RC Shear Walls Research Articles

Experimental testing of RC shear wall seismic retrofit using selective weakening, self-centering and Ultra High performance concrete

Traditional retrofit methods often focus on increasing the structure's strength, stiffness, or both. This may increase seismic demand on the structure and could lead to irreparable damage during a seismic event. This paper presents a retrofit method, integrating concepts of selective weakening and self-centering (rocking) to achieve low seismic damage for non-code compliant reinforced concrete shear walls. The proposed method involves converting traditional cast-in-place concrete shear walls into rocking walls, which helps to lower the shear demand, while allowing re-centering. Two large-scale lateral load tests were performed to validate the retrofit concept on a concrete shear wall designed according to pre-1970s standards. The design parameters investigated were amount of energy dissipating reinforcements and confinement enhancement. Two different methods using Ultra High Performance Concrete (UHPC) were investigated to provide additional confinement to boundary elements of older shear walls. Observations from the tests showed minimized damage and enhanced recentering in the retrofitted wall specimens. Use of UHPC in the boundary elements of the retrofitted walls provided additional confinement and reduced damage in the rocking corners.

A Numerical Study on the Seismic Performance of a Horizontal Dry Connection for Precast Concrete Shear Walls

Dry connections primarily consist of high-strength bolts and steel plates. They are commonly used in precast structures as they maximise time efficiency in the assembly stage compared with conventional methods. In this study, an embedded horizontal dry connection was developed using a square-shaped ring connector, high-strength hex nuts and flat washers, and grout for assembling precast concrete shear walls. Using Abaqus CAE 6.14, a numerical study was conducted on two full-scale RC shear walls including one monolithic and one precast specimen to assess the seismic performance of the bolted connection under the combined effect of axial and fully reversed cyclic loading. The average displacement ductility ratio of the precast specimen integrating the bolted connection was three times as much as the reference specimen. However, its relative energy dissipation capacity and shear strength were 21.94% and 27.92% lower, respectively. A parametric study was also carried out on the thickness and grade of the ring connector, grade of the vertical steel bars, number of ring connectors, and diameter of the vertical steel bars at the connection joints. Results showed that the seismic performance of the bolted connection was highly dependent on the bar diameter and number of ring connectors.

Seismic performance evaluation of steel and GFRP reinforced concrete shear walls at high temperature

Fire-induced structural damage to the seismic performance of reinforced concrete shear walls is critical in the event of a fire-earthquake scenario. However, only few researchers have studied the seismic performance of reinforced concrete shear walls at high temperatures. This study focuses on the seismic performance of fiber reinforced concrete shear walls at high temperatures by using finite element (FE) software, ABAQUS. The experimental test available in a literature on seismic behavior of shear walls exposed to fire and thermal properties of glass fiber reinforced polymer (GFRP) bars were used to validate the FE model and showed good agreement and thus used in the simulation.The FE results showed that exposure of RC shear wall to fire reduced the strength of the wall. The strength of walls at the maximum applied drift of 3.2% with concrete cover thicknesses of 20 mm, 25 mm, and 30 mm was dropped by about 70%, 76%, and 85% of the reference shear wall, respectively. Similarly, the strength of RC walls was reduced by about 80%, 75%, and 68% of the reference shear wall for the duration of fire exposure of 30 min, 60 min, and 120 min, respectively. Additionally, the strength of walls due to one side, two sides, or all sides’ exposure to fire was decreased by about 68%, 56%, and 50% of the reference shear wall, respectively. It can generally be concluded that the fire exposure sides has largely affected the strength of the shear wall compared to the other parameters and GFRP bars were more sensitive to temperature than steel bars.

