Coupled Shear Walls Research Articles

Seismic behavior of precast concrete coupled shear walls with engineered cementitious composite (ECC) in the critical cast-in-place regions

The seismic performance of precast reinforced concrete (RC) coupled shear walls is significantly influenced by coupling beams and the beam-to-wall joints during large deformations into plastic ranges. This study investigated the use of engineered cementitious composite (ECC) in the cast-in-place beam-to-wall joints and the upper regions of the composite coupling beams as an innovative method to improve the seismic performance of precast RC coupled shear walls. Two 1/2-scale precast coupled shear walls were tested under reversed cyclic loading and seismic behavior in terms of failure characteristic, mechanical characteristic value, load-displacement hysteresis curves, load-displacement envelope relationship, stiffness degradation, ductility and energy dissipation capacity were evaluated. Research results show that the substitution of concrete with ECC in the critical cast-in-place regions proved to be an effective method to improve the seismic performance of the two-story spatial of precast RC coupled shear walls.

Analytical Study on the Dynamic Properties of Viscoelastically Coupled Shear Walls in High-Rise Buildings

AbstractAn innovative method of using viscoelastic (VE) dampers as coupling members between reinforced concrete shear walls has been recently developed for enhancing the wind performance and seismi...

A New Study of Seismic Behavior of Perforated Coupled Shear Walls

For years, coupled shear walls have been used in the mid-rise to-high-rise buildings as a part of lateral load resisting system, mostly because of their ability to control the displacement of structures. Recently, by changing the concept of design codes from strength-based to performance-based, assessment of nonlinear behavior of coupled walls became important for engineers. Therefore, many researchers now are looking for ways to improve and also predict the behavior of coupled walls under severe earthquakes. This paper presents the results of linear, nonlinear static (pushover), and nonlinear inelastic time-history analyses of a 10-story structure with two-dimensional coupled shear walls (CSW) which are perforated using three different patterns taken from considering the S22 stress of shell elements of shear walls. Nonlinear static analysis results confirm that perforation can increase the response modification factor of coupled walls up to 33 percent. In addition, the results of linear analysis and design indicate that perforation can reduce the required reinforcement of coupling beams and other frame’s structural components. In addition, results of nonlinear inelastic time-history analysis confirm that, using perforation patterns, the base shear—roof displacement hysteretic response improves and the systems with perforation patterns can absorb more energy under severe earthquakes.

STUDY ON SEISMIC PERFORMANCE OF HIGH DAMPING CONCRETE COUPLED SHEAR WALLS WITH CONCEALED STEEL PLATE BRACINGS

Quasi-static cyclic loading tests on two one-fourth scale models of four-story high damping concrete coupled shear walls (HDCSW) with concealed steel plate bracings are carried out, the bearing capacity, ductility, energy dissipation, and failure characteristics of the test models are analyzed systematically and are compared with those of HDCSW with mixed concealed bracings. Meanwhile, finite element analysis of HDCSW with concealed steel plate bracings under low-cycle load are conducted using the software ABAQUS. The results of numerical simulation and model experiments show that, compared with the HDCSW with mixed concealed bracings, the ultimate bearing capacity, the energy dissipation and the deformation capacity of the HDCSW with concealed steel plate bracings are improved; with decreasing span-depth ratio in the coupling beams, the HDCSW with concealed steel plate bracings show increasingly better seismic performance; when the steel ratios of wall limbs and coupling beams are less than 2.5% and 3%, respectively, the effect of the steel ratio on the ultimate bearing capacity of the HDCSW with concealed steel plate bracings is greater.

