Coupled Wall System Research Articles

A Study on Coupled Wall System with Post-tensioned Steel Truss Coupling Beams: Concept and Performance Evaluation

In order to improve the seismic behavior of coupled shear wall structures, a new type of post-tensioned steel truss coupling beam (PSTCB) is developed in this paper. The PSTCB is composed of chord members, two diagonal buckling-restrained energy dissipaters and diagonally placed post-tensioned tendons. The energy dissipaters are expected to serve as fuses and can be quickly repaired after earthquake. Furthermore, the residual drift of the coupling beam can be reduced by the application of post-tensioned tendons in the diagonal direction. In the PSTCB, the post-tensioned tendons are anchored at outer ends of the wall piers. According to the Chinese code, an 11-story coupled wall structure was designed and the numerical model was developed in PERFORM-3D software. The seismic behaviors of the hybrid coupled wall system with PSTCBs (HCW-P), the hybrid coupled wall system with replaceable steel truss coupling beams and concrete coupled wall system with reinforced concrete coupling beams were evaluated and compared under maximum considered earthquake. Results showed that the HCW-P can achieve excellent lateral strength, stiffness, and ductility as well as reduce the residual displacements of the structure after earthquake.

Effect of transverse reinforcement on the seismic behavior of diagonally reinforced concrete coupling beams

Coupled shear wall systems have been more popularly used in high-rise building construction in urban areas due to their efficiency in sustaining lateral loads as well as economic effectiveness. During earthquakes, coupling beams in the coupled wall system act as a seismic fuse element that dissipate most of seismic input energy exerted in the system. Diagonally reinforced concrete coupling beams (DRCBs) have been developed for this purpose. The objective of this study was to acquire test data of DRCBs of with different amount of transverse reinforcement and to evaluate the seismic behavior of these DRCBs. Quasi-static cyclic tests were conducted using seven DRCB specimens with different amounts of transverse reinforcement and different aspect ratios. Four specimens had Ln/h of 2.0, whereas it was 3.5 for the other three specimens. The shear strengths of individual specimens were compared to that calculated from the shear strength equation specified in ACI 318-14, and their deformation capacities were compared to those specified in ASCE 41-17. It is observed that the amount of transverse reinforcement in DRCBs played an important role in their shear strength and deformation capacities, indicating that the contribution of transverse reinforcement needs to be incorporated to ACI 318 shear strength equation and ASCE 41-17 model parameters.

Integrating of Nonlinear Shear Models into Fiber Element for Modeling Seismic Behavior of Reinforced Concrete Coupling Beams, Wall Piers, and Overall Coupled Wall Systems

Reinforced concrete (RC) coupled wall systems, compared with RC shear wall without opening, have more complex nonlinear behavior under the extreme earthquake loads due to the existence of coupling beams. The behavior characteristics induced by nonlinear shear deformation such as shear–flexure interaction, pinching effect, strength and stiffness deterioration are clearly observed in numerous cyclic tests of RC coupling beams and shear walls. To develop an analytical model capable of accurately and efficiently assessing the expected seismic performance of RC coupled wall systems, it is critical to define the appropriate key components models (i.e., nonlinear models of RC wall piers/shear walls and coupling beams). Classic fiber beam element based on the theory of Euler–Bernoulli beam is frequently adopted to simulate the nonlinear responses of slender RC wall piers and coupling beams in the literature because it is able to accurately model the response characters from interaction of axial–bending moment at the section level. However, classic fiber beam element cannot capture the nonlinear behaviors of non-slender structures mainly controlled by nonlinear shear deformation. To overcome this shortcoming, a modified force-based fiber element (MFBFE) including shear effect is introduced and used as the analysis element of non-slender RC coupling beams and shear walls. At the section level, a novel shear model for RC coupling beams and an existed shear model for RC shear walls are respectively added to this fiber element to simulate nonlinear responses of these two key components. The analytical model for RC coupled walls hence is formed through integrating the proposed models of these two key components. The validations with different experimental results of cyclic tests including key components and structural system reported in the literature using these proposed models are performed. Good agreements are achieved for all of these proposed models via comparisons between predicted results and experimental data.