Experimental and numerical investigation on the seismic behaviors of RC shear walls with multiple post-openings before and after strengthening by steel plates

In this paper, the quasi-static tests of seven RC shear walls and the corresponding finite element simulations were carried out to investigate the seismic behaviors of the RC shear walls with multiple post-openings before and after being strengthened by bonding steel plates, including failure modes, bearing capacities, ductility, energy dissipation capacities, structural performance levels, and also the strain distribution of the rebars. The detail arrangements of the post-construction openings are taken into account, on the premise of the same total area of the openings. Not only in the tests but also in the simulations, there is one RC wall with a single post-opening in the center of the wall, one RC wall with two post-openings that are horizontally arranged at the mid-height of the wall, and one RC wall with two post-openings which are vertically arranged at the mid-length of the wall. In addition, other three specimens, with the same opening arrangements as the three types of RC walls motioned above, strengthened by bonding steel plates around the openings, and one shear wall without openings for reference were fabricated. The results showed that the failure modes of reinforced or unreinforced RC shear walls with post-openings are shear failure and flexural shear failure respectively. The seismic bearing capacities of the shear walls with post-openings can be obviously recovered, up to 33.5%, by bonding steel plates. Moreover, the ductility coefficients of those strengthened RC walls were also improved, in the range of 5.6% to 58.1%.

Review of existing empirical models for blast loading parameters, and dynamic response prediction of RC shear wall under spherical free-air and hemispherical surface blasts

Review of existing empirical models for blast loading parameters, and dynamic response prediction of RC shear wall under spherical free-air and hemispherical surface blasts

FINITE ELEMENT ANALYSIS ON THE NONLINEAR BEHAVIOR OF THE RC SHEAR WALL WITH REGULAR OPENINGS INFLUENCED BY HIGH-STRENGTH STEEL

This paper presented a nonlinear finite element analysis of lateral loading RC shear walls with regular openings using the 3D-NLFEA program. The RC shear walls model was generated from the available test results in the literature. To model the concrete under a complex stress state, a multi-surface plasticity model which combines compression failure surface with tension cut-off failure surface was used. The model was intended to look at the load-displacement relationship and the crack pattern between the model and the numerical model. In addition to the numerical model verification, parametric studies were carried out to investigate the use of high-strength steel (HSS) of the two different grades (grades 100 and 120) to replace all the normal-strength steel (NSS) or only some of it. The parametric studies found that the shear wall with the NSS bar demonstrated higher stiffness and achieved higher lateral load with the lowest extent of damage (compared to the RC shear wall with the HSS bar). On the other hand, using the HSS bar resulted in lower stiffness, lower lateral load, and higher damage region, which was expected as more strain is required to yield the HSS bar.

Effect of the Size of Multiple Perforations on the Performance of Long Reinforced Concrete Shear Walls

This paper investigates the effect of the size of multiple openings on the behavior of shear walls. In this study, the wall span is 24 m, the wall depth is 4 m, and is 0.3 m thick. The work involves the discussion of the three main kinematic and strength indicators that influence the shear wall performance. They are the load displacement relationship for the wall top edge, the equivalent concrete stress flow within the body of the wall, and the bending stress gradient at the bottom of the wall. The wall is constructed of reinforced concrete. A nonlinear finite element push over analysis has been carried out using Ansys software. The element Solid65 presented by Ansys effectively simulates the true behavior of concrete. The steel reinforcement has been modeled by link180 element. Primarily a finite element model for the solid bearing RC shear wall has been constructed and analyzed. The primary step has involved calibration and validation of the finite element model. Thereafter, pushover analysis has been performed for four perforated walls of various opening sizes. The study has indicated that when the percentage of the sum of the perforations’ areas to the total wall area surpasses 8.35%, the shear wall load carrying capacity starts to degrade. When the percentage of the sum of perforations surpasses 16.7% of the total wall area, the shear wall behavior starts to convert to that of two coupled shear walls. The larger the opening size is, the higher the stresses are, and the less the wall load carrying capacity is. When the percentage of the sum of the perforations’ areas to the wall total area surpasses 25%, the behavior of the shear wall converts to that of a frame. The study recommends that further future studies should be carried out on the effect of providing CFRP sheets on the edges of the openings, especially at lower stories in order to control concrete cracks at the edges of the perforations resulting from the developed large concrete equivalent stresses.

