• Advances in concrete construction
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• v.10 no.1
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• pp.35-48
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• 2020

This paper deals with a comparative study among three different rehabilitation techniques, namely, (i) carbon fibre reinforced polymer (CFRP), (ii) glass fibre reinforced polymer (GFRP) and (iii) ferrocement on the flexural strengthening of reinforced cement concrete (RCC) beams. As these different techniques have to be compared on a level playing field, tensile coupon tests have been carried out initially for GFRP, CFRP and ferrocement and the number of layers required in each of these composites in terms of the tensile strength. It was found that for the selected constituents of the composites, one layer of CFRP was equivalent to three layers of GFRP and five layers of wiremesh reinforcement in ferrocement. Rehabilitation of RCC beams using these equivalent laminates shows that all the three composites performed in a similar way and are comparable. The parameters selected in this study were (i) the strengthening material and (ii) the level of pre-distress induced to the beams prior to the rehabilitation. It was noticed that, as the levels of pre-distress decreases, the percentage attainment of flexural capacity and flexural stiffness of the rehabilitated beams increases for all the three selected composites used for rehabilitation. Load-deflection behavior, failure modes, energy absorption capacity, displacement ductility and curvature ductility were compared among these composites and at different distress levels for each composite. The results indicate that ferrocement showed a better performance in terms of ductility than other FRPs, and between the FRPs, GFRP exhibited a better ductility than the CFRP counterpart.

• Computers and Concrete
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• v.16 no.4
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• pp.625-642
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• 2015

Prestressed concrete bridges with corrugated steel webs have emerged as one of the promising bridge forms. This structural form provides excellent structural efficiency with the concrete flanges primarily taking bending and the corrugated steel webs primarily taking shear. In the design of this type of bridges, the flexural ductility and deformability as well as strength need to be carefully examined. Evaluation of these safety-related attributes requires the estimation of full-range behaviour. In this study, the full-range behaviour of beam sections with corrugated steel webs is evaluated by means of a nonlinear analytical method which uses the actual stress-strain curves of the materials and considers the path-dependence of materials. In view of the different behaviour of components and the large shear deformation of corrugated steel webs with negligible longitudinal stiffness, the assumption that plane sections remain plane may no longer be valid. The interaction between shear deformation and local bending of flanges may cause additional stress in flanges, which is considered in this study. The numerical results obtained are compared with experimental results for verification. A parametric study is undertaken to clarify the effects of various parameters on ductility, deformability and strength.

• Earthquakes and Structures
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• v.22 no.3
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• pp.231-243
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• 2022

Beam-column joints (BCJs) are recognized among the most crucial zones in reinforced concrete structures, as they are the critical elements subjected to a complex state of forces during a severe earthquake. Under such conditions, BCJs exhibit behaviors with impacts that extend to the whole structure and significantly influence its ductility and capability of dissipating energy. The focus of this paper is to investigate the effect of undamaged transverse beam (secondary beams) on the ductility of concrete BCJs reinforced with conventional steel and shape memory alloys bars using pushover analysis at tip of beam under different axial load levels at the column using a nonlinear finite element model in ABAQUS environment. A numerical model of a BCJ was constructed and the analysis outcomes were verified by comparing them to those obtained from previous experiments found in the literature. The comparison evidenced the capability of the calibrated model to predict the load capacity response of the joint. Results proved the ability of undamaged secondary beams to provide a noticeable improvement to the ductility of reinforced concrete joints, with a very negligible loss in load capacity. However, the effect of secondary beams can become less significant if the beams are damaged due to seismic effects. In addition, the axial load was found to significantly enhance the performance of BCJs, where the increase in axial load magnified the capacity of the joint. However, higher values of axial load resulted in greater initial stiffness of the BCJ.