Nonlinear seismic assessment of irregular coupled wall systems using high‐performance fiber‐reinforced cement composites

SummaryReinforced concrete coupled wall systems that consist of multiple shear walls linked by coupling beams are known to be very effective for resisting lateral loads in high‐rise buildings. As to improving the seismic capacity of coupled wall systems, high‐performance fiber‐reinforced cement composites (HPFRCCs) have been recently considered. These materials are characterized by tension strain‐hardening behavior that can improve the ductility and toughness of structures subjected to reversed cyclic loading. In this study, nonlinear finite element analyses were conducted to investigate the effects of HPFRCCs on the seismic behavior of irregular tall buildings with coupled wall systems. The coupling beams were modeled using moment hinge elements, and the structural walls were modeled using fiber elements. Comparisons between analysis and test results of coupled wall specimens with and without HPFRCCs indicate that the modeling methods used well predict both the overall and local behaviors. The responses of a 56‐story irregular tall building with coupled walls are discussed with focus on the effects of HPFRCCs. It is noted that the use of HPFRCCs in coupling beams and structural walls of one‐fourth height from the base greatly affects the failure mode. For irregular tall buildings, nonlinear response history analysis indicates higher mode effects are critical.

Coupling Ratio‐Based Design and Seismic Performance of Modular Prefabricated Hybrid Coupled Walls

Based on the advantages of modular prefabricated multistory steel structure, a full‐bolt‐connected modular steel coupling beam‐hybrid coupled wall system is presented. Further, a method of estimating the coupling ratio (CR) is proposed according to the continuous link method. A CR‐based seismic design procedure is determined such that the structure utilizes the lateral stiffness of the shear wall, which is necessary to avoid structural damage under frequently occurring earthquakes. However, it also exhibits excellent ductility of the coupling beams, which is necessary for dissipating energy under infrequent earthquakes. Subsequently, nonlinear hysteretic analyses are conducted from finite element analysis software ABAQUS, and a parametric study based on the finite element technique is performed to identify the optimal value of the coupling ratio. Results indicate that the seismic performance of modular prefabricated HCWs was excellent, and the basic requirements for ductile behavior and lateral stiffness were satisfied for CR values from 50% to 60%. The obtained results confirm the accuracy of the CR‐based seismic design method proposed in this study and are supported by the selection of the design parameter at the initial design stage.

Seismic performance and design method of PRC coupling beam-hybrid coupled shear wall system

Seismic performance and design method of PRC coupling beam-hybrid coupled shear wall system

Seismic performance evaluation of coupled wall system with novel replaceable steel truss coupling beams

Coupled wall systems are often used in high-rise buildings in zone of high seismic risk to provide lateral resistance to earthquake loading. Once damaged, reinforced concrete coupling beams are costly and time-consuming to repair post-earthquake. To enhance the seismic resilience for coupled wall structures, a novel replaceable steel truss coupling beam is first introduced. The proposed replaceable steel truss coupling beam consists of chord members at the top and bottom, respectively, and two buckling-restrained energy dissipaters are employed in the diagonal direction. The energy dissipaters can yield first before the wall piers and dissipate large amounts of energy to protect the main structure under seismic loadings. In addition, the energy dissipaters can be easily installed and post-earthquake repaired through pin connection with the chord members. This article mainly focused on the numerical and theoretical analyses of the proposed replaceable steel truss coupling beam, and nonlinear analytical models were developed in PERFORM-3D. An 11-story prototype structure was designed per Chinese code. The seismic response of hybrid coupled wall system with replaceable steel truss coupling beams was evaluated using nonlinear time history analysis and compared with the response of reinforced concrete coupled wall system with reinforced concrete coupling beams under seismic loadings. Results show that the proposed replaceable steel truss coupling beam leads to a good seismic response with reduced interstory drifts of the systems and rotational demand in the beams and wall piers due to a large energy dissipation capacity and overstrength.

