Behavior Of Concrete Shear Walls Research Articles

Influence of Axial Load and Transverse Impact Velocity on the Behavior of Concrete Shear Walls Reinforced with GFRP Bars

A three-dimensional numerical model was established to investigate the impact resistance of concrete shear walls reinforced with fiber-reinforced polymer (FRP) bars, considering the strain rate effect of FRP reinforcement and concrete materials. After validating the numerical model, the failure mechanism of concrete shear walls reinforced with glass fiber–reinforced polymer (GFRP) bars under impact load was studied. The influence of impact velocity and axial load ratio on the impact resistance of GFRP-reinforced concrete shear walls was discussed. The results showed that GFRP-reinforced concrete walls have similar behavior to conventional reinforced concrete walls under impact loadings. The former experienced more considerable deformation due to the lower elastic modulus of GFRP bars. The peak and residual displacement at the center of the wall increased linearly with the impact energy. In addition, the peak value, plateau value, impulse, and duration of impact force grew linearly with respect to impact velocity. The proportion of energy absorbed by concrete increased in the cases of larger impact velocity. From the perspective of the internal force envelope along the wall height, the dangerous sections under impact were located at both ends of the wall under axial load. The peak value of the internal force improved with an increase of the axial load ratio. When the axial load ratio was between 0.3 and 0.4, the impact force of the wall reached the largest, and the minimum deformation occurs, indicating the best impact resistance of the shear walls. As the axial load ratio increased from 0.1 to 0.5, the total energy consumption increased from 68% to 89%, among which the external force work is 57 times that of the 0.1 axial load ratio, aggravating the failure of walls.

Quasi‑static Cyclic In‑plane Testing of Slender GFRP-Reinforced Concrete Shear Walls

Using Glass fiber-reinforced polymer (GFRP) bars as a replacement for conventional steel bars is one of the most potential solutions to steel-corrosion-related problems in concrete. Their durability and high strength-to-weight ratio make them a cost-effective and applicable alternative to conventional steel bars. This study investigates the characteristic behavior of concrete shear walls reinforced with steel, GFRP, and a hybrid scheme of steel and GFRP bars under seismic loading. Six full-scale RC shear walls with an aspect ratio of 3.25 were tested under pseudo-static reversed-cyclic lateral load to investigate the potential of a hybrid reinforcement scheme of steel-GFRP to improve the seismic behavior of slender RC shear walls. The overall performance of each tested wall was characterized by investigating the hysteretic response, crack propagation, lateral load capacity, and energy dissipation behavior.

Effect of spiral transverse bars on structural behavior of concrete shear walls reinforced with GFRP bars

In the present experimental study, the effect of spiral transverse bars on failure mode and structural behavior of concrete shear walls reinforced with GFRP bars was investigated. Six full-scale shear walls in two aspect ratios (1.08 and 1.75) were tested under constant axial load and cyclic lateral loading. Two specimens were reinforced with longitudinal and transverse steel bars (SRCW1.08 and SRCW1.75), two specimens reinforced with longitudinal and transverse GFRP bars (GRCW1.08 and GRCW1.75), and two specimens reinforced with longitudinal and spiral transverse GFRP bars (S-GRCW1.08 and S-GRCW1.75) were investigated. The experimental results indicate that the spiral transverse bars at two aspect ratios of specimens led to an increase in shear capacity, ultimate lateral displacement, and a change in the failure mode from compression failure to rupture of longitudinal bars in shear walls reinforced with GFRP bars. Comparing GRCW1.08, S-GRCW1.08, and GRCW1.75 with S-GRCW1.75 indicated that parameters such as ultimate lateral loading 23.1 and 9.2%, ultimate lateral displacement 20.1 and 20.4%, cumulative dissipation energy 48.7 and 54.8%, and displacement ductility ratio 18.6 and 20.2% were increased.

Numerical modelling strategy for predicting the response of reinforced concrete walls using Timoshenko theory

In recent decades, different macro-models have been proposed for simulating the behaviour of concrete shear walls because of their significant role in the seismic performance of urban buildings. The ability of Timoshenko's beam theory to evaluate the behaviour of slender and moderate-aspect-ratio concrete shear walls was evaluated in this work. For this purpose, a non-linear displacement-based Timoshenko fibre element was first added to OpenSees software. A new constitutive model based on modified compression field theory was used for the stress–strain relationship of the materials. To validate the element and the materials used, the results of the numerical model were compared with a set of laboratory tests of concrete shear walls subjected to cyclic and seismic loads (shaking table tests). Evaluation of the numerical model and the experimental results revealed that the analysis procedure used to model the reinforced concrete walls predicted their overall and local responses with acceptable accuracy. It can thus be used as a reliable tool for the analysis of slender and moderate-aspect-ratio concrete shear walls.

