A new composite isolator named shape memory alloy cable-double friction pendulum bearing (SCDFPB), which combines a double friction pendulum bearing (DFPB) with superelastic shape memory alloy (SMA) cables, is proposed. Based on the SMA cables, the proposed isolation bearing named as SCDFPB had capability to adapt to multi-level earthquake intensities in horizontal directions, which was superior to the conventional DFPB. A series of research was performed to investigate hysteretic behavior of the SCDFPB, and a numerical simulation method for this isolation device was also developed. First, the configuration design and operation principle of the SCDFPB were described and explained in detail. Then, an analytical model of SCDFPBs was presented to understand their control and energy dissipation properties. Next, a SCDFPB specimen was designed and fabricated, and the quasi-static tests on the isolator specimen under different loading conditions were conducted to examine the isolator’s real cyclic response. The influence of displacement amplitude, vertical load and loading frequency on the hysteretic performance of SCDFPB specimen was investigated, and the behaviors of SCDFPB were compared with those of DFPB. Theoretical analyses were also performed to trace the vertical and horizontal components of the force provided by the SMA cables and their influence on the overall response of the entire isolation system during the cyclic loading process of the SCDFPB specimen. Finally, a numerical model of the SCDFPB implemented in the OpenSees program was established and validated by comparison to the experimental results.
A theoretical model of a friction pendulum system (FPS) is introduced to examine its application for the seismic isolation of spatial lattice shell structures. An equation of motion of the lattice shell with FPS bearings is developed. Then, seismic isolation studies are performed for both double-layer and single-layer lattice shell structures under different seismic input and design parameters of the FPS. The infl uence of frictional coeffi cients and radius of the FPS on seismic performance are discussed. Based on the study, some suggestions for seismic isolation design of lattice shells with FPS bearings are given and conclusions are made which could be helpful in the application of FPS.
The dynamic responses of spatial lattice shell structures with friction pendulum bearings (FPBs) under multidimensional seismic excitations are complex. In addition, FPBs may experience uplift and separation of the bearing components owing to excessive displacements. In this study, a novel multifunctional FPB (MFPB) with a multi-defense system was developed, and its effectiveness in reducing and controlling the seismic responses of spherical lattice shell structures was evaluated. The proposed MFPB comprises an FPB, superelastic shape-memory alloy cables, and sleeve restrainers. A mechanical model of the MFPB was established, and its isolation and control behaviors were investigated through numerical simulations. Furthermore, the main characteristics and advantages of the isolation system were analyzed. Subsequently, the MFPB system was applied to a single-layer spherical lattice shell structure with surrounding columns. A computational model of the controlled structure was developed using the OpenSees software. Finally, nonlinear time history analyzes were conducted to analyze the seismic performance of controlled and uncontrolled lattice shells. The results demonstrate that the MFPB isolation system can effectively control the structural responses of isolated spatial lattice shell structures under horizontal and vertical seismic excitations and improve their seismic resilience.
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