of these methods can estimate the loads on individual shores during the different construction phases. This paper proposes a calculation method that allows the loads on individual shores to be calculated for each construction phase, without having to resort to the use of advanced software. The proposal was validated by comparison with the results obtained from two actual buildings under construction and represents a step forward in the construction of RC building structures, as it is the first method that offers the possibility of estimating the loads acting on each shore during all the construction phases.
      PubDate: 2015-12-14T03:50:37.79987-05:0
      DOI: 10.1002/suco.201500130
       
  • Unified cyclic stress‐strain model for FRP‐confined concrete
           circular, square and rectangular prisms
    • Authors: Hadi Ziaadiny; Reza Abbasnia
      Abstract: Behavior and modeling of concrete columns confined with FRP composites under monotonic compression has been extensively studied, but cyclic behavior of FRP‐confined circular and rectangular columns has much less been investigated. A reliable model indicating the cyclic stress‐strain behavior of FRP‐confined columns is of great importance especially for seismic retrofit and design of these columns. In this paper, based on the results from a series of cyclic compressive loading tests of FRP‐confined specimens, a unified cyclic stress‐strain model is proposed for circular, square and rectangular columns confined with FRP composites. The model contains different parts of cyclic stress‐strain curve, including plastic strain, maximum strain of unloading path and corresponding stress, stress deterioration, effect of loading history, partial unloading and partial reloading. New expressions are also proposed for predicting unloading and reloading paths. The proposed model provides good agreement with the test results.
      PubDate: 2015-12-11T06:40:09.127092-05:
      DOI: 10.1002/suco.201500128
       
  • Background to European seismic design provisions for the retrofit of R.C.
           elements using FRP materials
    • Authors: S.J. Pantazopoulou; S.P. Tastani, G.E. Thermou, T. Triantafillou, G. Monti, D. Bournas, M. Guadagnini
      Abstract: This paper is a comprehensive state of the art background document on European seismic design provisions which was assembled in support of the development of design guidelines by the fib Committee 5.1 regarding the use of externally applied Fiber Reinforced Polymers (FRP) materials in the seismic retrofitting of reinforced concrete structures. In the context of developing design guidelines, the underlying mechanistic models that support the derivation of provisions were assembled after critical evaluation of the existing proposals and with careful reference to the available experimental evidence, the comparative assessment of past models in the literature, and requirements established from first principles.
      PubDate: 2015-12-11T06:40:08.17766-05:0
      DOI: 10.1002/suco.201500102
       
  • Modeling Catenary Effect in Progressive Collapse Analysis of Concrete
           Structures
    • Authors: Arash Naji
      Abstract: Progressive collapse is a phenomenon in which local failure of a structural component due to gas explosion or blast may leads to failure of the entire structure or significant part of it. RC structures can resist progressive collapse through various mechanisms like frame action and catenary action. In this paper, using Limit Analysis, the effect of catenary action on resistance of concrete frame structures against progressive collapse is modeled. In this regard, nonlinear optimization is performed. It is observed that although frame action is known as the main mechanism that resist progressive collapse, but at the end of this action, after rupture of bottom bars, catenary effects may have noticeable increase on resistance of the structure. The results have good agreement with experimental results done by other researchers.
      PubDate: 2015-11-13T02:20:15.073582-05:
      DOI: 10.1002/suco.201500065
       