Anti-collapse performance of concrete-filled steel tubular composite frame with RC shear walls under middle column removal

In this study, the anti-collapse performance of a 1/4 scaled two-story two-bay concrete-filled steel tubular (CFST) composite frame with RC shear walls was experimentally and numerically studied in the scenario of middle column loss through the quasi-static loading method. Test results show that the main failure modes of the specimen were the fracture and local buckling of steel beams, and the concrete crush in the shear walls and the slabs near the failure column. After the steel beam failed, the internal force was transmitted from the steel beams to the CFST columns and shear walls. Based on the refined finite element models, the effects of the column failure positions, limb lengths, reinforcement ratios, and types of shear walls on the collapse resistance of the models were analyzed. Simulation results indicate that the shear wall significantly contributes to resisting vertical load in the initial loading stage. In the large deformation stage, the collapse resistance of the specimen is mainly provided by the sub-framed structure. After the limb length of the shear wall exceeds 2/3 span, the increase in the bearing capacity is not obvious, while the failure displacement is significantly decreased. The reasonable reinforcement ratio of the RC shear wall in the structure should be designed in the range of 0.2%–5%. The local reinforcement methods for the collapse resistance of CFST composite frame with RC shear walls were proposed. In addition, the simplified dynamic analysis and dynamic increase factor (DIF) for the CFST composite frame with RC shear walls were analytically studied by energy balanced method.

Experimental Investigation on the Cyclic In-Plane Behavior of GFRP-Reinforced Concrete Shear Walls

The current study presents an experimental investigation performed on slender reinforced concrete shear walls, representing a common lateral-load resisting system of mid-rise buildings. The walls were reinforced with steel and glass fiber-reinforced polymer (GFRP) bars and tested up to failure under reversed quasi-static cyclic loading to investigate the capability of GFRP bars in reinforcing RC shear walls under seismic loads. Moreover, the effect of the GFRP reinforcement ratio on the structural response, deformation performance, and failure mode resulting in RC walls, compared with its behavior when reinforced with steel bars, is also investigated. Six full-scale shear walls with an aspect ratio of 3.25 were constructed. The reference wall was entirely reinforced with steel bars. Two specimens were reinforced by hybrid scheme of GFRP–steel bars. The remaining three shear walls were entirely reinforced with GFRP bars. The overall performance of each wall was characterized by investigating the lateral load capacity, hysteretic response, cracks propagation, ductility, and the behavior of energy dissipation. The experimental results showed that GFRP-reinforced concrete walls had an elastic behavior characterized by a stable hysteretic response with recoverable deformation of more than 80% of the ultimate load. However, sudden and brittle failure was attained for the wall with a high GFRP reinforcement ratio. GFRP decreases the displacement ductility of the shear walls by an average of 32.9%, depending on the reinforcement ratio, compared to that reinforced by steel bars. Moreover, lower energy dissipation through inelastic deformation was obtained for the walls reinforced with GFRP bars. Nonetheless, when GFRP bars are combined with steel bars, acceptable levels of dissipated energy are attained compared to the steel-reinforced wall.

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.

Influence of the tension shift effect on the force–displacement curve of reinforced concrete shear walls

A precise calculation of the inelastic force–displacement curve of shear walls up to the ultimate load is important for several reasons. The curve is needed for the capacity curve, ductility or behaviour coefficient in an earthquake analysis. Using the pure moment–curvature curve from the section analysis underestimates the deformation capacity of walls significantly. The tension shift effect caused by the diagonal cracks under shear force is missing. This effect can become larger than the flexural deformations. This contribution investigates the influence of the tension shift on the load–displacement curve of RC shear walls. A reliable model is introduced and the influence of axial load, reinforcement ratio and aspect ratio of the wall on the tension shift is studied. The model is validated on four shear wall tests, taken from the literature. Good accordance compared to the experimental results could be achieved.