• Steel and Composite Structures
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• v.39 no.3
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• pp.337-352
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• 2021

The study presented experimental and numerical investigation on the seismic performance of steel reinforced concrete (SRC) L-shaped column- reinforced concrete (RC) beam joints. Various parameters described as steel configuration form, axial compressive ratio, loading angle, and the existence of slab were examined through 4 planar joints and 7 spatial joints. The characteristics of the load-displacement response included the bearing capacity, ductility, story drift ratio, energy-dissipating capacity, and stiffness degradation were analyzed. The results showed that shear failure and flexural failure in the beam tip were observed for planar joints and spatial joint, respectively. And RC joint with slab failed with the plastic hinge in the slab and bottom of the beam. The results indicated that hysteretic curves of spatial joints with solid-web steel were plumper than those with hollow-web specimens. The capacity of planar joints was higher than that of space joints, while the opposite was true for energy-dissipation capacity and ductility. The high compression ratio contributed to the increase in capacity and initial stiffness of the joint. The elastic and elastic-plastic story deformation capacity of L-shaped column frame joints satisfied the code requirement. A design formula of joint shear resistance based on the superposition theory and equilibrium plasticity truss model was proposed for engineering application.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.273-280
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• 2011

Ten high-strength concrete beam specimens, which have various combinations of different types of flexural reinforcement and short fibers were constructed and tested. Six beams were reinforced with two layers of steel, CFRP, and GFRP bar combinations. The other four beams were reinforced with two layers of single type CFRP and GFRP bars, with steel and synthetic short fibers. An investigation was performed on the influence of the parameters on the load-carrying capacity, post cracking stiffness, cracking pattern, deflection behavior, and ductility. The low post cracking stiffness, large deflection, deep crack propagation, large crack width, and low ductility of FRP bar-reinforced beams were controlled and improved by positioning steel bars in the inner layer of the FRP bar layer. In addition, the addition of fibers increased the first-cracking load, ultimate flexural strength, and ductility as well as the deep propagating cracks were controlled in the FRP bar-reinforced concrete beams. The increased ultimate concrete strain of fiber-reinforced concrete should be determined and considered when FRP bar-reinforced concrete members with fibers are designed.

• Earthquakes and Structures
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• v.26 no.6
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• pp.449-461
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• 2024

The vertical reinforcement connection between the precast reinforced concrete shear wall and the cast-in-place reinforced concrete member is vital to the performance of shear walls under seismic loading. This paper investigated the structural behavior of three precast reinforced concrete shear walls, with different levels of connection (i.e., full connection, partial connection, and no connection), subjected to quasi-static lateral loading. The specimens were subjected to a constant vertical load, resulting in an axial load ratio of 0.4. The crack pattern, failure modes, load-displacement relationships, ductility, and energy dissipation characteristics are presented and discussed. The resultant seismic performances of the three tested specimens were compared in terms of skeleton curve, load-bearing capacity, stiffness, ductility, energy dissipation capacity, and viscous damping. The seismic performance of the partially connected shear wall was found to be comparable to that of the fully connected shear wall, exhibiting 1.7% and 3.5% higher yield and peak load capacities, 9.2% higher deformability, and similar variation in stiffness, energy dissipation capacity and viscous damping at increasing load levels. In comparison, the seismic performance of the non-connected shear wall was inferior, exhibiting 12.8% and 16.4% lower loads at the yield and peak load stages, 3.6% lower deformability, and significantly lower energy dissipation capacity at lower displacement and lower viscous damping.