  • Time‐variant reliability analysis of RC bridge girders subjected to
           corrosion – shear limit state
    • Authors: P.V. Ahsana; K. Balaji Rao, M.B. Anoop
      Abstract: Chloride induced corrosion of reinforced concrete (RC) bridge girders has led to huge loss of national resources. One of the important concerns of RC bridge girders is corrosion of stirrups, because of which, failure mechanism can even change from a ductile flexural mode to a brittle shear mode. Hence, analysis of reduction of shear capacity with time is essential in their reliability assessment, which is the topic of the paper. This paper proposes a stochastic modeling approach for estimation of time‐variant shear capacity and reliability within the framework of Monte Carlo simulation, which assists in sustainability‐based service‐life design of bridge girders. Such modern concepts of design require methodologies for estimating whole life cost at the design stage itself. Development of such methodologies would provide the designer various options to arrive at optimum design having desired performance level during the service life. The proposed approach takes into account:1) randomness in basic variables, 2) effect of micro‐environment and spatial variation of corrosion, 3) number of stirrups resisting web shear failure, and 4) ductile to brittle transition of stirrup steel with corrosion propagation. Incorporation of this transition is found to have significant influence in the time‐variant reliability of the girder. Though PFA concrete is known to have better durability characteristics than OPC concrete, this paper gives a framework for its quantification in terms of time variant reliability.
      PubDate: 2015-11-13T02:20:13.896505-05:
      DOI: 10.1002/suco.201500081
       
  • Investigation of optimal layout of ties in STM developed by topology
           optimization
    • Abstract: Strut‐and‐tie models (STMs) have been wildly used for the design of disturbed regions in structural concrete members. The STM developed based load path method or with the aid of stress trajectories is not unique and varies with the designer's intuition and past experience. As a result, topology optimization methods have been adopted to generate STMs in reinforced concrete structures. However, such models are just a preliminary configuration, and the detailed layout of ties in STM can not be determined by the optimal topology. This is because the reinforced concrete is assumed to be a uniform elastic continuum. Therefore, the effect of the steel reinforcement on the load transmission can not be considered in the optimization process. Recently, the criterion of minimum strain energy has been proposed to determine the optimal layout of STM obtained by the modified optimization method. However, such strain energy criterion does not work when the minimum strain energy in ties is zero evaluated by mathematical equations. To address this issue, the maximum stiffness criterion is proposed to find out the optimal layout of ties in STM by evaluating the stiffness of strut ties.
      PubDate: 2015-11-13T02:20:12.865972-05:
      DOI: 10.1002/suco.201500093
       
  • A New Approach for the Calculation of Internal Forces, Moments and
           Deflections of Sandwich Panels with Reinforced Concrete Facings
    • Abstract: As part of a research project at the Technische Universität Kaiserslautern, software for the calculation of internal forces, moments and deflections of sandwich elements with reinforced concrete facings has been developed. Sandwich elements with stiff concrete facings are internally statically indeterminate. The cracking of the concrete facings leads to a redistribution of internal forces and moments over the length and across the cross‐section of the element. This redistribution must be considered in the structural design of these elements. An existing program for the calculation of metal‐faced sandwich elements was considerably extended by an iterative approach, which allows the calculation of the internal forces and moments with the accurate stiffness of the cracked facings. In the following paper, this iterative approach as well as the calculation algorithm behind the new software, called swe2+, are explained. Furthermore, a verification of the calculation results and a parametric study on a two‐span sandwich element are presented.
      PubDate: 2015-11-13T02:20:11.78297-05:0
      DOI: 10.1002/suco.201500104
       