Hysteretic Performance of Hybrid GFRP-Steel Reinforced Concrete Shear Walls: An Experimental Investigation

The vulnerability of steel reinforcement to corrosion is a severe problem affecting the overall performance and durability of concrete structures in aggressive environments. The interest in using alternative Glass fibre-reinforced polymer (GFRP) bars lies in their corrosion resistance and higher tensile strength-to-weight ratio. Nevertheless, experimental results on the seismic behaviour of GFRP-reinforced walls are scarce. This paper investigates the hysteretic performance of hybrid steel-GFRP reinforced concrete shear walls to provide valuable experimental evidence for such walls under seismic loading. Six RC shear walls with steel and GFRP reinforcement were tested under pseudo-static reversed-cyclic lateral load. Three shear walls were reinforced by GFRP bars as longitudinal and transversal reinforcement, and two walls were reinforced with hybrid GFRP-steel bars with different ratios of web reinforcement. A reference specimen, ordinary steel-RC shear walls, was also introduced to certify the capability of GFRP as reinforcement bars. The results indicated that the GFRP-reinforced concrete slender walls had a stable hysteretic response and slight residual drift up to failure. Lower residual deformations, higher displacement capacity, and increased lateral strength could be observed with the GFRP web reinforcement ratio increase. Moreover, the fundamental period of GFRP and hybrid GFRP-steel reinforced walls can reach more than twice its original value prior to failure.

Machine learning-based predictive models for equivalent damping ratio of RC shear walls

Energy-based seismic design is being rapidly developed and suggests that the seismic demands are met by the energy dissipation capacity of the structural members. Equivalent damping ratio is a measure of energy dissipation in structural members that accounts for the post-elastic behavior of the member and provides insight regarding the dynamic response reduction during a seismic event. The present study implements a machine learning algorithm to estimate the equivalent damping ratio in reinforced concrete shear walls at displacements corresponding to a 1.0% lateral drift ratio. Five different machine learning models, namely, Robust Linear Regression, K-Nearest Neighbor Regression, Kernel Ridge Regression, Support Vector Regression, and Gaussian process regression were evaluated in order to choose the model with the highest accuracy. Among all models, Gaussian process regression, a machine learning method with successful implementation experiences in civil/structural engineering related problems, is selected to identify the equivalent damping ratio. The developed GPR-based algorithm uses a database of 161 rectangular shear walls subjected to quasi-static reversed cyclic loading with geometry and mechanical properties commonly found in building stocks of many earthquake-prone countries. The proposed algorithm estimates the equivalent damping ratio for each specimen by predicting the cyclic dissipated energy and lateral force values as two dependent variables. The model validation results show a mean coefficient of determination (R2) of about 0.89; a relative root mean square error of about 0.14 and a mean absolute percentage error of 10.44%, which is considered a substantially accurate prediction for such a complex problem. An open-source model and the entire database are provided which can be used by researchers and also design engineers. The proposed predictive model enables comparing the damping capacity of shear walls and the outcomes of this study are believed to contribute to the energy-based design or performance evaluation procedures in terms of predicting the energy capacity of shear walls.

Seismic performance of flexure-dominated reinforced-engineered cementitious composites coupled shear wall

The feasibility of using engineered cementitious composites (ECC) to improve the seismic performance of coupled shear walls was investigated experimentally and analytically. Reinforced-ECC (RECC) coupled shear wall was tested under cyclic loading for comparative study with its RC counterparts. Important seismic performance indicators, such as the deformation mode, damage pattern, stiffness, ductility and energy dissipation of the two coupled shear walls were compared and analyzed. The RECC shear walls and RC shear walls exhibited flexural failure modes with different damage patterns. The damage was concentrated mainly in the plastic hinge area, which include the bottom of the wall and the ends of the coupling beams. The RECC shear wall exhibited smeared cracking characteristics with a significantly smaller crack width. The RECC members showed ductile failure mode without crushing or spalling, and provided effective restraint to the longitudinal rebar, which delayed the buckling of the longitudinal rebar. The deformation capacity of the RECC shear wall was twice that of the RC shear wall, and the energy dissipation capacity of RECC shear wall also improved significantly compare to RC shear wall. The RECC shear wall exhibited a slightly higher load-bearing capacity compared with its RC counterpart. The ultimate strength of the RECC and RC coupled shear walls were estimated based on the compression–bending mechanism. The calculated results agreed well with the test results. The estimated yield and ultimate displacement of the RECC and RC shear walls were close to the test results.