Performance-Based Seismic Design Of An Innovative HCW System With Shear Links based on IDA

Structural members yielding in shear are used in earthquake resistant systems, such as eccentrically braced steel frames and systems with passive energy dissipation devices, in a conscious effort to concentrate the energy dissipation capacity of the structure in components that can be repaired or replaced after a major earthquake. This paper presents an improved approach to a newly suggested design procedure of an innovative Hybrid Coupled Shear Wall (HCW) system consisting of a RC shear wall coupled with steel side columns via dissipative steel shear links. The primary design objective is to reduce or possibly avoid the damage in the RC wall while concentrating the seismic damage to the replaceable steel links which are shear critical, i.e. intended to fail in shear rather than flexure. To this purpose, a performance based approach is followed considering several limit states such as IO (Immediate Occupancy based on a limitation of the interstorey drifts), LS (Life Safety with yielding of the link, restoration possibilities of the links and limitation of the damages in the RC wall) and CP (near collapse situation with possible significant damages in the RC wall). The proposed design procedure is applied to several case studies which are analysed through nonlinear static and incremental dynamic analyses using finite element models in order to optimize the respective contribution of the wall, side columns as well as the links in terms of strength, stiffness and energy dissipation capacities.

Coupled Shear Wall with Fully Post-Tensioned Beams and Unbonded Reinforcing Bar at Toes

Coupled Shear Wall with Fully Post-Tensioned Beams and Unbonded Reinforcing Bar at Toes

병렬전단벽의 강도와 강성이 커플링보의 설계내력에 미치는 영향

본 연구에서는 초고층건물의 횡력저항 구조형식으로 널리 사용되는 병렬전단벽-커플링보 구조시스템에서 전단벽의 강도, 강성이 커플링보의 설계 강도에 미치는 영향을 분석하였다. 커플링보에 발생하는 설계내력은 코어벽체의 두께와 콘크리트의 강도가 변하더라도 층별 설계내력은 유사한 경향을 보이고 있으며, 벽체 콘크리트 강도와 두께에 따라 커플링보에 발생하는 외력은 다소 감소하는 경향이 있다. 커플링보의 설계내력은 6개 모델 전부 40층 건물에서, 10층에서 15층의 범위에서 가장 높게 발생하고 있음을 알 수 있다. 즉, 병렬전단벽의 휨변형 변곡점이 형성되는 건물높이의 0.25H~0.375H 위치에서 최대 부재력이 발생한다. 벽체두께가 증가 할수록 코어내부의 커플링보의 발생 외력은 점차 증가하는 것으로 확인되었다. 또한 벽체 두께가 두꺼워질수록 벽체의 콘크리트 강도 증가에 따른 커플링보의 부재력 변화는 적게 나타나는데, 이는 벽체 두께가 두꺼우므로 콘크리트 강도변화의 영향이 적게 미치는 것으로 분석된다. 병렬전단벽의 두께증가는 콘크리트의 강도증가보다 강성변화에 큰 영향을 미치고, 이에 따라 커플링보의 부재력 변화에도 더 큰 영향을 미치는 것으로 분석된다. In this research, the effects of the strength and stiffness of shear walls on the design strength of coupling beams are studied in the shear wall-coupling beam structural system widely used as the lateral-drift resistant system of high-rise buildings. The results show that the design strength of the coupling beams decreases with decreasing concrete strength and core wall thickness, but the shape remains unchanged. In all six models, the design strength of the coupling beams has the largest value at the 10~15th floors in a 40-story building. In other words, the design strength of the coupling beams has the largest value at 0.25H~0.375H where the inflection point exists. The thicker the walls, the smaller the change in the member forces. The thickness of the coupled shear walls has more influence on the design strength of the coupling beams than the concrete strength.

Investigation of Stiffness Effect of Coupling Beam on Boundary Element Detailing in Structures with Hybrid Coupled Shear Walls

Coupled walls are known to be efficient lateral load-bearing systems. Coupling beam and wall piers are two important and effective elements in the general response of these structures. In this paper, stiffness effect of steel coupling beams on boundary elements in coupled shear walls has been investigated. The provisions of Iranian National Building Code for concrete structure (INBC-No. 9) for evaluating detailing requirements at wall boundaries are based on studies on uncoupled continuous walls, in which stress distribution across sections is assumed to be linear and in un-cracked sections. Due to the fact that there have been severe axial forces on wall piers resulting in the creation of cracks in sections of tension walls, the applicability of these provisions in coupled walls should be evaluated. Several coupled wall structures with different geometrical specifications, representative of various ratios of stiffness of the coupling beam to stiffness of the wall (RSBW), under equivalent lateral force, were designed, and efficiency of the code provisions was investigated in comparison with the results of the numerical analysis in Abaqus software. In this analysis, nonlinear behavior of material was considered. Results show that for structures with large and medium RSBW, code provisions are not appropriate in evaluating detailing requirements of tension wall boundaries, and a nonlinear stress distribution on the section should be used. For compression walls and structures with low RSBW, code provision is reliable.