  • Properties of stabilized recycled plastic concretes made with three types
           of cements
    • Authors: Faiz Uddin Ahmed Shaikh; Sarvesh Mali
      Abstract: The growing concern for ready mix concrete industry is the disposal of returned unused concrete. In a plastic state, the concrete is a perishable product and the disposal of any unused concrete provides a set of challenges. An increase in environmental regulations requires the industry to implement the best practices that effectively reduces the quantity of by‐product materials require disposal. This paper reports a preliminary experimental study on the effect of commercial stabilizer on the plastic and harden properties of concretes made with three different types of cements commonly used in Australia, namely general purpose Portland cement (GP) (100% ordinary Portland cement (OPC)), general purpose blended (GB) cement (75% OPC + 25% Class F fly ash (FA)) and low heat (LH) cement (35% OPC + 65% blast furnace slag). In the initial phase, the effect of various stabilizer dosages on the efflux time (flow time) of GP, GB and LH cements grouts is studied. The results showed that for a constant efflux time the holding duration of the grouts increases with increasing stabilizer dosages (or amounts) and in the case of GB and LH cements grouts the holding duration is longer than the GP cement grout for the same stabilizer dosage. In the next phase, the predicted stabilizer dosage was added in concretes made with above three cements to evaluate the plastic and harden properties of fresh concretes, stabilized concretes and blend of fresh concretes with 10%, 25% and 50% stabilized concretes. Results show that, the initial slump values are within the tolerance except it is higher when stabilizer dosage is added after an hour, but the final slump is within the tolerance of control concrete. After stabilization of the concretes, the initial and final setting time of stabilized concretes is increased to more than 24 hours. The initial and final setting time of the blended concrete containing fresh concrete and 10%, 25% and 50% stabilized concretes are similar to those of fresh concrete for all cements types. The stabilized concretes do not have any significant effect on compressive strength and shrinkage compared to the control concrete.
      PubDate: 2015-11-13T02:20:10.44568-05:0
      DOI: 10.1002/suco.201500111
       
  • Influence of reinforcement bar layout on fibre orientation and
           distribution in slabs cast from fibre‐reinforced
           self‐compacting concrete (FRSCC)
    • Abstract: Fibre orientation and volume distribution affect the post‐cracking tensile strength, which is one of the main design parameters of fibre‐reinforced concrete (FRC). This paper discusses the influence of unidirectional and grid reinforcement on fibre orientation and distribution in FRC slabs. Slabs without conventional reinforcement bars were used as reference. The slab size was 1200x1200x150mm3. Numerical simulations were used to predict the fibre orientation. To determine the actual fibre orientation and distribution, X‐ray Computed Tomography (CT) was used. Beams were sawn from each slab, CT‐scanned, and tested in three‐point bending tests in accordance with EN 14651. Both the numerical simulations and the CT results show that the rebars caused a more isotropic fibre orientation in the lower halves of the slabs. This was confirmed in the bending tests, where the lowest variation and highest residual tensile strengths were documented for beams sawn from grid‐reinforced slabs. Fibre migration from the upper layer to middle and lower layers of the slabs due to gravity was observed in all slabs, and in the reinforced slabs migration also depended on the distance from the casting point. The reinforcement led to an accumulation of fibres above the rebars in the middle layer of the reinforced slabs. A set of mechanisms is proposed to explain the experimental results.
      PubDate: 2015-11-13T02:10:08.905309-05:
      DOI: 10.1002/suco.201500064
       
  • Experimental Study on Fatigue Behavior of CFRP Plates Externally Bonded to
           Concrete Substrate
    • Authors: Wei Zhang
      Abstract: The behavior of the bond between fiber‐reinforced polymer (FRP) and concrete greatly influences the behavior of concrete structures strengthened with FRP composites. Although numerous experimental studies have investigated this bond, experimental data concerning fatigue tests on carbon FRP plates applied to concrete blocks are still lacking. Thus, a series of double‐lap shear tests under monotonic and fatigue loadings were performed on concrete prismatic specimens reinforced with CFRP plates. First, a series of experimental investigations are summarized. Thereafter, the fatigue behavior of CFRP plate debonding is characterized using S–N diagrams, which represent the relationship of the upper‐limit fatigue load with the monotonic load strength and the number of cycles to debonding on a semi‐logarithmic scale.
      PubDate: 2015-11-13T02:10:07.746729-05:
      DOI: 10.1002/suco.201500044
       
