JournalTOCs

International Journal of Advanced Structural Engineering
Journal Prestige (SJR): 0.399

Citation Impact (citeScore): 1
Number of Followers: 25

This is an Open Access Journal

Open Access journal
ISSN (Print) 2008-3556 - ISSN (Online) 2008-6695
Published by SpringerOpen

[228 journals]

Short-term deflection of RC beams using a discrete rotation approach
- Abstract: Abstract Quantifying the deflection of RC beams has been performed traditionally using full-interaction moment–curvature methods without considering the slip that takes place between the reinforcement and the surrounding concrete. This was commonly carried out by deriving empirically based flexural rigidities and using elastic deflection equations to predict the deformation of RC structures. However, as flexural and flexural/shear cracks form in RC beams with increase in applied load, the reinforcement steel begins to slip against the surrounding concrete surface causing the cracks to widen and ultimately increasing the deflection at mid-span. Current design rules cannot cope directly with the deformation induced by the widening of cracks. Because of that, this study focused on predicting the non-time dependent deflection of RC beams at both service and ultimate limit states using a mechanics-based discrete rotation approach. The mechanics-based solution was compared with experimental test results and well-established code methods to which a good agreement between the results was observed. The method presented accounts for the non-linear behavior of the concrete in compression, the partial-interaction behavior of the reinforcement, and the deflection was computed while considering the rotation of discrete cracks. Due to its generic nature, the method presented does not require any calibration with experimental findings on the member level, which makes it appropriate to quantify the deflection or RC structures with different types of concrete and novel reinforcement material.
  PubDate: 2019-12-01
Static analysis of tall buildings based on Timoshenko beam theory
- Abstract: Abstract In this paper, the continuum model, which is known as Kwan model, has been presented for the analysis of tall buildings that have been as an appropriate approximation of the overall behavior of the structure. Tall building was modeled as a cantilever beam and analyzed with the assumption of flexural behavior based on Euler–Bernoulli Beam Theory, then the displacement of floors was calculated. o consider the shear lag effects in the overall displacement of the structure, Timoshenko’s beam model has been considered and related relations were extracted. The lateral displacement formulas obtained and calculated for the framed tube system modeled by Kwan’s method. To verify the results, numerical models were created in software (ETABS) and statically were analyzed for lateral loading. Finally the results were compared with those obtained by computer analysis and the corresponding diagrams were presented. At the end, the shape factor formula has been developed to improve the results of the Timoshenko’s theory.
  PubDate: 2019-12-01
Numerical investigation of a new structural configuration of a concrete
barrier wall under the effect of blast loads
- Abstract: Abstract In this study, a non-linear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D, which is an extensive code dealing with explosion problems. A high explosive material (comp-B) is blasted against several concrete wall barriers. The model was first validated using referenced experimental tests and has shown good results. Several numerical models were carried out to study the effect of changing the shape of wall barrier from flat to convex curve and concave curve, and also investigated the effect of changing the angle of curvature. The results showed that changing the shape of a wall barrier from flat to convex curve has the best performance in mitigating the effect of blast waves. It is also concluded that convex walls with 60° angle of curvature have the best performance compared to other barrier walls.
  PubDate: 2019-12-01
Structural assessment of remodelled shells of Heinz Isler
- Abstract: Abstract Heinz Isler as the most famous contemporary shell designer has widely employed physical pre-modelling techniques for construction of many concrete shell structures. Through the physical approach to optimal form finding, Isler accomplished shell structures with robust performance. It would be interesting and beneficial to re-assess Isler’s shells, hence, this article attempts to study the structural performance of eight notable shells of Isler. Through reverse engineering and by the assistance of Rhino, MATLAB and Grasshopper, the precise geometry of Isler’s selected shells were modelled for the finite element analysis under their self-weight. The structural analysis was performed, with the parallel use of finite element software SAP2000 and Abaqus. The identical results of the two packages, further confirmed the accuracy of the analysis. The essential properties of various forms of the shells and their differences in behaviour were pinpointed and discussed within the calculations and the results were compared with the data of the genuine published references on Isler’s works. The internal forces, the amount of von Mises stresses, support reactions and the buckling loads of the shells are explored. The analyses revealed that, despite of their major membrane action, all the shells had negligible amount of bending moments, especially near the supports. However, in general, all the shells exhibited an appropriate performance under the applied actions. But, at the same time, they exhibited different buckling behaviour as a probable source of instability in them.