Shear capacity of steel fibre reinforced concrete coupling beams using conventional reinforcements

The seismic performance of coupled shear wall systems is governed by the shear resistance of their coupling beams. Steel fibre reinforced concrete (SFRC) is widely applied in coupling beams for its positive contribution to their ductility. This study deals with the seismic behaviour of SFRC coupling beams using conventional reinforcements and develops a simplified model that applies the Mohr-coulomb failure criterion to predict the seismic shear strength of SFRC coupling beams. Variables studied include concrete compressive strength, fibre volume fraction and span-to-depth ratio. Results show that steel fibres improve the shear strength, deformation and energy dissipation capacity of the SFRC coupling beams. When fibre volume fraction is greater than 2.5% or span-to-depth ratio excesses 2.5, SFRC coupling beams present an excellent seismic performance and avoid effectively brittle shear failure. Using the Mohr-Coulomb failure criterion, a simplified shear model was proposed for SFRC coupling beams and presents a good accuracy and reliability. Furthermore, taking into account the negative effect of span-to-depth ratio, the proposed shear model was modified further. The comparative results demonstrated that the new shear model presents a more reasonable assessment accuracy and higher reliability.

Structural performance of corrugated web steel coupling beams

In lateral force resisting systems, the structural behaviour and seismic performance of coupled shear walls depends on the coupling beams. Steel coupling beams are considered to be an efficient alternative to reinforced concrete coupling beams, and improve the ductility and performance of the coupled shear wall system. This paper considers the application of corrugated webs as an alternative to flat webs having stiffeners. Finite-element models are described and used to investigate the effect of changes to the shape of the web-plate; flat, trapezoidal, curved and zigzag patterns are considered as well as the thickness, number of corrugations and corrugation angle. The effect of these parameters on the structural performance of the coupling beams is determined under both monotonic and cyclic loadings. Results of pushover analyses show that the use of corrugated webs instead of stiffened flat webs can improve the rotation capacity of steel coupling beams and cyclic analyses show the high performance of the corrugated web steel coupling beams in dissipating energy. Furthermore, it is shown that the rotation capacity and energy dissipation capabilities of steel coupling beams are sensitive to corrugation parameters.

Cyclic Behavior of Replaceable Steel Coupling Beams

For improving the seismic resiliency of coupled shear wall systems, a type of replaceable steel coupling beam was developed, which consists of a central “fuse” shear link connecting to steel beam segments at its two ends. Inelastic deformation is concentrated in the shear link during a severe earthquake, and the damaged links can be replaced easily as specialized link-to-beam connections are adopted. This paper presents a series of quasi-static tests conducted to examine the seismic behavior and replaceability of the replaceable coupling beams. A total of four large-scale specimens were designed and tested, where different types of beam-to-link connections were adopted, including end plate, splice plate, bolted web, and adhesive web. All specimens fully developed the shear strength of the fuse links and showed large inelastic rotation capacity of no less than 0.06 rad, except for the specimen with the adhesive web connection, which failed at an early stage. The specimen with the end plate connection had inelastic deformation concentrated in the shear link, showing very stable hysteresis behavior. Slippage of high-strength bolts was observed at the splice plate and bolted web connections, which led to increased deformation and “pinching” in hysteresis loops of coupling beams. Interestingly, at a coupling beam rotation exceeding 0.01 rad, a large axial force developed in the steel coupling beams, the maximum value of which reached approximately a quarter to half of the axial yield strength of the shear link. In addition, on-site replacement of shear links was demonstrated after the coupling beam specimens experienced 0.02-rad rotation. The end plate connection was replaced within the shortest time, whereas the bolted web connection was able to accommodate the largest residual deformation.