  • Probabilistic Degradation Modeling of Segmental Linings Assembled Circular
           Tunnels
    • Authors: Qing Ai; Yong Yuan, Sankaran Mahadevan, Xiaomo Jiang
      Abstract: Cross‐section deformation is considered an important indicator for assessing the structural safety in inspection and maintenance of tunnels. Its increase during lifetime is an indication of the gradual degradation of structural performance. In order to take timely and appropriate maintenance measures before the tunnel reaches the ultimate limit state, a predictive degradation model of cross‐section deformation should be established. In this paper, a probabilistic degradation model is developed based on an average uniform rigidity ring model for segmental linings assembled circular tunnels. By considering the uncertainties and relevant time‐varying performances of parameters the model is able to give probabilistic and time‐dependent predictions. Critical parameters are identified and the model is simplified after sensitivity analysis. Based on the measuring data, a Bayesian updating method is proposed to improve the input assumptions and predictions of the model. This research provides a perspective on the degradation modelling of the cross‐section deformation of segmental linings assembled circular tunnels and methods for improving the proposed predictive model.
      PubDate: 2015-11-13T02:10:07.541513-05:
      DOI: 10.1002/suco.201400122
       
  • European Design Rules for Point Load Near Support evaluated with Data from
           Shear Tests on Non‐Slender Beams with Vertical Stirrups
    • Abstract: This paper includes a presentation of a shear test database that contains 278 tests conducted on reinforced concrete beams with vertical stirrups and without horizontal skin reinforcement. These beams are commonly referred to as non‐slender beams since they were tested by using loading arrangements that created shear span‐to‐depth ratios (a/d) less than 2.4. In an effort to arrive at a database that can be used for the purposes of evaluating the accuracy and conservativeness of design provisions, several control and filtering criteria were applied. After this process 178 beams remained in the evaluation database. The analyses conducted by using this database indicated that the application of strut‐and‐tie models (STM) of Eurocode 2 (EC2) to non‐slender beams with stirrups was unconservative, i.e. the database analyses yielded results that were above the desired 5%‐fractile. Almost all unconservative strength estimations were obtained for test specimens containing large quantities of stirrups. Conversely, statistical evaluations showed that FIP Recommendations model for beams with point loads near the support were conservative.
      PubDate: 2015-10-12T04:21:16.797618-05:
      DOI: 10.1002/suco.201500089
       
  • Evaluation of safety formats for non‐linear Finite Element Analyses
           of statically indeterminate concrete structures subjected to different
           load paths
    • Authors: Mattias Blomfors; Morten Engen, Mario Plos
      Abstract: To increase the efficiency of new structures and to perform safety evaluations of existing structures the nonlinear behavior of reinforced concrete should be modelled and analyzed. The applicability of the safety formats in present design codes to indeterminate structures subjected to loading in several directions is unclear. The safety formats in Model Code 2010 have been evaluated for a reinforced concrete frame subjected to vertical and horizontal loading and the influence of load history was studied. Basic reliability methods were used together with response surfaces to assess the failure probabilities and all safety formats did not meet the intended safety level. The results indicate the importance of load history and it is concluded that more research regarding how it influences the safety level of complex structures is required.
      PubDate: 2015-09-23T03:30:09.452015-05:
      DOI: 10.1002/suco.201500059
       
  • Anchorage of composite dowels in UHPC under fatigue loading
    • Authors: Joerg Gallwoszus; Alexander Stark, Martin Classen
      Abstract: In steel‐concrete composite structures, innovative composite dowels can be used for the connection of ultra‐high performance concrete (UHPC) slabs and high‐strength steel members. In addition to sufficient shear capacity, composite dowels have to ensure the transmission of tensile forces in the composite connection in order to prevent lifting of the concrete slab. This may lead to structural problems, particularly in the very slender concrete slabs of high‐strength composite beams, where composite dowels have very small embedment depths. Although there already exist findings concerning the structural anchorage behavior of composite dowels under static loads, studies on the fatigue of composite dowels under cyclic pull out loading are still lacking, so far. As the fatigue behavior in crucial for applications in bridge construction, the present paper introduces cyclic pull out tests of composite dowels in UHPC slabs. Here, the influence of different load‐dependent parameters (upper load level and load range) as well as the use of a transverse reinforcement has been investigated. Furthermore, an approach to assess the lifetime of composite dowels in UHPC under cyclic pull out loading is proposed.
      PubDate: 2015-09-03T03:41:58.79363-05:0
      DOI: 10.1002/suco.201500034
       
