Coupled Shear Walls Research Articles

A general simplified method for static and free vibration analysis of coupled shear walls of a bay

In recent years, coupled shear walls have been used more often because they provide a significant percentage of the total stiffness of a tall building total horizontal bracing system. This article presents an analytical procedure for the static and dynamic analysis of coupled shear walls of a bay using a continuous model type – CTB of three fields. The coupled shear wall is modeled as a continuous structure consisting of the parallel coupling of a Timoshenko extensible beam and a shear beam. Using a variational approach, the equilibrium equations, constitutive laws, and boundary conditions are derived by applying Hamilton’s principle to the relevant Lagrangian function. Closed-form solutions are provided for the static deflection of the coupled shear wall under general profile lateral loads and the periods of vibration of the coupled shear wall under vertical loads uniformly distributed along its height. A validation of the static analysis was carried out, and to find the range of validity of the continuous model and proposed solution methods, a parametric analysis was carried out. The results are encouraging and show that the proposed analytical solutions have excellent correspondence with respect to the finite element method; they are accurate, reliable and involve low computational cost at a preliminary stage, and can be used as a verification method at the final stage of structural analysis and design.

Seismic performance of hybrid coupled shear walls

AbstractHybrid Coupled Shear Walls are an innovative seismic‐resistant system that aims at merging the advantages of the classical Coupled Shear Walls with the dissipative capacity and easy‐to‐repair characteristics of steel elements. They are constituted by a reinforced concrete wall connected to two side steel columns by dissipative steel links. Depending on the stiffness/strength of the links, it is possible to obtain different distributions of the seismic forces between the wall and the columns. As resulting from previous research activity on this topic, the seismic behavior of this structural system can be strongly influenced by the higher modes, especially for mid/high‐rise buildings, making classical pushover analyses unable to catch the correct behavior. In this regard, the paper presents the comparison between the results of Incremental Dynamic Analyses and of different Pushover Analyses, giving indications about a more reliable procedure for the assessment of the seismic performance through suitable pushover analysis.

Experimental behaviour of optimized hybrid coupled shear walls

AbstractThis paper shows the experimental structural behaviour of an optimized solution for hybrid coupled shear walls, which are seismic‐resistant systems composed of a reinforced concrete wall, with two side steel columns connected by beams ‐ the dissipative element. The optimized solution is proposed to upgrade the global behaviour of the system, with the aim of reducing the bending moment at the base of the reinforced concrete wall. Indeed, previous experimental tests demonstrated that the wall may suffer from early cracking at the base, despite the possibility of controlling the base bending moment thanks to properly balancing stiffness and resistance of the different components of the system. The optimized solution is numerically developed and designed with the philosophy of redistributing bending at the base of the wall by removing the lateral portions of the concrete and replacing them with a couple of steel hinged profiles, to control the deformations and absorb the torque. The central concrete part of the wall is kept but reduced to the minimum, to transfer the shear, only, reaching closely hinged‐like conditions. Two different solutions are proposed for the central reduced part of the wall: in the first case, the cross section is gradually reduced to the base, while in the second one, the wall is connected through a steel pin to the base. Both solutions are tested under monotonic load for a preliminary assessment of the actual benefits at the base of the wall compared to the original proposal.

Cyclic response and parametric study of a self-centering coupled shear wall system with disc spring devices

The use of the disc spring device (DSD) to provide a superior self-centering ability and ductility for shear walls has been investigated in both numerical simulation and pseudo-static cyclic loading tests. In the current study, the DSD is adopted to improve the resilience of the coupled shear walls. A finite element model of a present coupled shear wall is developed and verified by the experiment. Based on the prototype model, a model of the self-centering coupled shear wall system is built by installing two DSDs in the bottom corners of the wall piers. A parametric study is performed to provide a holistic evaluation on the effect of the stiffness, friction, and installation layout of the DSD. Results prove the resilience promotion of the traditional coupled shear wall by installing DSDs. The sufficient initial stiffness of DSDs can provide high overturning moment capacity and the second stiffness of DSDs is key in mitigating the residual displacement for the self-centering coupled shear wall. The friction between disc springs can enhance energy dissipation ability of the system. More installed DSDs would be beneficial for the ductility of the coupled shear walls.