  PubDate: 2019-12-01
Investigation on cold-formed steel built-up new innovative hat-shaped
closed section under bending
- Abstract: Abstract The objective of this study is to make the experimental and finite element simulations of buckling behaviour of cold-formed steel (CFS) built-up hat-shaped closed section under simply supported end condition subjected to two-point loading. Numerical simulation is carried out using the software ABAQUS. The test result is compared with numerical results and good correlation is achieved. Next, for validation, a series of parametric studies are carried out using the validated numerical model, such as the effect of length, depth, width, thickness and angle of the inclined element. The local buckling and the interaction of local and flexural buckling are studied. To end with, a design equation is proposed in accordance with the direct strength method specification for CFS structure.
  PubDate: 2019-12-01
Modal identification of localised damage in beams and trusses:
experimental and numerical results
- Abstract: Abstract The paper discusses the possibility of detecting local damages in complex structures typical of civil engineering, as multispan beams and trusses. Namely, it describes a procedure to identify localised cracks in structures in the elastic range of behaviour using only the values of natural frequencies in the intact configuration and in the damaged one evaluated by means of dynamic tests. The error minimisation procedure described in the paper selects the solution within a set of finite element models that simulate a range of positions and levels of damage, by identifying the damaged configuration as the one whose modal frequencies minimise the least-square difference with the measured data. The accuracy of the method is first investigated by applying it to the damage detection of a two-span steel beam, whose modal frequencies were obtained by means of experimental tests. To explore the accuracy of the proposed procedure, numerically simulated data with random noise were also generated for several positions and levels of damage and for different values of the random noise. The procedure was then extended, by means of numerical simulations, to the case of a beam with two localised damages. Finally, the procedure proposed for multispan beams is adapted to the damage identification of plane truss structures.
  PubDate: 2019-12-01
Seismic performance of existing water tank after condition ranking using
non-destructive testing
- Abstract: Abstract There has been a collaborative attempt to address the seismic vulnerability of existing structures in India after an earthquake in Bhuj, Gujarat, in 2001. Seismic diagnosis and seismic retrofit for the existing tanks have become a remarkable issue to be worked since deterioration is a cosmopolitan and natural phenomenon. It is important to know the exact reason for distress and type of distress. To manage such issues, a proper method of repair and rehabilitation with detailed plans and methodology is required. This paper is aimed at evolving systematic investigation metrology for condition ranking procedure based on the analytical hierarchy process (AHP) and strengthening by various retrofitting strategies. For that case study, an existing elevated water tank is considered, which was designed according to state of the art over 40 years ago as per old Indian Standard (IS) code. The ranking assessment of the elevated service reservoir was carried out using different non-destructive tests (NDTs). DER, i.e., degree (D), extent (E) and relevancy (R) rating technique was employed to find out the condition index of the elevated service reservoir (ESR). After finding the condition ranking of the existing structure, an analysis was carried out using SAP 2000 to find the present-day seismic requirements using IS codes. After knowing the seismic demand of the water tank, various retrofitting methods were adopted for improving the drift capacity and flexural capacity of the structure. The results were finally used to address some of the critical issues of the seismic response of the retrofitted structure in terms of a time period, mode shapes, base shear, displacement, acceleration, and velocity. From the case study result of seismic retrofit for the existing elevated water tank, it is confirmed that a relatively simple seismic retrofit method is effective to keep the tank functional after an earthquake.
  PubDate: 2019-12-01
Numerical analysis and experimental testing of ultra-high performance
fibre reinforced concrete keyed dry and epoxy joints in precast segmental
bridge girders
- Abstract: Abstract Although ultra-high performance fiber reinforced concrete (UHPFRC) has been used recently as a sustainable construction technique for many precast segmental bridges (PSBs), no exhaustive numerical and experimental studies exist to assess the shear capacity and failure pattern of the joints in these bridges. Hence, to accurately investigate the shear behavior of the joints in UHPFRC precast segmental bridges, a numerical analysis model based on finite-element code was established in this study. Concrete damaged plasticity model was used to analyze the UHPFRC joint models by considering all the geometries, boundaries, interactions and constraints. In this paper, the numerical model was calibrated by two full-scale UHPFRC keyed dry and epoxy joints under confining pressure effect. The excellent agreement between the numerical results and experimental data demonstrated the reliability of the proposed numerical model. The validated numerical model was then utilized to investigate the parameters affecting shear behaviour of the joints in PSBs. For this purpose, 12 FE models were analyzed under different variable parameters namely, number of shear keys, confining stress, and types of joints (dry or epoxy). Furthermore, the numerical results were also compared with the five existing shear design provision models available in literature in terms of ultimate shear capacity.