  • Mechanical, durability and hygrothermal properties of concrete produced
           using Portland cement‐ceramic powder blends
    • Abstract: Blended Portland cement‐ceramic powder binder containing up to 60% of fine‐ground waste ceramics from a brick factory is used in concrete mix design, as an environmental‐friendly alternative to the commonly used Portland cement. The experimental analysis of basic physical characteristics, mechanical and fracture‐mechanical properties, durability properties and hygrothermal characteristics shows that the optimal amount of ceramic powder in the mix is 20% of the mass of blended cement. The decisive parameters in that respect are the compressive strength, liquid water transport parameters and resistance against deicing salts which are not satisfactory for higher ceramics dosage in the blends. In the case of other studied parameters, the limits for the effective use of ceramic powder are higher, 40% for the effective fracture toughness and specific fracture energy, 60% for the frost resistance and chemical resistance to MgCl2, NH4Cl, Na2SO4, HCl and CO2. The water vapor diffusion coefficient is found to increase with the increasing content of ceramics which for wet envelopes can be considered as a positive feature but for dry envelopes it may have a negative effect. The thermal conductivity of all mixes increases fast with growing moisture content; up to 50% differences between the dry‐ and water saturated state values are observed. This has to be taken into account in energy‐related calculations.
      PubDate: 2015-08-07T02:10:07.454623-05:
      DOI: 10.1002/suco.201500029
       
  • A New Method for Proportioning Recycled Concrete
    • Authors: Pramod K. Gupta; Ziyad A. Khaudhair , Ashok K. Ahuja
      Abstract: In this paper, a new modified mix proportioning method named as Equivalent Coarse Aggregate Mass (ECAM) to produce normal strength concrete using recycled concrete aggregate is proposed. Basic concepts of the proposed method with calculations for mix design are presented through designing fourteen mixes and testing of 99 concrete samples including 57 cubes and 42 cylinders. Experimental work was carried out in two phases. In the first phase, an experimental program was carried out to verify the proposed mix design method by studying a single parameter uniaxial compressive strength. Five different mixes with initial 0%, 25%, 50%, 75% and 100% replacements by mass were designed, casted and tested in this phase. It was concluded from the first phase that the proposed method can be adopted for designing the recycled concrete up to a nominal replacement ratio of 50%. Accordingly, the second phase of experimental study was conducted to design three different grades of concrete strength using the proposed method to investigate the mechanical properties of the recycled concrete. Seven different mechanical properties which include compressive strength, splitting tensile strength, modulus of elasticity, Schmidt Hammer test, ultrasonic pulse velocity test, fresh density and hardened density were investigated, presented and discussed.
      PubDate: 2015-08-07T02:10:06.388782-05:
      DOI: 10.1002/suco.201400076
       
  • The Effects of Alkali‐Silica Reaction on Mechanical Properties of
           Concretes with Three Different Types of Reactive Aggregates
    • Authors: Okpin Na; Yunping Xi, Edward Ou, Victor E. Saouma
      Abstract: This paper investigated the degradation of mechanical properties of concretes made of three types of aggregates affected by alkali‐silica reaction (ASR). To identify the reactivity of ASR of the three selected aggregates, three standard testing methods were used: ASTM C289, JASS 5N T‐603, and ASTM C1260. The test results showed that all three aggregates were potentially deleterious. A new acceleration method was proposed based on JASS 5N T‐603 and ASTM C1260 for concrete specimens. In the acceleration method, cylindrical concrete specimens were used, additional alkali material was added into the concrete mixture, and the specimens were stored under the condition similar to ASTM C1260. The preconditioned concrete specimens were then used for the evaluation of mechanical properties of the ASR affected concrete in terms of strength and stiffness. Test results showed that special attention must be made to the effects of two opposing mechanisms on strength and stiffness of concrete: hydration reactions and ASR. Hydration reactions enhance the mechanical properties, while ASR does the opposite. Length change of concrete specimens were also measured which showed that the basic trends for the length change and for the mechanical properties may be different. It is better to examine the effect of ASR on both length change and the mechanical properties. The size and reactivity of aggregate are very important factors for the mechanical properties of the ASR affected concretes. Within the two month testing period, the reactive fine aggregate may cause ASR expansion and the reactive coarse aggregates may not.
      PubDate: 2015-08-07T02:10:05.270837-05:
      DOI: 10.1002/suco.201400062
       
