To investigate the seismic performance of coupled shear walls, which are connected by post-tensioned, unbonded, precast concrete coupling beams (PCCB), two 1/7-scale experiments with 8-story coupled shear walls under cyclic lateral loadings were conducted. Coupling of concrete shear walls is achieved by post-tensioning concrete beams to the wall piers using unbonded post-tensioning tendons (UPT) at the floor and roof levels. Experimental results show that little damage occurs in the coupling beams and the wall regions when the specimen undergoes large nonlinear displacements. The residual displacements of the specimen are small because of the restoring effect of the post-tensioning force. The seismic performance of three systems including CW-RC (coupled wall systems that use traditional RC coupling beams), CW-UP (coupled wall systems which use only post-tensioning tendons without steel reinforcement through the beam-wall joints), and CW-HUP (shear walls and PCCB that use combinations of steel reinforcement and post-tensioning tendons) are evaluated by means of nonlinear dynamic analysis. The calculation results indicate that the inter-story drift and peak lateral displacements of CW-HUP and CW-UP are greater than that of CW-RC, whereas the residual deformations are reduced because of the self-centering effect of the post-tensioning tendons.

Conventional reinforced concrete coupling beams are subject to severe damage after earthquakes, resulting in costly repairs or even the need for complete demolition. In order to improve the seismic resilience of coupled wall structure, a new self-centering coupling beam (SCCB) incorporating self-centering friction dampers (SCFDs) is proposed. The proposed coupling beam consists of an elastic beam segment and a fuse part. The fuse parts consist of four SCFDs arranged in a diamond shape and two chord members. The SCFD is the core component, which provides strength and stiffness to the coupling beam and reduces the residual deformation of the coupling beam. Since the damper and chord members are joined by dowels, they are easily removed and replaced after an earthquake. In addition, the SCCB can eliminate the beam elongation effect. The working principle and design methodology of the SCCB are described in detail. Cyclic loading experiments were carried out on the SCCB, and the results showed that the SCCB had good self-centering and energy dissipation capabilities. The influence of friction force and loading rates on the seismic performance of SCCB was investigated. Among all the tested specimens, the maximum residual rotation is 0.0095 rad and the minimum residual rotation is 0.0035 rad. Finally, the SCCB was tested for replacement to assess its replaceability. Experimental results show that the damaged components can be replaced by two workers within 30 min, and the seismic performance of SCCB after replacement is basically the same as before.

A new hybrid coupling beam incorporating buckling restrained energy dissipaters and viscous dampers was previously recommended. The beam can effectively reduce the floor acceleration and interstory drift ratio of coupled wall structure, and has great application prospects. However, the optimal design of a structure with hybrid coupling beams needs to consider multiple objectives, and these objectives often conflict with each other. At the same time, multiple parameters need to be optimized, resulting in a corresponding increase in the time-cost. This usually brings challenges to structural design. To address this issue, this study presents a hybrid intelligent optimization framework based on multi-objective particle swarm optimization (MOPSO) and machine learning techniques. The developed framework uses machine learning technology to quickly predict the seismic performance of structures with hybrid coupling beams, and obtain a design solution set through multi-objective particle swarm optimization. The proposed framework is demonstrated by considering a case study of a 12-story coupled wall structure with hybrid coupling beams, and it is shown that compared with the initial stage of optimization, the seismic performance of optimized structure is simultaneously improved at close cost. The floor acceleration and interstory drift ratio of the optimized structure are reduced by 11.5% and 38.7%, respectively. Finally, a formula is proposed to quantify the optimization result of pareto solution, so as to make an optimal structural design scheme. In practice, the proposed framework can provide guidance for realizing rapid and accurate about multi-objective optimization of the coupled wall structure with hybrid coupling beams.