  PubDate: 2019-12-01
Embedded carbon fiber-reinforced polymer rod in reinforced concrete frame
and ultra-high-performance concrete frame joints
- Abstract: Abstract Beam–column joints play an important role in providing lateral stiffness and integrity of frames during dynamic loading such as earthquake. In the high humidity areas, during functioning of the building cracks occur, which leads to the corrosion of the reinforcement due to the environmental exposures. Therefore, one of the main failures mechanism of building during an earthquake is caused by easily yielding of corroded steel reinforcement, which leads to reduce functionality of the frame joints in transferring the loads. This study proposed a new design to reinforce the beam-column joints with embedded carbon fiber-reinforced polymer (CFRP) rods, due to their extremely high strength and stiffness, along with the fact that they will not rust or corrode and very light weight. CFRP rods are used in reinforced concrete (RC) frame and ultra-high-performance concrete (UHPC) frame subjected to dynamic load. The prototype of the proposed design is constructed as frame with conventional concrete and frame with UHPC material to conduct experiments Test as well as numerical analysis to evaluate the performance of the proposed joints under dynamic loads. The results showed improvement in the performance of the frames reinforced with embedded CFRP in joints in terms of lateral load resistance capacity, ductility behaviour, overall stiffness, and failure mechanism.
  PubDate: 2019-12-01
Influence of ground motion duration on ductility demands of reinforced
concrete structures
- Abstract: Abstract This article investigates the level of influence that strong motion duration may have on the inelastic demand of reinforced concrete structures. Sets of short-duration spectrally equivalent records are generated using as target the response spectrum of an actual long-duration record. The sets of short-duration records are applied to carefully calibrated numerical models of the structures along with the target long-duration records. The input motions are applied in an incremental dynamic analysis fashion, so that the duration effect at different levels of inelastic demand can be investigated. It was found that long-duration records tend to impose larger inelastic demands. However, such influence is difficult to quantify, as it was found to depend on the dynamic properties of the structure, the strength, and stiffness degrading characteristics, the approach used to generate the numerical model and the seismic scenario (target spectrum). While for some scenarios, the dominance of the long record was evident; in other scenarios, the set of short records clearly imposed larger demands than the long record. The detrimental effect of large strong motion durations was mainly observed in relatively rigid structures and poorly detailed flexible structures. The modeling approach was found to play an important role in the perceived effect of duration, with the lumped plasticity multilinear hysteretic models suggesting that the demands from the long records can be up to twice the inferred from distributed plasticity fiber models.
  PubDate: 2019-12-01
Numerical comparison on the efficiency of conventional and hybrid
buckling-restrained braces for seismic protection of short-to-mid-rise
steel buildings
- Abstract: Abstract Buckling-restrained brace (BRB) is a specific kind of bracing system which has an acceptable energy dissipation behavior in a way that would not be buckled in compression forces. However, considerable residual deformations are noticed in strong ground motions as a result of the low post-yield stiffness of the BRBs. The seismic performance of a modern lateral load resisting system, which is called the hybrid BRB, and its conventional counterpart are assessed and compared in this paper. Multiple plates with different stress–strain behavior are used in the core of this new innovative system, and this is its difference with the existent BRBs. Nonlinear static and incremental dynamic analyses are carried out for three building frames with different structural heights, which use conventional and hybrid BRB systems. To carry out response history analyses, the FEMA P695 far-field earthquake record set was adopted in different hazard levels. The hybrid BRBs are shown to have superior seismic performance in comparison with the conventional systems based on the response modification factor and the damage measures including residual displacements and inter-story drift ratios.
  PubDate: 2019-12-01
Formulation of a new finite element based on assumed strains for membrane
structures
- Abstract: Abstract In this paper, a new triangular membrane finite element with in-plane drilling rotation has been developed using the strain-based approach for static and free vibration analyses. The proposed element, having three degrees of freedom at each of the three corner nodes, is based on assumed strain functions satisfying both compatibility and equilibrium equations. Numerical investigations have been conducted using several tests, including static and free vibration problems, and the obtained results are compared with analytical and numerical available solutions. It is found that efficient convergence characteristics and accurate results can be achieved using the developed element.