Structural Shear Wall Systems with Metal Energy Dissipation Mechanism

Shear wall structures have been widely used in high-rise buildings during the past decades, mainly due to their good overall performance, large lateral stiffness, and high load-carrying capacity. However, traditional reinforced concrete wall structures are prone to brittle failure under seismic actions. In order to improve the seismic behavior of traditional shear walls, this paper presents three different metal energy-dissipation shear wall systems, including coupled shear wall with energy-dissipating steel link beams, frame with buckling-restrained steel plate shear wall structure, and coupled shear wall with buckling-restrained steel plate shear wall. Constructional details, experimental studies, and calculation analyses are also introduced in this paper.

Analysis of Coupled RC Shear/Core Walls by Macro Model

A modified macro numerical model for coupled RC shear/core walls is proposed to better consider the deformation compatibility between the coupling beam and the wall element and to incorporate the out-of-plane effect of the wall panel. In this model, the three-dimensional macro shear wall element model with distributed shear springs and out-of-plane freedom is adopted to simulate the wall unit; a one-dimensional line element consisting of three sub-units in series based on the vertical deformation compatibility is adopted to simulate the coupling beam. The case study shows that a numerical model based on the vertical deformation compatibility results in more accurate simulation of the mechanical behavior of the RC coupled shear wall. The modified model developed in this study has the advantages of fast calculation and high precision, which makes the model appropriate for engineering application.

An enhanced component based model for steel connection in a hybrid coupled shear wall structure: Development, calibration and experimental validation

In the present paper the development, calibration and experimental validation of two component-based models of dissipative steel links connecting a reinforced concrete wall to a steel gravity frame is presented.The dissipative capacity of such structures is greatly influenced by the effective hysteretic behavior of the wall-to-column coupling system. Within the present work, experimental tests results on two different configurations of wall-to-column coupling system are presented. The development and calibration of two non-linear cyclic component-based models, one for each configuration, are described, allowing a better understanding of the force transmission mechanisms and their influence on the global structural behavior.

Effectiveness of the shape memory alloy reinforcement in concrete coupled shear walls

The use of shape memory alloys as a rebar in concrete structures has been receiving increasing attention among researchers. In this study, it is intended to evaluate the application of superelastic Nitinol in reducing the damage to the coupling beams and opening corners within a concrete shear wall. Abaqus finite element software was utilized to develop three verified coupled shear wall models. First, a model without diagonal and shape memory alloy rebars is developed to assess conventional shear walls with openings. Steel diagonal rebars are embedded in the coupling beams of the second model, and shape memory alloy diagonal rebars are embedded in the coupling beams of the third model. Shape memory alloy is also implemented in the opening corners of the third model. All models are subjected to cyclic loading to evaluate the concrete damage. Results indicated that the diagonal rebars reduced damage to the coupling beam and opening corners. The damages were the least when shape memory alloy diagonal rebars are utilized in the model. The superelastic behavior of the shape memory alloy also reduced permanent displacement of the shear wall subjected to substantial lateral loadings.

Experimental study on the seismic behavior of coupled shear wall with concealed partitioned steel plates

To study the seismic behavior and post-earthquake repairability of coupled shear wall with concrete filled steel tube (CFST) frame and concealed partitioned steel plates (SPs), three 1/5 scaled coupled shear wall specimens were designed with different type of CFST column or core structure. Low-cycle reversed loading was adopted in the test. The test contained two stages. Load-carrying capacity, energy dissipation, ductility, stiffness and failure characteristic of the specimens were compared in pre-repair stages and post-repair stages. The conclusions are drawn that the core structure shows a good ductile yielding mechanism. The cross-section type of frame has an obvious effect on the seismic behavior of shear wall. After damage and strengthening, the new coupled shear wall still has enough seismic capacity and good energy dissipation capacity, and it is easy to be repaired after earthquake. Finite element analysis software ABAQUS has been used to simulate the behavior of coupled shear wall. Ultimate strength is obtained with the vibration of thickness of SPs.