  • Life Cycle Analysis for Concrete Beams Designed with Cross Sections of
           Equal Durability
    • Authors: Lin Chen; Wenjun Qu, Peng Zhu
      Abstract: The durability at the corners of the cross section is relatively weak in the concrete beam of bridges; therefore, the reinforcements at the corners would corrode first. In order to delay the durability failure at the corners, measures such as application of corner concrete coating or adjustments of reinforcements at the corners should be taken. In this way, the durability resistance would be adjusted to be equal in the section, which is called equal durability design method. In this paper, the life cycle analysis of a component designed with equal durability and one designed in traditional way both in carbonation environment was conducted and compared. A probabilistic model of service life was established based on empirical degradation models. Service life distribution was calculated with Monte Carlo simulation method. Costs associated with durability failure were estimated based on the service life distribution. Related influencing factors were analyzed as well. Finally, life cycle cost analysis of the component designed with equal durability and the one designed in traditional way was conducted and compared. Results showed that the component designed with equal durability is more economic in the life cycle if the construction cost was controlled within about 1.1 times that of component designed traditionally.
      PubDate: 2015-07-20T06:20:18.816856-05:
      DOI: 10.1002/suco.201400117
       
  • Estimation of Transfer Lengths in Precast Pretensioned Concrete Members
           Based on a Modified Thick‐Walled Cylinder Model
    • Abstract: In pretensioned concrete members, prestress is introduced by the bond mechanism between prestressing tendon and surrounding concrete. Therefore, to secure the intended level of effective prestress in the tendon, sufficient bond stresses between the prestressing tendon and the concrete should be developed at release, for which a certain length from end of the pretensioned concrete member is required, and this required distance is defined as the transfer length of the prestressing tendon. In this study, the prestress introduction mechanism between the concrete and the prestressing tendon was mathematically formulated based on the thick‐walled cylinder theory (TWCT). On this basis, an analytical model for estimation of the transfer length was presented. The proposed model was also verified by comparing with test results collected from the literatures, and it was confirmed that the proposed model can accurately evaluate the effects of influential factors, such as diameter of prestressing tendon, compressive strength of concrete, concrete cover thickness, and magnitude of initial prestress, on the transfer lengths of prestressing tendons in various types of pretensioned concrete members.
      PubDate: 2015-07-15T05:20:18.517507-05:
      DOI: 10.1002/suco.201500049
       
  • Effect of ultrafine fly ash on properties of concretes containing
           construction and demolition wastes as coarse aggregates
    • Authors: Faiz U.A. Shaikh
      Abstract: This paper presents preliminary results on the effect of ultrafine fly ash (UFFA) on the properties of concretes containing recycled coarse aggregates (RCA) originated from construction and demolition (C&D) wastes. The effect of 10% UFFA on compressive strength, tensile strength, sorptivity and chloride ion permeability of concretes containing 25% and 50% RCA is evaluated at 7, 28 and 56 days. The addition of UFFA increased the compressive strength of recycled aggregates concretes at all ages up to 56 days. However, a slight reduction in the tensile strength of recycled aggregate concretes is observed. Concrete containing 25% RCA and 10% UFFA achieved 94% of the control concrete's compressive strength at 56 days. In both recycled aggregate concretes the sorptivity and chloride ion permeability are much lower at all ages due to the addition of 10% UFFA given the fact that it acts to promote the hydration and block the large capillary pores within the concrete.
      PubDate: 2015-07-14T09:55:12.735578-05:
      DOI: 10.1002/suco.201500030
       