Economic Earthquake Resistance Construction of High-Rise Buildings

The economic perception of earthquake resistance construction for medium- to high-rise RCC buildings is examined in this paper. The conventional way of creating high-rise buildings is not financially viable without a shear wall to withstand seismic energy. Framed structures with irregular floor plans that vary in size, shape, and geometry are also expensive. Many studies have been conducted recently on the Coupling Ratio (CR). The current analysis investigates the behavior of the coupled shear wall and the CR for an affordable earthquake resistance construction including the shear wall within a range of 30 % to 45 %. The study shows that shear walls could be reduced at 40–50 % and at 60–70 % of the base height for regular and irregular buildings, respectively. The current study also comes to the conclusion that coupled shear wall earthquake-resistant construction is more practical than the conventional approach because couple beams can be repaired with ease.

Experimental study on seismic performance of modular cast-in-situ coupled shear wall with LRC infill wall

Experimental study on seismic performance of modular cast-in-situ coupled shear wall with LRC infill wall

Resilience of Medium-to-High-Rise Ductile Coupled Shear Walls Located in Canadian Seismic Zones and Strengthened with Externally Bonded Fiber-Reinforced Polymer Composite: Nonlinear Time History Assessment

Coupled shear walls (CSWs) are structural elements used in reinforced concrete (RC) buildings to provide lateral stability and resistance against seismic and wind forces. When subjected to high levels of seismic loading, CSWs exhibit nonlinear deformation through cracking and crushing in concrete and yielding in reinforcements, thereby dissipating a significant amount of energy, leading to their permanent deformation. Externally bonded fiber-reinforced polymer (EB-FRP) sheets have proven to be effective in strengthening RC structures against various loading and environmental conditions. In addition, their high strength-to-weight ratio makes them an attractive solution as they can be easily applied without significantly increasing the structure’s weight. This study investigates the effectiveness of using EB-FRP sheets to reduce residual displacement in CSWs during severe earthquake loadings. Two series of 15-story and 20-story CSWs in Western and Eastern Canadian seismic zones, which serve as representative models for medium- and high-rise structures, were evaluated through nonlinear time history analysis. The numerical simulation of all CSWs and strengthened elements was carried out using the RUAUMOKO 2D software. The findings of this study provided evidence of the effectiveness of EB-FRP sheets in reducing residual deformation in CSWs. Additionally, significant reductions in the rotation of the coupling beams (CBs) and the inter-story drift ratio were observed. The results also revealed that bonding vertical FRP sheets to boundary elements and confining enhancement by wrapping CBs and wall piers is a very effective configuration in mitigating residual deformations.

Nonlinear Behavior of the Concrete Core of the Diagonally Reinforced Coupling Beams

Coupled shear walls with coupling beams are constructed because of openings such as doors, windows, or other installations that are left behind due to functional reasons in shear walls. In coupling beams having a ratio of span-to-depth less than two, shear fracture occurs rather than flexural fracture. In order to meet the shear force and the bending moment formed by the coupling beams, diagonal bundles are used in the coupling beams. Diagonal reinforced coupling beams are generally preferred because diagonal reinforced coupling beams exhibit better behaviour than conventional reinforced coupling beams. The diagonal reinforcement bundles have to be confined by transverse reinforcements prescribed in the codes. Confined concrete in the diagonal reinforcement bundles has stress-strain characteristics that are distinctly different from those of plain concrete. The effects of longitudinal and transverse reinforcement ratios on the stress-strain behaviour of confined concrete inside the diagonal reinforcement bundles were investigated. Fifty-four reinforced concrete coupling beams with different confining parameters of the diagonal reinforcement bundles and different variables were analysed using the program. It was demonstrated that the strength and the maximum strain of the concrete inside the diagonal reinforcement bundles increase with the reinforcement ratio of the confinement reinforcement. The increase in the diameter of the transverse reinforcement and the decrease in the spacing of the transverse reinforcement diagonal bundles, increase the confining effect, strength, and ductility in the concrete sections. The increase in the ratio of transverse and diagonal reinforcement significantly affects the seismic behaviour of the coupling beams.

Seismic behaviour of assembled monolithic concrete coupling beams through tests of two-story coupled shear walls