• Steel and Composite Structures
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• v.43 no.5
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• pp.565-579
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• 2022

This study investigated the yielding capacity and performance of seismic dampers constructed with steel ring plates using numerical and analytical approaches. This study aims to provide an analytical relationship for estimating the yielding capacity and initial stiffness of steel ring dampers. Using plastic analysis and considering the mechanism of plastic hinge formation, a relation has been obtained for estimating the yielding capacity of steel ring dampers. Extensive parametric studies have been carried out using a nonlinear finite element method to examine the accuracy of the obtained analytical relationships. The parametric studies include investigating the influence of the length, thickness, and diameter of the ring of steel ring dampers. To this end, comprehensive verification studies are performed by comparing the numerical predictions with several reported experimental results to demonstrate the numerical method's reliability and accuracy. Comparison is made between the hysteresis curves, and failure modes predicted numerically or obtained/observed experimentally. Good agreement is observed between the numerical simulations and the analytical predictions for the yielding force and initial stiffness. The difference between the numerical models' ultimate tensile and compressive capacities was observed that average of about 22%, which stems from the performance of the ring-dampers in the tensile and compression zones. The results show that the steel ring-dampers are exhibited high energy dissipation capacity and ductility. The ductility parameters for steel ring-damper between values were 7.5 to 4.1.

• Steel and Composite Structures
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• v.16 no.3
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• pp.253-267
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• 2014

Based on the test on a 1/2.5-scaled model of a two-bay and three-story inner frame composed of reinforced concrete beams and lattice steel reinforced concrete (SRC) irregular section columns under low cyclic reversed loading, the failure process and the features of the frame were observed. The subsequence of plastic hinges of the structure, the load-displacement hysteresis loops and the skeleton curve, load bearing capacity, inter-story drift ratio, ductility, energy dissipation and stiffness degradation were analyzed. The results show that the lattice SRC inner frame is a typical strong column-weak beam structure. The hysteresis loops are spindle-shaped, and the stiffness degradation is insignificant. The elastic-plastic inter-story deformation capacity is high. Compared with the reinforced concrete frame with irregular section columns, the ductility and energy dissipation of the structure are better. The conclusions can be referred to for seismic design of this new kind of structure.

• Steel and Composite Structures
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• v.44 no.6
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• pp.789-801
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• 2022

In order to study the influence of loading angles on seismic performance of steel reinforced concrete (SRC) special-shaped columns, cyclic loading tests and finite element analysis (FEA) were both carried out. Seven SRC special-shaped columns, including two L-shaped columns, three T-shaped columns and two cross-shaped columns, were tested, and the failure patterns of the columns with different loading angles were obtained. Based on the tests, the FEA models of SRC special-shaped columns with different loading angles were established. According to the simulation results, hysteretic curves and seismic performance indexes, including bearing capacity, ductility, stiffness and energy dissipation capacity, were analyzed in detail. The results showed that the failure patterns were different for the columns with the same section and different loading angles. With the increasing of loading angles, the hysteretic curves became fuller and the bearing capacity and initial stiffness appeared increasing tendency, but the energy dissipation capacity changed insignificantly. When the loading angle changed, the ductility got better with the larger area of steel at the failure side for the unsymmetrical section and near the neutral axis for the symmetrical section, respectively.

• Structural Engineering and Mechanics
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• v.90 no.5
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• pp.435-446
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• 2024

The use of cold-formed steel members is increasing day by day, especially in regions where earthquake effects are intensively experienced. Among cold-formed steel members (CFS), "channel" members are used more than other crosssectional members, especially in buildings or industrial structures. In recent years, several studies have been carried out on the axial load and flexural performance of these members under monotonic loading. In this study, CFS beam-column members were cyclically and monotonically loaded under combined axial load and biaxial bending moments, and their buckling behavior, load bearing capacity, stiffness, ductility, and energy absorption capacity were determined. For this purpose, monotonic and cyclic loading experiments were carried out on 30 CFS channel members at 15 different eccentricities. Then, material properties were determined by axial monotonic tensile and very low cycle fatigue tests for use in numerical studies. From the experimental results, the buckling modes, bearing capacities, ductility, stiffness, and energy absorption capacities of the members were obtained. The characteristics of the members were compared according to the stress state of the lips. According to the data obtained from the displacement transducer placed on the lips and on the back of the web, information about the buckling mode and curvature of the members was obtained. Finally, monotonic, and cyclic loading results were compared to determine the differences in the buckling behavior of the members.