Assessment of dynamic behavior and seismic performance of a high-rise rc coupled wall building

This study evaluates the seismic behavior and performance of a code-based high-rise RC coupled wall building located at the site with high seismicity representative of the West cost of the United States. Modeling approach for dynamic analysis of a coupled wall system is developed based on novel model for RC walls that captures nonlinear axial-flexure-shear (P-M-V) interaction and is validated using detailed experimental data available in the literature, providing the opportunity to analyze the behavior of this system from the new perspective. Seismic performance assessment is conducted considering structural and nonstructural building components based on two performance metrics: repair cost and repair time. The loss metrics are evaluated using FEMA P-58 methodology in conjunction with a realistic repair time model considering frequent (50% in 50 years), rare (10% in 50 years), and very rare (2% in 50 years) earthquake events. Analysis results reveal that strong ground shaking causes significant variation of axial forces in piers of the coupled wall system resulting in P-M-V interaction and considerable shear-related damage (cracking) over most of the wall height, while coupling beam rotations and corresponding damage are relatively small due to their excessive capacity obtained from the code-based design. Although median repair cost is relatively low, less than 6% of construction cost for frequent and rare earthquakes and about 24% for very rare earthquakes, building functionality is impaired at all hazard levels ranging from few weeks for frequent earthquakes to several months for very rare earthquakes, predominantly driven by damage to wall piers and slab-column connections.

Analytical model for seismic simulation of reinforced concrete coupled shear walls

Reinforced concrete coupled walls are widely used as the main seismic resistant structural system in high-rise buildings. This paper proposes a new mixed beam-shell model for the seismic analysis of reinforced concrete coupled walls with sufficient efficiency and accuracy on the platform of general finite element software MSC.Marc. Boundary elements at the ends of wall piers are simulated by conventional fiber beam-column elements, while the web of the wall pier is modeled by the layered shell element. Coupling beams are simulated by non-conventional fiber beam-column elements, which can not only take into account the shear and shear-sliding deformation together with various failure modes of conventionally reinforced beams, but also the shear and rebar slip deformation of diagonally reinforced beams. RBE2 link elements are utilized to connect the coupling beams to the wall piers. Eight test specimens reported in the literature are used to validate the proposed model. The mechanism of the coupled wall is thoroughly investigated in terms of the beam deformation, base shear and moment distribution as well as axial force of the wall piers. Furthermore, parametric analyses on specimens with different degrees of coupling and types of reinforcement layouts of coupling beams are conducted. Based on the analyses, the influences of the complex behavior and various modeling parameters of coupling beams on the behavior of coupled wall are revealed quantitatively. As a conclusion of the parametric analyses results, it is recommended that the complicated behavior of coupling beams be accurately considered for most cases in the seismic analysis of coupled wall systems.

Shear migration and dynamic shear amplification effects on seismic response of core walls

Dynamic shear amplification and shear migration are two important phenomena that could be critical for shear design of structural core walls. Dynamic shear amplification has been studied for cantilever walls since 1970s. Similarly, shear migration phenomenon has been observed at coupled wall tests since mid-1970s. Yet, there is no consensus among seismic design codes for consideration of the effects of dynamic shear amplification and shear migration, especially for coupled wall systems. The paper presents the effect of dynamic shear amplification on cantilever walls and shear migration effect on coupled core walls, which are vital elements for seismic design of tall buildings. Demonstrative examples on core walls are presented for both phenomena.

Nonlinear Seismic Response Analysis of an Innovative Steel-and-Concrete Hybrid Coupled Wall System

This paper studies the seismic response of an innovative hybrid coupled shear wall (HCW) system, obtained through the connection of a reinforced concrete (RC) wall to two steel side columns by means of steel links. This structural solution is conceived to exploit both the stiffness of the RC wall, required to limit building damage under low-intensity earthquakes, and the ductility of the steel links, necessary to dissipate energy under medium-intensity and high-intensity earthquakes. The seismic performance of the proposed HCW system is evaluated through multirecord nonlinear dynamic analysis of a set of case studies designed on the basis of a specific ductile design procedure. The adopted finite-element models are illustrated and validated with experimental tests and more complex three-dimensional numerical models. A selection of results is presented and discussed to highlight the potential of the proposed innovative HCW systems and the possibility to develop a ductile mechanism in which plastic deformations are mainly attained in the steel links, with minor damages in the RC wall.

Cyclic Behavior of Deep RC Coupling Beams with Different Reinforcement Layouts

ABSTRACTAn experimental investigation on the seismic behavior of deep reinforced concrete coupling beams was conducted by testing six large-scale coupling beams with different reinforcement layouts. The reinforcement layouts included using concealed beams similar to wall boundary elements, U-shaped steel, through-slits, diagonally embedded steel plates and diagonal rebar bundles without confining ties. Test results indicate that coupling beams with diagonal steel plates or diagonal rebar bundles without confining ties showed the most desirable deformation and energy-dissipation capacities under cyclic loading, and thus are viable alternatives for coupled wall systems in seismic zones.