The Effect of Spandrel Beam's Specification on Response Modification Factor of Concrete Coupled Shear Walls

Response modification factor (R factor) is one of the seismic design parameters to be considered in evaluating the performance of buildings during strong motions. This paper has tried to evaluate the response modification factor of concrete coupled shear wall structures with various length/depth ratios of spandrel beams. The effect of diagonal reinforcement of spandrel beam was also evaluated on the R factor. The R factor directly depends on overstrength factor and ductility reduction factor. For this purpose, three conventional structures with 5, 10 and 15 story buildings (having various spandrel beam's length/depth ratio with and without diagonal reinforcement) were selected and the nonlinear static analyses were conducted to evaluate their overstrength and ductility reduction factors. Also for a 5-story structure, nonlinear dynamic analysis (time history) was carried out in order to compare the results with nonlinear static analysis. It was concluded that the R factors using nonlinear time history analysis and nonlinear static analysis are almost the same. The results also indicate that by increasing the height of the structure, the overstrength reduction factor decreases; while the ductility reduction factor increases. Also, the response modification factor decreases with increasing length/depth ratio of spandrel beams. The coupled shear walls with diagonal reinforcement in spandrel beams have a greater R factor.

완화된 배근 상세를 갖는 병렬전단벽 구조시스템의 내진성능평가

완화된 배근 상세를 갖는 병렬전단벽 구조시스템의 내진성능평가

Experimental study of a replaceable steel coupling beam with an end-plate connection

In order to enhance the post-damage repair capability of the hybrid coupled shear wall systems, a different type of replaceable steel coupling beam with end-plate connection was investigated. Different from conventional configurations, the coupling beams were not embedded into the walls to minimize the post-event repair/replacement difficulties and expenses. To assess the seismic behavior and post-damage replaceability of the coupling beam, a two-stage experimental program was performed to test the full-scale specimens, each utilizing coupling beams with different strength and stiffness. The results of the first specimen indicated a ductile failure with a concentration of inelastic deformation at steel web and thus exhibited desirable deformation and energy absorption capacities with minimum damages to the shear wall. Again, on the minimum repaired wall-pier, the second specimen via the proposed connection, with improved characteristics such as strength and stiffness, was installed and tested. The results demonstrated excellent stiffness, strength, and ductility characteristics of subassemblages under cyclic loading, with considerable energy dissipation concentrated in the coupling beam web. Although the second specimen failed from the threaded area of the tensile bolts, due to increased coupling beam strength, the specimens were able to sustain large nonlinear displacements without significant damage in the connection to the wall pier regions; representing that this connection configuration would require little repair, if any, after a severe earthquake.

Investigation of the effects of viscous damping mechanisms on structural characteristics in coupled shear walls

This study addresses energy dissipation mechanisms to investigate the effects of the internal and external viscous damping on structural characteristics in coupled shear walls. A discrete Reference Beam (RB) is firstly proposed and a Distributed Internal Viscous Damping (DIVD), composed by bending and shear mechanisms, is defined. Meanwhile, the linear classical damping is considered. A low-order finite element method (FEM) is adopted for lateral analyses. For the sake of simplicity, a Generalized Sandwich Beam (GSB) is then developed through the replacement of the set of connecting beams of the RB by an equivalent elastic and dissipative core and a FEM is employed for its dynamic analysis. The passive damping modeling through the GSB is presented using continuous models. Concerning slender structures, the GSB is reduced to a Coupled Two-Beam (CTB) including the damping effects. The analytical solution of the CTB is presented to be a benchmark for the FE solutions. The validity of both numerical and analytical solutions is confirmed via numerical examples. The effectiveness of proposed damping models on dynamical responses and vibration characteristics are tested with respect to continuum-based controlling parameters, and a qualitative model is consequently proposed to appropriately choose the damping mechanisms depending upon the parameters of coupled shear walls. The suitability of various damping models is finally compared to current damping predictors and full-scale measured data given for RC buildings. The results reveal that the bending and shear damping are somehow efficient where the linear classical damping is incapable to be always a proper mechanism.