To study the seismic behavior and influencing factors of prefabricated steel frame composite joints, cyclic loading tests of two groups of scaled specimens were carried out, and the refined numerical model was established and its validity was verified. The failure mode, hysteretic behavior and moment-rotation curve of composite joints and pure steel joints were compared, and the influence of composite slab on the mechanical properties of joints was summarized. At the same time, the parameters of the key components were selected as variables to study the changing law of the stress properties of the joints. The results indicate that the main failure modes of the overhanging end plate connection are end plate yield, bolt breakage and stiffener buckling, and the composite joints will also have local crushing of composite slab. The factors that significantly affect the bearing capacity and initial rotational stiffness of joints include the thickness of end plate, the setting of end plate stiffener, the extension of end plate, the strength of steel, the thickness of slab and the diameter of steel bars. In addition, the shape of end plate stiffeners has obvious influence on the stress distribution of joints. Finally, the calculation model of the overhanging end plate connection composite joint's initial rotational stiffness was proposed, and the stiffness superposition method was used to consider the bending stiffness of the end plate. At the same time, its reliability and high accuracy were verified, which was of great significance to engineering application.

A new type of self-centering friction damper using Shape Memory Alloy (SMA) bars is developed. The proposed damper is composed of a friction energy dissipation system and a self-centering system. Its self-centering capacity and low repair cost after earthquake make it have great advantages when applied to earthquake resistant structures. The mechanical properties of SMA bars at different heating temperatures and the seismic performance the proposed damper were experimentally investigated. Results indicated that the damper exhibits a flag-shaped hysteretic behavior under cyclic loadings. As the friction force increases, the stiffness, bearing capacity, and residual deformation of the damper increase. As the loading rate increases, the energy dissipation and residual displacement of the damper decrease. A theoretical model is presented and compared with the test results. Nonlinear numerical models were developed in ANSYS software and parametric analysis were conducted. Results showed that as the diameter of the SMA bar increases, the bearing capacity and energy dissipation of the damper increase, and the residual displacement decreases. As the preload of the SMA bar increases, the residual displacement of the damper decreases, but the dissipated energy changes slightly.

In order to improve the seismic resilience of coupled wall structure, coupling beam with fuse has been developed to reduce the post-earthquake damage. However, the fuses often have a build-up I-shaped section and are relatively heavy to be replaced. Moreover, the fuse and the beam segments are usually connected by bolts and it is time-consuming to replace the damaged fuse. For reducing the repair time and cost, a novel quickly replaceable coupling beam with buckling-restrained energy dissipaters is developed. The fuse of the proposed coupling beam consists of two chord members and bar-typed energy dissipaters placed at the corners of the fuse. In this way, the weight of the energy dissipater can be greatly reduced. The energy dissipaters and the chords are connected with hinge and it is convenient to take down the damaged energy dissipater. The influence of ratio of the length of coupling beam to the length of fuse on the seismic performance of the structure is also studied. The seismic performance of the coupled wall system with the proposed coupling beam is compared with the system with reinforced concrete coupling beams. Results indicated that the weight and post-earthquake repair cost of the proposed fuse can be reduced compared with the typical I-shaped fuse. With the increase of the ratio of the beam length to the fuse length, the interstory drift of the structure is reduced while the residual fuse chord rotation is increased.

In order to reduce the residual displacement and floor acceleration of coupled wall structures, a novel self-centering and viscous damping composite coupling beam is proposed. The proposed coupling beam consists of the elastic beam segments and the fuse part, which incorporates self-centering friction dampers and viscous dampers. The self-centering friction damper can provide strength and stiffness for the proposed coupling beam and reduce the residual displacement of the coupled wall structure. The viscous damper can add supplemental damping to the system, and this can control the peak lateral displacement demands and floor accelerations of the structure. Moreover, the proposed coupling beam can eliminate the beam elongation effect of the self-centering coupling beam with a rocking behavior. Design methodology and nonlinear numerical model of the proposed coupling beam are developed. The seismic behaviors of the coupled wall structure with the self-centering and viscous damping composite coupling beams (CW-SCVCCB) are assessed and compared with the structure with reinforced concrete coupling beams (CW-RCCB), the structure with steel coupling beams (CW-SCB) and the structure with self-centering coupling beams (CW-SCCB). Analysis results showed that the supplemental viscous damping can effectively reduce the peak interstory drift ratio and floor accelerations of the structure. The residual displacement of the novel coupled wall system is larger than that of the CW-SCCB, however, it is significantly reduced compared with the CW-SCB and the CW-RCCB.

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.

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.