Seismic Behavior of Bolted Endplate Connection Between Steel Reinforced Concrete (SRC) Wall and SRC Beam for Use in High-Rise Buildings

To improve the constructability of the steel and concrete composite coupled wall system while maintaining good seismic performance in terms of strength, stiffness and energy dissipation capacity, the bolted endplate connection between steel reinforced concrete (SRC) wall and SRC beam has been proposed and studied. The endplate is shop welded to the end of steel beam and then fastened to the flange of steel column at boundary element of wall pier through high-strength bolts before the fabrication of reinforcement cage and concrete pouring for the composite beams. Five SRC beam-SRC wall subassembly specimens were designed, constructed and tested subjected to cyclic displacement reversals at SRC beam end. The test parameters included the amount of steel plate embedded in SRC beams and the influence of slab. The responses of the specimens in terms of load–displacement hysteretic responses, cracking patterns, ductility, strength and stiffness degradation characteristics were discussed. The test results show that through rational design the bolted endplate connection can satisfactorily ensure the load transfer mechanism between SRC beam and SRC wall such that the SRC beam can fully develop its strength, ductility, post-yield strength and stiffness retention capacities. The strength, post-yield deformation and energy dissipation capacity of SRC coupling beams can be effectively enhanced by increasing the steel plate ratio. The existence of slab can enhance the overall seismic performance of SRC beam. Nonlinear finite element modeling approach was developed and verified by comparison with the test results, showing good agreement in terms of the skeleton and hysteresis curves.

Seismic Behavior of Hybrid Coupled Wall System

Reinforced concrete (RC) couple wall systems, where RC beams couple two or more RC walls in series, are frequently used in high-rise buildings. Generally, coupling beams are made of RC materials. Steel coupling beam is an alternative for RC coupling beam which has a complex and and unefficient detailing construction. This paper presents a study on the use of Hybrid Coupled Wall System (HCWS) in seismic resistant high-rise RC structures. In the study, 25 storey office buildings with three types of coupling beams and three types of walls distributed over the height of the structure and located in a region with high seismicity are designed. Applying a performance-based design approach, this study developed an efficient design for RC structures having Coupling Ratio (CR) values 64.55% and affect the behavior of the wall pier in the upper region of the structure where widespread plastification and earlier crushing failure happen. Based on this findings, steel coupling beams can be used as an alternative with statisfying all performance criteria and perform at Life Safety(LS).

Analytical Investigation of the Applicability of Seismic Devices for Core Frames System in High-Rise Buildings

The use of link element in high rise buildings has been applied widely and proven to be effective in the eccentric braced frame system. Latest research has also shown that the applicability of link element can be extended to other type of structural systems, such as: coupled wall system or structures with core wall. The research showed that the use of link element could lead to better deformation capacity of the system and the link elements could act as a “fuse” to limit the input of earthquake force. However, the improvement of the seismic behavior may not be effective for any type of structural system. This paper investigates analytically parameters affecting the effectiveness of the application of shear link elements within a structural system. Several parameters being studied are the relative stiffness between link element and structural stiffness, types of structural configuration, etc.

A simplified analytical model of dynamic behavior of hybrid coupled wall systems with steel coupling beams

This paper proposes a simplified analytical model to estimate the seismic response of hybrid coupled walls (HCW). The model tends to consider the inelastic behavior of steel coupling beams (SCB) and elastic behavior of wall piers. The two wall piers are simplified to one cantilever beam with equivalent stiffness. The steel coupling beams were simulated by rotational springs, and their actions on the walls were represented by concentrated moments distributed along the height. A bilinear hysteretic model is used to represent the inelastic behavior of SCBs. The Rayleigh-Ritz method is adopted to determine the seismic response of the simplified model. The performance of the simplified model is verified against finite element analysis of a 20-storey HCW building. The comparison shows that the simplification is reasonable to capture the main dynamic characteristics of HCW systems. Parametric studies are conducted and the results show that the yielding level and post-yielding stiffness of SCBs have significant influence on the dynamic behavior of HCW systems. To achieve the optimum performance, it is recommended to reduce the yielding level of SCBs by 40–60%, and to design the post-yielding stiffness ratio of SCBs in the range of 0.4–0.6.