  PubDate: 2019-12-01
The efficiency of using CFRP as a strengthening technique for reinforced
concrete beams subjected to blast loading
- Abstract: Abstract Some structures may be subjected to blast loading while in service. This may cause damage or failure to the structural elements. This paper examines the performance of reinforced concrete beams using carbon fiber reinforced polymer (CFRP) when subjected to blast loading. The experimental data including damage and deflection were collected from a previous investigation and numerical analysis was then performed using ABAQUS software. Furthermore, the single degree of freedom (SDOF) model was used to complement the findings from numerical analysis. Following the good correlation between the experimental and numerical data, further analysis was performed on reinforced concrete beams strengthened with carbon fiber-reinforced polymer (CFRP). Using CFRP was found to enhance the load capacity and energy absorption and to reduce the central deflection. In addition, Iso-Damage curves were produced for each beam, thus allowing the assessment of damage to be predicted.
  PubDate: 2019-12-01
Numerical modeling of elastomeric seismic isolators for determining
force–displacement curve from cyclic loading
- Abstract: Abstract The ideal performance of seismic isolating systems during the past earthquakes has proved them to be very useful in protecting structures against earthquakes. The cyclic loading experimental tests are an important part in the process of completing the design of the isolators, yet they are very expensive and time consuming. Using the accurate analytical modeling of hysteresis tests and knowing the limitations and the amount of error of the finite elements model and its effect on designing the isolated structure make it possible to reduce the financial and time expenses involved in designing seismic isolators along with experimental tests. In the present study, the cyclic loading of two different isolating systems, namely, the high damping rubber bearing (HDRB) and lead rubber bearing (LRB) have been modeled and analyzed in ABAQUS and the outcomes were compared with the experimental results attained by other researchers. Regarding the fact that the most important and complicated component of the elastomeric isolating system is rubber, it was modeled using various strain energy functions. Other factors affecting the finite elements models of elastomeric isolators were also studied. After comparing the effective stiffness of the experimental sample with the analytical model of HDRB, the Yeoh function had the best performance in determining the effective stiffness of the isolating system with an error of less than 7%. In studying LRBs, too, three types of bearings with different dimensions and lateral strain values were studied; the polynomial function in shear strain value of 150% had the best performance in estimating effective stiffness and damping with errors of less than 3% and 18%, respectively.
  PubDate: 2019-09-01
Evaluation and upgrading web-gap distortion retrofits in steel girder
bridges
- Abstract: Abstract Distortion-induced fatigue cracking in the unstiffened web-gap of cross-frame diaphragms is the most prevalent type of cracking in steel girder bridges. Multi-steel girder bridges experience differential deflection between adjacent girders when subject to vertical loads resulting in a driving force in cross-frame diaphragms. The driving force developed in the cross-frame legs leads to out-of-plane distortion of the web-gap which results in high stress concentrations at the area, following by fatigue damages. This paper introduces an innovative method to retrofit web-gap distortion cracking, upgrade existing retrofits, and compare its effectiveness with two common retrofit techniques. The method involves cutting the existing connection plate and using angles to attach the disconnected part of the connection plate to the web. The method intends to eliminate the local high stresses at the connection plate end with considering minimal interference in original connection design and load path. Also, two other conventional repair methods were investigated, slot method and top-angle measure, to use as a basis for comparing the methods effectiveness. Laboratory testing was performed on a small-scale steel bridge bay by applying a vertical displacement to the free end of a cross-frame diaphragm to simulate the differential deflection between two adjacent girders in real bridges. The results from the testing were compared to findings from finite element analyses (FEA). Test results as well as FEA results for all investigated retrofit techniques are presented herein. Results showed that the newly developed slot-angle technique has significant potential for effectively reducing the stress concentrations in the web-gap region by removing the location of initial stress concentrations and redistributing those stresses over a wider area.