  • Sulfate Attack Induced Damage and Micro‐Mechanical Properties of
           Concrete Characterized by Nano‐indentation Coupled with X‐Ray
           Computed Tomography
    • Authors: Chunxiang Qian; Yanfeng Nie, Tianji Cao
      Abstract: Sulfate attack is a serious problem for concrete served in marine environment. Sulfate attack can change the composition and microstructure of concrete and influence the mechanical and durable performances eventually. In this paper, the heterogeneity and mechanical properties of concrete exposed to sulfate was investigated from microscopic to mesoscopic scale. X‐ray computed tomography (XCT) and Nano‐indentation was adopted to define the defect zone and establish the relationship between interfacial transition zone (ITZ) and matrix of concrete (mortar). The experiments were based on concrete and mortar specimens in different strength. The results of XCT and Nano‐indentation indicated that the specimens had similar damaged degree regionally and a good correlation existed between the elastic modulus of the ITZ and mortar. The concrete could partition into three parts: the cracked zone with heavy damage, damaged zone and the undamaged zone. The elastic modulus of mortar phase and ITZ had a linear relation.
      PubDate: 2015-07-14T09:55:11.809917-05:
      DOI: 10.1002/suco.201400123
       
  • Scatter in the Shear Capacity of RC Slender Members without Web
           Reinforcement: Overview Study
    • Authors: Filippo Sangiorgio; Johan Silfwerbrand, Giuseppe Mancini
      Abstract: All researchers that have tested the shear capacity of RC members without stirrups have observed a large scatter in the results. The objective of this paper is to conduct an overview study of the causes to the great shear failure scatter of RC beams without stirrups. Thirteen groups of shear tests on comparable experiments, extracted from the ACI‐DAfStb evaluation database, are considered. The amount of data available is increased numerically. To this end, based on Eurocode 2 equations for shear resistance and shrinkage strain, a full probabilistic model according to JCSS Probabilistic Model Code is defined. A multivariate statistical evaluation of outcomes is then performed. The investigation highlights that both tensile strength of concrete and high values of shrinkage may be useful to be considered for more in‐depth studies of the phenomenon, whereas geometrical properties and concrete compressive strength seem to be less important or can even be neglected.
      PubDate: 2015-07-14T09:55:10.85857-05:0
      DOI: 10.1002/suco.201400107
       
  • A Theoretical Method for Calculating Compressive Arch Capacity of RC Beams
           against Progressive Collapse
    • Authors: Reza Abbasnia; Foad Mohajeri Nav
      Abstract: Compressive arch action is one of the main resistance mechanisms against progressive collapse in reinforced concrete (RC) buildings. Hence, many studies investigated the development of arching action in RC beams and frames but less attention has been paid to calculate the corresponding enhancement in structural capacity. In the present study, a theoretical method is introduced in order to calculate the arching capacity of RC beams and also to obtain a quantitative assessment about structural robustness against progressive collapse. The proposed method is validated using the experiments in the literature. The evaluation indicates that the introduced procedure could establish a reliable foundation for estimating the arching capacity of beams and also structural robustness.
      PubDate: 2015-07-14T09:55:09.84253-05:0
      DOI: 10.1002/suco.201400119
       