Cyclic behaviour of slender diagonally reinforced coupling beams with various amounts of transverse reinforcement

Coupled shear wall systems are very efficient in resisting lateral forces induced by wind and earthquake loads. Recently, slender diagonally reinforced coupling (DRC) beams have been commonly used for coupled shear wall systems in high-rise building construction, which allows reduction of storey height and construction cost. The objective of the present study is to investigate the effect of transverse reinforcement on the cyclic behaviour of slender DRC beams. For this purpose, experiments were conducted using three DRC specimens with various amounts of transverse reinforcement. An equation for accurately predicting the shear strength of slender DRC beams is proposed.

Fiber beam-column model for diagonally reinforced concrete coupling beams incorporating shear and reinforcement slip effects

Due to the improved energy-dissipation and deformation capacity compared to the conventionally reinforced concrete (RC) coupling beams, diagonally RC coupling beams are recommended by the ACI 318 code especially for a span-to-depth ratio of less than two and thus acquire more and more applications in coupled wall and core tube systems for tall buildings. This paper proposes a sufficiently accurate and efficient displacement-based fiber beam-column model for the nonlinear seismic analysis of diagonally RC coupling beams with span-to-depth ratios ranging between one and five. The model is developed on the platform of a general FEA package MSC.Marc. First, the conventional fiber beam-column element is modified to consider the flexural contribution of diagonal bars. Then the new section shear force-shear distortion and slip deformation rules are proposed and incorporated into the modified fiber element, respectively, since both the shear and reinforcement slip are critical mechanisms influencing the seismic performance of the beam. The equations for critical model parameters including the cracked shear stiffness and chord rotation limit are developed and verified based on the results of sixteen test specimens collected from previous research. The model is utilized to simulate the collected specimens together with a coupled wall system and proves to be a powerful tool for the nonlinear seismic analysis of diagonally RC coupling beams and coupled walls with satisfied accuracy, efficiency and modeling convenience.

11.33: Performance evaluation of an innovative HCW system with Shear Dissipative Links

ABSTRACTThis paper presents an improved approach to a newly suggested design procedure of an innovative Hybrid Coupled Wall (HCW) system. This system consists of a reinforced concrete (RC) shear wall with dissipative steel links and steel side columns, where the RC wall carries almost all the horizontal shear force while the overturning moments are partially resisted by an axial compression‐tension couple developed by the two side steel columns rather than by the individual flexural action of the wall alone. The 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. This increases the energy dissipation ability of the whole system and thus improves its resistance towards seismic ground motion. This present piece of investigation also aims to bring clarity to some important points such as: definition of an efficient coupling ratio with or without uniform link distribution, lower and upper limits of the coupling ratio compatible with the assumed link distributions, relationship between the coupling ratio and the total building height. The proposed design procedure is applied to case studies considering various assumptions for the design parameters. The designed solutions are analysed through several nonlinear finite element models in order to evaluate the results of the design methodology and provide useful information on the ductility capacity of the proposed innovative HCW system for different coupling ratios and efficient energy dissipation characteristics of the shear links.

Effect of Steel and Concrete Coupling Beam on Seismic Behavior of RC Frame Accompanied with Coupled Shear Walls

Construction of diagonal reinforcement in concrete coupling beam is difficult so its replacement is steel coupling beam. Literature shows that a few studies have been done on seismic behavior of RC coupled wall with steel coupling beam. In this paper, the influences of increase in building height on the seismic nonlinear behavior of dual structural systems in forms of RC frames accompanied with RC coupled shear walls once with concrete then with steel coupling beam have been investigated. Therefore the buildings with 7, 14 and 21 story and containing RC coupled wall systems with concrete and steel coupling beams used to perform the pushover analysis having different load patterns. Some seismic parameters such as ductility factor, response modification factor due to ductility, over-strength facto, response modification factor (R) and displacement amplification factor (Cd) have been studied. Regarding the results, the response modification factor for the mentioned structural system is higher than the values which are used in Codes of practice for seismic resistant design of buildings. Also, the displacement amplification factor and the response modification factor increased as the structure height decreased and the value of these factors at steel coupling beam structures are higher than concrete coupling beams.