  PubDate: 2019-09-01
Influence of the soil properties on the seismic response of structures
- Abstract: Abstract The objective of this study is to model the interaction between a concrete wall and a soil under seismic loading using the finite element method. The stiffness matrix of the soil is integrated to that of the structure to formulate the stiffness matrix of the entire system. To simulate the dynamic of soil–structure interaction, a numerical program was developed for this concern. So to resolve governed dynamic equations, the central difference method is used to compute displacement, velocity, and acceleration fields of soil, interface medium, and concrete wall nodes. The significance of soil foundation–structure interaction over fixed-base structure analysis showed that the integration of soil and foundation produces considerable changes in the seismic response. Obtained results using the soil–structure model and impedance functions are compared to those of fixed-base structure. The purpose is to calibrate the effects of soil properties and the soil–structure interaction on the seismic response of the structure and on the interaction medium.
  PubDate: 2019-09-01
Large deformation analysis of plane-stress hyperelastic problems via
triangular membrane finite elements
- Abstract: Abstract A finite-element formulation based on triangular membranes of any order is proposed to analyze problems involving highly deformable hyperelastic materials under plane-stress conditions. The element kinematics is based on positional description and the degrees of freedom are the current plane coordinates of the nodes. Two isotropic and nonlinear hyperelastic models have been selected: the compressible neo-Hookean model and the incompressible Rivlin–Saunders model. The constitutive relations and the consistent tangent operator are condensed to the compact 2D forms imposing plane-stress conditions. The resultant algorithm is implemented in a computer code. Three benchmark problems are numerically solved to assess the formulation proposed: the Cook’s membrane, involving bending, shear, and a singularity point; a partially loaded membrane, which presents severe mesh distortion and large compression levels; and a rubber sealing, which is a more realistic problem. Convergence analysis in terms of displacements, applied forces, and stresses is performed for each problem. It is demonstrated that mesh refinement avoids locking problems associated with incompressibility condition, bending-dominated problems, stress concentration, and mesh distortion. The processing times are relatively small even for fifth-order elements.
  PubDate: 2019-09-01
Shear buckling behavior of a plate composite girder using concrete-filled
steel tube structures
- Abstract: Abstract In this study, the shear buckling behavior of plate girders using concrete-filled steel tube structure was verified by nonlinear finite element analysis using CEB-FIP 1990 code. In addition, shear buckling tests were carried out on the model specimens and compared with the analysis. As a result, it was confirmed that the proposed plate girder improved the shear buckling resistance compared to the general plate girder. Also, by comparing the test results with the analysis, we propose that the proposed CEP-FIP code is a reasonable analysis. Particularly, as a result of comparing the maximum deflection displacement of the plate girder, it was found that the proposed girder improved the shear buckling resistance performance due to the confinement effect of the concrete-filled steel tube structure than general plate girder.
  PubDate: 2019-09-01
Effects of concrete parameters in the lateral stiffness of reinforced
concrete squat walls
- Abstract: Abstract The basis for the effective stiffness values or expressions and their applicability to nuclear power plant elements is not clearly presented in current seismic standards. This paper studies the effective stiffness of reinforced concrete (RC) squat walls under lateral loads. RC squat walls have height-to-length ratios less than or equal to 2. Prediction of the seismic response and proper capturing of the effective stiffness of squat walls are a challenging task, since these walls exhibit a shear-dominated behavior with strong coupling between shear and flexure responses. Finite-element models of several RC squat walls are developed using the commercial software Abaqus. The main objective of these models is to predict the lateral stiffness of RC squat walls appropriately and to identify the parameters that have main influence in the lateral stiffness of these walls. The results from analytical modeling are compared with the results of experimental tests available in the literature. Available expressions in current seismic standards and in the literature for the calculation of effective stiffness for RC squat walls are also evaluated. Key parameters influencing the effective stiffness are identified during the nonlinear analyses and from existing experimental data.
  PubDate: 2019-09-01
Optimization of seismic response of steel structure using negative
stiffness damper
- Abstract: Abstract Earthquakes of greater magnitude can cause stark destruction. Seismic protection of structures is one important tool to minimize damages and total collapse of structures. Researchers have made many attempts to achieve this goal with various techniques and one such strategy of seismic response control developed is introducing true negative stiffness in the structure. True negative stiffness is introduced with the help of negative stiffness damper (NSD). The NSD generates force in the direction of the displacement and hence it is called negative stiffness. The present study focuses on modelling NSD device in a commercial software tool (ETABS 2016). Further the device is implemented on 2D steel frame models and seismic parameters such as base shear, storey displacement and top storey acceleration are studied.
  PubDate: 2019-09-01