Seismic behavior of concrete shear walls with bolted end-plate DfD connections

An experimental study was carried out to investigate the seismic behavior of newly developed concrete shear walls with the bolted end-plate design for deconstruction (DfD) connections, with the aim of applying reused structural components to mid-rise buildings. This DfD connection was characterized by pre-buried end-plates and welding shear studs. The proper design was proposed to facilitate the application for future deconstruction and reconstruction. Four concrete shear walls with different aspect ratios were designed and tested according to a cyclic loading test to evaluate the seismic behavior. The principle of reuse and recycle were firstly both applied to concrete structures in the domain of this research. It can be found that the existence of the proposed DfD connection changed the cracking pattern and failure modes of the concrete shear wall. The interface between the DfD connection and the concrete wall turned to be the weak part of the whole structure. Moreover, the proposed DfD connection had a limited effect on the load bearing and transferring mode for the slender shear wall, while significantly changed the load resistance of the squat shear wall. The disassembly and assembly for the proposed shear wall with DfD connections were calibrated during the test process, proving that deconstruction and reconstruction purpose for this shear wall can be achieved.

Shear behavior of concrete shear walls with CFRP grids under lateral cyclic loading

Carbon fiber reinforced polymer (CFRP) is ideal for use in new construction owing to its light weight, high strength, and linear elasticity properties. CFRP grid is a common form of reinforcement that can enhance the structural integrity of components. In this study, six concrete shear walls, including one steel reinforced concrete (RC) wall and five walls reinforced with CFRP grids in two reinforcement configurations (vertically or horizontally laid), were tested until failure under cyclic loading. The comparison parameters include the aspect ratio, horizontal reinforcement ratio, and reinforcement configuration. The six specimens with aspect ratios of 1.0 and 1.4 experienced diagonal compression shear failure. The specimens with CFRP grids exhibited higher shear resistance in terms of a larger lateral drift, load capacity, strain, and less residual deformation, in particular, for walls with horizontal grids compared to conventional RC shear wall. The horizontally arranged CFRP grids significantly reduced the deformation concentration and improved the concrete confinement. Theoretical formulas based on the truss-arch model were developed to calculate the shear capacity of the concrete shear walls with CFRP grids.

Modelling the behaviour of concrete shear walls with BFRP reinforcement

Corrosion of steel reinforcement in concrete structures is one of the main challenges for the construction industry. FRP reinforcement could be used as alternative to steel reinforcement providing several advantages, such as high resistance to corrosion, high tensile strength and opportunity for developing a more ductile mode of destruction. The last characteristic is extremely beneficial in the aspect of lateral load resisting systems including RC shear walls. The presented modelling results consist of preparing finite element models of reinforced concrete shear walls utilizing Ansys 19.2 - Solid65 element which is capable of both cracking and crushing. The results were verified with experimental medium-scale concrete shear walls reinforced with steel and BFRP bars. The models were loaded under cyclic lateral loading following a modified ATC (Applied Technology Council guidelines for seismic testing) 24 protocol. BFRP reinforced models developed similar ultimate capacity and significantly higher energy dissipation in comparison with steel reinforced models. The promising results could provide a momentum toward construction of shear walls using FRP reinforcement with the aims of improving durability and energy dissipation.

Seismic assessment of existing RC shear walls non-compliant with current code provisions

This work forms part of a research programme to assess and strengthen existing reinforced concrete (RC) walls that were designed using older seismic codes. The main object of the present paper is to examine the behaviour of concrete shear walls that do not comply with modern seismic codes (Eurocode 2 (EC2) and Eurocode 8 (EC8)) and compare their experimental performance with the provisions for assessment of RC members included in EC8 Part 3. For this purpose, a series of six shear walls (height h = 1·40 m, length l = 0·74 m, thickness b = 0·10 m) was designed and tested under static cyclic loading. The wall specimens were characterised by various types of reinforcement arrangement, focusing on different amounts of shear reinforcement. The issues investigated are the failure modes, ductility level, the absence of confined boundary elements, the low amount of shear reinforcement, the influence of diagonal reinforcement and the influence of axial load. The experimental results are compared with the provisions included in EC8 Part 3, which predict the shear strength, the chord rotation ductility and the effective stiffness of RC shear walls.

Effect of confining of boundary elements of slender RC shear wall by FRP composites and stirrups

Existing concrete shear walls may be considered vulnerable for continuing service life due to changes in the seismic codes requirements, subjecting to intensive dynamic loads such as earthquake or explosion, and damages due to some local destructive loads. A review on the previous studies shows that despite the squat walls, very limited analytical and/or experimental studies have been already conducted on the FRP strengthening of slender RC shear walls under monotonic loading. In this paper the main focus is on the confinement of the boundary elements of shear walls with FRP composites and its effect on flexural behaviour of the wall. Nonlinear finite element analysis is performed on two shear wall specimens using damage plasticity model and considering tension stiffening effect. Results of the current study showed the superior effectiveness of strengthening FRP composite layers on ductile behaviour of concrete shear walls; i.e. the confinement of the boundary elements with FRP increased the ultimate displacement under almost constant load up to 50%. Furthermore, the results showed that it is sufficient to apply the FRP layers only on the boundary elements in the plastic hinge region of the wall.