Machine learning-based estimation of energy dissipation capacity of RC shear walls

In current practice, the seismic design of reinforced concrete shear walls primarily relies on the wall shear strength as well as proper reinforcement detailing to ensure sufficient ductility. However, experimental results have shown that the seismic (input) demands are met by the energy dissipation capacity in the structural members; therefore, the influence of hysteretic behavior on seismic behavior is considerable. An energy-based approach that reflects the effect of repeated loads in seismic performance – which is typically neglected in the seismic codes – would serve as a supplemental index in the design process. With this motivation, a predictive model is proposed to estimate the energy dissipation capacity of reinforced concrete shear walls. A comprehensive database consisting of 312 shear walls tested under cyclic loading and a widely used and powerful machine learning method, namely Gaussian Process Regression (GPR), is used to investigate the effects of wall design parameters (e.g. wall geometry, reinforcement details) on energy dissipation capacity and to develop the predictive model as a function of such parameters. Eighteen design parameters are shown to influence the energy dissipation, the most important of which are identified by applying sequential backward elimination and feature selection methods. The ability of the proposed model to make robust and accurate predictions is validated based on unused data with a prediction accuracy (the ratio of predicted/actual values) of around 1.00 and a coefficient of determination (R2) of 0.93. The outcomes of this study are believed to contribute to the wall design process by (i) defining the most influential wall properties on the seismic energy dissipation capacity of shear walls and (ii) providing predictive models that can enable comparisons of different wall design configurations to achieve higher energy dissipation capacity.

Impact of Revised Seismic Hazard Values in NBCC 2015 on RC Shear Wall Buildings

Impact of Revised Seismic Hazard Values in NBCC 2015 on RC Shear Wall Buildings

A Comprehensive Study on the Effect of Regular and Staggered Openings on the Seismic Performance of Shear Walls

Shear walls have high strength and stiffness, which could be used at the same time to resist large horizontal loads and weight loads, making them pretty beneficial in several structural engineering applications. The shear walls could be included with openings, such as doors and windows, for relevant functional requirements. In the current study, a building of G + 13 stories with RC shear walls with and without openings has been investigated using ETABS Software. The seismic analysis is carried out for the determination of parameters like shear forces, drift, base shear, and story displacement for numerous models. The regular and staggered openings of the shear wall have been considered variables in the models. The dynamic analysis is carried out with the help of ETABS software. It has been observed that shear walls without openings models perform better than other models, and this is in agreement with the previous studies published in this area. This investigation also shows that the seismic behaviour of the shear wall with regular openings provides a close result to the shear wall with staggered openings. At the roof, the displacement of the model with regular openings was 38.99 mm and approximately 39.163 mm for the model with staggered openings. However, the model without a shear wall experienced a displacement of about 56 mm at the roof. Generally, it can be concluded that the openings have a substantial effect on the seismic behaviour of the shear wall, and that should be taken into consideration during the construction design. However, the type of opening (regular or staggered) has a slight effect on the behaviour of shear walls.

Seismic performance of a novel partly precast RC shear wall with double precast edge members and a central T-shape CIP member