In the prefabricated concrete shear wall structure, in order to further improve the construction efficiency, the underwindow wall and the wall pier on both sides are often prefabricated as a whole. Therefore, the assemble integral coupling beam is composed of a prefabricated under-window wall, a cast-in-place strip and a prefabricated upper-window wall. The failure mode of this type assemble integral coupling beam under cyclic loading has not been reported. Because the wall under the window is also merged into the coupling beam, the length-to-depth ratio of the coupling beam is further reduced. However, the upper and lower walls are prefabricated standard walls with opening, which cannot be configured with inclined bars, which is a common way for cast-in-place coupling beams with relatively small length-depth ratio. In addition, how to connect the upper and lower prefabricated walls is also a key problem that affects the seismic performance. Six, two-story, full-scale assembled monolithic coupled concrete shear walls were tested to investigate the seismic behaviour of the new assemble integral coupling beam and the role of coupling beam aspect ratio (1.5, 1.85, 2.4) and connecting method (with and without grouted sleeves) between prefabricated panels on seismic performance. Two specimens were tested for each beam aspect ratio, one with a single row of grouted sleeves in the under-window panel used to splice reinforcement between the two precast panels and the other without sleeves. Test results indicate that damage in specimens with beam aspect ratios of 1.5 and 1.85 resulted from flexural yielding of beam reinforcement followed by diagonal cracking of the coupling beams, whereas damage in the specimen with larger aspect ratio (2.4) was primarily due to flexural hinging at the ends of the coupling beams. The connection details greatly affect the type and degree of damage, and more concentrated damage was observed in specimens without grouted sleeves along the interface between the precast under-window panel and cast-in-place strip. However, whether the grouted sleeve connection was used had little effect on the load capacity, deformation and stiffness of the specimens. Drift ratios at 15% drop in the peak strength ranged from 1.1% to 1.6%. The flexural capacity of the assembled integral coupling beam can be calculated as one beam according to the formula of the conventionally CIP concrete coupling beam.

Experimental investigation of the hysteretic behaviour of single-story single- and coupled-panel CLT shear walls with nailed connections

The impact of wall-to-floor hold-downs, vertical spline joints, shear connectors, panel aspect ratio, and gravity loading on the performance of single storey cross-laminated timber (CLT) shear walls was experimentally investigated. The shear walls consisted of 191 mm thick 7-ply CLT panels with nail connected hold-downs, shear brackets, and plywood surface splines. First, the strength and stiffness of the hold-downs, vertical spline joints, and shear brackets were determined. Then, a total of 27 single and coupled shear walls with panel aspect ratios of 2.5 and 3.5, gravity loading of 20 kN/m and 30 kN/m, different hold-down strength as well as different nail spacing in the splines were tested under monotonic and reversed cyclic loading. The connector tests showed that the presence of washers, even with reduced nailing, significantly increased overall connection stiffness, capacity, and ductility. The shear wall tests demonstrated that the wall aspect ratio had the most significant influence on the shear wall performance. Increasing the number of shear brackets also resulted in higher capacity, deformation, and energy dissipation, while tighter nail spacing in the spline joints resulted significant higher capacity and stiffness in coupled shear walls.

Evaluation of Static Nonlinear Behavior of Coupled Reinforced Concrete Shear Walls with Steel Beams

The shear walls are divided into two types of reinforced concrete and steel, which behave differently. In the present study, the linear and nonlinear static behavior of coupled reinforced concrete shear walls is investigated. Therefore, to validate the results, Yuan Cheng and coworkers’ laboratory model is investigated. The results of this study show that the stresses caused by external loading in the coupled shear walls are lower compared to the separate shear walls. In addition, the behavior of this system depends on the rigidity of the coupling beams. The excessive rigidity of the coupling beams does not significantly affect the behavior of these structures. Therefore, by using the continuous analytical method and ABAQUS software, a formula is proposed to calculate the dimensions of the ideal coupling beams cross-section. Based on the reviews, the proposed formula accurately predicts the nonlinear performance of the systems under investigation.

Experimental evaluation of post-tensioned hybrid coupled shear wall system with TADAS steel dampers at the beam-wall interface

Considering the optimal seismic resistance of coupled shear walls and the perks of self-centering systems, throughout this research, the hysteretic performance of post-tensioned concrete “Coupled Wall” (CW) subassemblies with “Steel Coupling Beam” (SCB) equipped with “Triangular Added Damping and Stiffness” (TADAS) steel dampers was experimentally evaluated. To dissipate the energy input from the earthquake, metallic yield dampers of the TADAS type were used at the connection zone between the beam and the wall in this structural system. Using a SCB rather than a concrete beam was suggested to reduce beam damage and maintain the system’s self-centering capabilities during lateral loading. High-strength steel strands were employed to generate post-tensioning along the beam’s longitudinal axis in the “Coupled Wall System” (CWS) to reduce structure residual deformation under seismic loading. In the first portion of this research, an experimental assessment of the load–displacement behavior of TADAS dampers exposed to cyclic loads was performed. Then, at floor level, three ⅔-scaled CW subassemblies were constructed using a post-tensioned SCB and subjected to lateral quasi-static cyclic loading of increasing amplitude. Various post-tensioning stresses were applied to one subassembly lacking energy dissipation devices and two subassemblies with TADAS dampers. The findings demonstrate that TADAS-equipped subassemblies can endure major non-linear deformations up to 8% drift without struggling either residual deformation or severe injury. Installing TADAS dampers at the beam-wall interface heightened the specimens’ capacity to withstand lateral loads by 71% to 90% and considerably increased their potential to dissipate energy.