  • Behaviour of RC Beams with Openings Strengthened by Externally Bonded
           Carbon Fiber Reinforced Polymer (CFRP)
    • Authors: Siew Choo Chin; Nasir Shafiq, Muhd Fadhil Nuruddin
      Abstract: A detailed investigation was conducted to study the behaviour of reinforced concrete (RC) beams with large openings strengthened by externally bonded carbon fiber reinforced polymer (CFRP) laminates. A total of six simply‐supported beams consisting of two solid beams and four beams with openings were constructed and tested under four‐point bending. Each beam had a cross‐section of 120 × 300 mm and length of 2000 mm. A large opening was placed symmetrically in the mid‐span of the beams. Test parameters included the opening shape and size as well as the strengthening configuration of CFRP laminates. The study was conducted in both experimental testing and finite element analysis. Experimental results show that provision of a large opening at mid‐span reduces the beam capacity to about 50%. Strength gain due to strengthening using CFRP laminate in the experimental results obtained was in the range of 80–90%. Comparison between the finite element and experimental results were performed.
      PubDate: 2015-07-14T09:55:07.775283-05:
      DOI: 10.1002/suco.201400111
       
  • Shear strength of self‐compacting concrete beams with small amounts
           of stirrups
    • Abstract: In comparison with a vibrated concrete (VC) of the same strength class, the self‐compacting concrete (SCC) typically has lower coarse aggregate content and, eventually, smaller maximum aggregate size. This may result in reduction of aggregate interlock between fracture surfaces of SCC. Since the aggregate interlock plays an important role in the shear strength of slender beams, SCC beams may have a shear strength lower than similar VC beams, but studies on that subject are still limited. This article summarizes an experimental program that includes beams of high strength SCC and transverse reinforcement ratios around the minimum given by different codes, case that has not been investigated. The shear strengths of those beams are compared with the ones of VC beams with similar concrete compressive strength and small amounts of transverse reinforcement and also to the calculated ones according to different code procedures.
      PubDate: 2015-04-20T05:10:30.055478-05:
      DOI: 10.1002/suco.201400084
       
  • Concrete fatigue in composite dowels
    • Abstract: In modern bridge construction, steel‐concrete composite structures with composite dowels are being applied more than ever, especially for small and medium spans. In contrast to headed studs, in which initial steel cracks occur after only a few load cycles [1], [2], the lifetime of composite dowels is characterized by the compression of the multiaxially stressed concrete in front of the composite dowel. Here, plastic compression strains occur in the concrete, which accumulate over load cycles, leading to a cyclical increase of relative displacements in the connection. Certain proportions of these relative displacements, called inelastic slip, remain in the connection, even after the loading is released. The inelastic slip changes the characteristics of the static dowel curve. The initially rigid connection degrades over the lifetime, leading to redistributions of internal forces, which may be decisive for fatigue design. In order to consider the degradation of the composite connection a cyclic dowel curve can be used, which may be developed from the static dowel curve by introducing the inelastic slip. In this paper, the results of cyclic shear tests on different composite dowel geometries are presented. Here, the effect of load‐dependent parameters (upper load level and load range) was investigated. Furthermore, an engineering model for determining the cyclic dowel curve is presented, which was developed based on the results of experimental and numerical investigations.
      PubDate: 2015-04-02T05:40:05.295233-05:
      DOI: 10.1002/suco.201400120
       
  • ASR and sulphate performance of mortar containing industrial waste
    • Abstract: Greener concrete using adequate industrial waste is a preferred option for sustainable construction. Alkali‐silica reaction (ASR) and sulfate attack (SA) on concrete can be minimized by the use of mineral additions being particularly interesting if waste derived. Grits from a paper industry, waste glass and two types of biomass ash were used as 10% cement replacement in mortar and tested for ASR and SA. Results and Scanning Electron Mycroscopy observations were compared to plain mortar and to mortar containing commercial silica fume. All waste materials mitigated ASR compared to control mortar. Resistance to sulphates was increased for one of the biomass ashes used and especially for glass powder which surpassed silica fume. Therefore two of these waste materials seem to be promising to use as partial replacement material for cement leading to enhanced durability and thus contributing to sustainable construction.
      PubDate: 2015-03-20T04:40:16.421192-05:
      DOI: 10.1002/suco.201400095
       
 
 
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