A novel partly precast shear wall was proposed in this study to accelerate construction and further reduce the weight of precast components for high-rise building structures. The proposed wall consisted of double precast edge members and a central cast-in-place (CIP) member. The rebar splice was achieved by the grout-filled sleeve connection for the precast members and lap splice connection for the CIP member. The seismic performance of the proposed wall was investigated through a full-scale experimental program, in which three specimens were designed and tested under the combination of a constant axial load and cyclic loads, including two identical proposed walls and a CIP wall as a reference. The axial load was applied to achieve a high axial load ratio of 0.5. Based on the test results, it was found that the proposed walls were subjected to similar damage progression and failure mode with the CIP wall. All failed due to concrete crushing, shear cracking and rebar buckling at the base corners of walls. The only difference was that the proposed walls would experience additional vertical cracks along the interface between the precast and CIP zones due to insufficient bond strength between at the interface. It was also found that under the high axial ratio of 0.5, the proposed walls would have comparable seismic performance with the CIP wall in terms of deformability, ductility and lateral load capacity. In addition, the two identical proposed wall had similar seismic performance indicating the good repeatability of test data and stable performance of the walls. Therefore, the proposed walls can have satisfactory seismic performance during a seismic event and could be an effective alternative method for the CIP walls if designed appropriately.

Effects of Tsunami Forces on RC Framed Structure Subjected to Bracing and Shear Wall

Abstract— The Indian Ocean Tsunami on 26 December 2004 resulted into massive destruction to coastal communities with more than 3,00,000 people losing their lives, and causes severe damage to buildings, bridges and other infrastructure. Such catastrophic event made the coastal community realize the need for the preparedness against initial ground shaking and subsequent effects followed by Tsunami. The current study focuses on progressive collapse analysis of 10 storey reinforced concrete frame with bracing and shear wall subjected to different Tsunami forces. The Tsunami forces were calculated according to the guidelines of FEMA P-646, ASCE 7-16. The December 26, 2004 Tsunami parameters on the coast of Tamilnadu were considered for the evaluation of effect of Tsunami forces on structure. To simulate similar conditions structure was designed according to Zone-III and was subjected to Tsunami forces for the 12m, 9m and 6m runup. This study consists of two parts: 1) The calculation of Tsunami forces and application of forces on structure and 2) Progressive collapse analysis of structure by removing the vertical load bearing critical members due to Tsunami forces. The progressive collapse analysis was carried out with the help of commercially available software named ETABs 16. The critical members were removed. The analysis was carried out by referring General Services Administration (GSA-2013, Revised 2016) and Unified Facility Criteria - Department of Defense (UFC - DoD-2009, Revised 2016) guidelines. From the analysis results it was found out that structure becomes critical when Bracing and Shear wall were oriented normal to the flow of tsunami. Upon performing the progressive collapse analysis of structure which was found to be critical due to Tsunami forces reveals that the joint at which the vertical member was removed did not exceed the acceptance criteria of collapse prevention. Hence structure was able to redistribute the unbalanced gravity load and thus prevents the progressive collapse of structure. Keywords— RC Frame, Shear wall and Bracing, Tsunami Forces, Nonlinear Static Analysis, Progressive Collapse

Response of nonconforming RC shear walls with smooth bars under quasi-static cyclic loading

In this study, an experimental investigation is conducted to determine the behavior of RC shear walls found in old and existing buildings that do not comply with the design rules in modern earthquake standards. Scaled reinforced concrete shear wall specimens are built with smooth bars and low concrete quality. The dimensions of the shear wall specimens were selected with an aspect ratio bigger than two as 2500, 1050, and 150 mm for the height, length, and thickness, respectively. Four specimens are representative of nonconforming shear walls, and one wall is used as a reference specimen which was designed in accordance with recent building codes using deformed bars. The behavior of the shear walls is determined experimentally by displacement-lateral load relationship under lateral cyclic loading. The study used measurable parameters to investigate the behavior of the test specimens in terms of lateral force capacity, rigidity, ductility, dissipated energy, and displacement components contribution to the total lateral response of the walls. The results showed a substantial loss of stiffness, ductility and energy dissipation capabilities for the tested nonconforming shear walls. Moreover, it is proven in this study that these specimens are governed by the bar slip phenomena which demonstrated more than 80% contribution to the total lateral displacement capacity. In contrast, the reference shear wall exhibited a notable flexural behavior and plastic hinge formation. Additionally, the shear walls built with smooth reinforcement bars lost about 44% of their theoretical potential flexural capacity due to the observed bar slip failure.