The effect of precast concrete infill wall on the seismic performance of PCCSW

Lateral stiffness provided by infill walls to the building structures is generally neglected in designs. However, the infill walls, served as the main nonstructural component, have significant influence on the seismic behavior of the main structures during seismic events. To investigate the effects of the infill walls on the seismic behavior of the precast concrete (PC) coupled shear walls (PCCSW) with infill walls, lateral cyclic loading tests were conducted on three PC coupled shear walls, including two specimens with rigid and flexible connections between the PC coupled shear walls and infill walls, and a specimen without infill walls for comparison. The test results showed that the infill walls can improve the strength and stiffness of the PC coupled shear walls but at the cost of the ductility and energy dissipation, especially for the specimen PCCSW with rigid connection. In addition, the finite element analysis (FEA) models of the PC coupled shear walls were proposed, and the reliability and accuracy of the FEA models were validated based on the test results. Subsequently, a parameter study was conducted to assess the influence of the critical parameters on the mechanical behaviour of the shear wall. Finally, the simplified calculation methods for the peak strength of the shear wall were also proposed, and the theoretical results matched well with the test and simulation results.

A unified section-based restoring force model for reinforced concrete coupling beams based on the XGBoost model: Establishment, validation and application

To enhance the seismic performance of reinforced concrete (RC) coupling beams, improved reinforcement details such as diagonal layout and high-performance concrete including fiber reinforced concrete (FRC) as well as engineered cementitious composites (ECC) are widely investigated and applied. Despite the numerous experimental studies on various reinforced concrete coupling beams, there is still a lack of unified, efficient and accurate numerical model applicable to all kinds of concrete and reinforcement layouts, leading to difficulty in numerical study and proper design of coupling beams and coupled shear walls. In this study, a database containing 180 reinforced concrete coupling beam specimens is first set up. Then the key mechanical indexes of test curves including the peak load, peak beam rotation, yielding beam rotation and softening beam rotation are predicted using the trained XGBoost models. The feature importance and partial dependence of different independent variables are analyzed. Based on the predicted results, the skeleton curves of the section-based restoring force model can be obtained. Besides, a new hysteretic rule for the restoring force model which can account for the pinching effect, strength and stiffness degradation is proposed. The proposed model is then implemented in ABAQUS 2017 software, of which the accuracy and applicability are validated by twelve coupling beam specimens with different concrete materials and reinforcement layouts. Finally, a coupled shear wall specimen is simulated to quantitatively and thoroughly evaluate the effects of key indexes of the coupling beams on the seismic performance of the coupled shear wall structures.

Seismic behavior of precast concrete coupled shear walls with yielding-based and friction-based coupling beams

Seismic behavior of precast concrete coupled shear walls with yielding-based and friction-based coupling beams

An Efficient Model for the Coupling Beam Using Damping Devices in Coupled Shear Wall Structures under Earthquake Loads

This paper proposes a new element for modeling the energy-dissipation coupling beam to analyze the coupled shear wall structure under seismic loading. The new beam element includes 2 rigid beams and an energy dissipation device in the middle. The element stiffness matrix is derived based on principles of nonlinear mechanics. A procedure of the incremental-iterative solution is built using the Newmark method and adopted for solving the nonlinear equation of motion. A computer program using Matlab is developed to analyze the behavior of frame analogy which is modeled from the couped shear wall structure. Several numerical examples are presented to verify the developed program with the commercial finite element package SAP2000. The numerical results proved that the proposed program is efficient and reliable. The proposed element and program are then applied to analyze a 30-story coupled shear wall structure with energy dissipation devices. As a result, the locations of the device that provide effective seismic resistance for a 30-story coupled shear wall structure are in the region from the 5th to the 15th floor or assigned on all floors.

Strengthening of deep RC coupling beams with FRP composites: A numerical study

Currently, most buildings have earthquake-resistant systems such as coupled shear walls and couple beams, designed based on previous code specifications. Also, due to specifications of new codes, diagonal reinforcement details in coupled beams are introduced, which due to the high reinforcement congestion, creates problems in fabrication and pouring. The main goal of this paper is to numerically study retrofitting with polymer composites reinforced with carbon fiber with external bonding for reinforced concrete coupling beams. The previous studies are divided into three categories. The first part concerns using externally bonded composite FRPs and the effect of fiber arrangement and thickness on the coupled beam behavior. The maximum displacement ductility in shear reinforcement patterns belonged to I and 2I patterns, which had the maximum ductility coefficients of 7.04 and 8.87. By comparing 7 CFRP reinforcement patterns, results showed that due to the mixed failure mode (flexural-shear) of the coupling beam, the U-X reinforcement pattern increased the load-bearing capacity by 18% compared with the base sample. By using suitable anchorage and preventing premature debonding, this method could be introduced as an effective method for improving the coupling beam’s behavior. In the second category, reinforcement with composite FRPs was compared with diagonal reinforcement and strengthening by installing steel plates and the accompanying behavior diagrams were given. Compared with other reinforcement methods in terms of load-bearing capacity and ductility, the specimen reinforced with CFRP and steel plates had a 49% and 70.4% increased load-bearing capacity of the control specimen. Among the studied specimens, the best performance belonged to the specimen with diagonal reinforcements, which had an increased load-bearing capacity and ductility of 124% and 4.2% compared with the base specimen. Finally, the third part is about the effective parameters of the coupling beam such as span length to height ratio and longitudinal reinforcement value regarding coupling beam behavior.

Seismic design and engineering practice of 10‐story shear wall structure with replaceable viscoelastic coupling beams

SummaryStructures with replaceable energy‐dissipating elements are attractive systems for improving building resilience. Damage in these structures is mainly limited to dissipating elements, which can be replaced after earthquakes. Among the energy‐dissipating elements, viscoelastic dampers (VEDs) can dissipate energy even under small deformations while providing stable fatigue performances, which benefits high‐rise buildings in resisting both wind and earthquake loadings. This paper presents the seismic design of an engineering practice of a 10‐story shear wall building with replaceable viscoelastic coupling beams. A new type of viscoelastic material that has negligible frequency dependency is adopted to provide stable constraint for the wall piers. The design details, including VEDs, nonreplaceable segment, and the detachable connection, are exemplified. The numerical model of the replaceable structure is established and analyzed under dynamic loadings. Results confirm that the implementation of replaceable viscoelastic coupling beams improves structural seismic performance. The plastic rotation at the end of the coupling beam is significantly reduced up to 41.4% compared with the traditional coupled shear wall structure.

Hysteretic model for bending-type frictional steel truss coupling beams

As a novel coupling beam for coupled shear wall structures, the bending-type frictional steel truss coupling beam (BFTCB) concentrates the deformation and energy dissipation in friction dampers at the bottom chord, allowing the main body to remain elastic during earthquakes. As the preparatory work for resilient structure design based on the BFTCB, this work concentrates on developing the hysteretic model for BFTCB. Firstly, the BFTCB stiffness-strength decoupling mechanism was introduced, i.e., the shear strength is provided by friction dampers while webs control its initial stiffness. Secondly, a hysteretic model that reflects the BFTCB two-stage sliding characteristic was proposed. The model consists of a trilinear backbone curve and the unloading and reverse loading rules. The model has eight control parameters, of which two core parameters (initial stiffness and limiting shear strength) are derived from the BFTCB stiffness-strength decoupling mechanism, whereas the remaining parameters are obtained by theoretical analysis and empirical calibration. The hysteretic model was then compared with the test curves and demonstrated good accuracy. Finally, a series of FE prototypes of BFTCB with different design stiffnesses and strengths was adopted to verify the hysteretic model. The results showed that the proposed model fitted well with the FE prototypes, indicating its applicability to BFTCB with varying core design parameters. Therefore, the hysteretic model can be adopted for BFTCB to support the resilient shear wall structure design.

DEVELOPMENT OF DAMPED BRACED TUBE SYSTEM AND APPLICATION TO ACTUAL PROJECT

A new vibration control system, Damped braced tube system, is developed for adopting on super high-rise buildings in central Tokyo. This system consists of tube frame using elastic braces and damped slit where a portion of braces are replaced by dampers. Damped slit acting as link beam of coupled shear wall system can dissipate seismic energy very efficiently and contribute to succeeding to meet higher seismic criteria. This paper describes system outline and efficiency through numerical analysis of actual high-rise project expected to be one of the tallest towers in central Tokyo.