Multiple-variable frequency pendulum isolator with high-performance materials

Abstract

The spherical surface of the friction pendulum system (FPS) inevitably introduce a constant dominant period, which may lead to resonance problem when subjected to the ground motions with long-period components. In this study, a multiple-variable frequency pendulum isolator (MVFPI) was developed to overcome this limitation. The sliding surface of the MVFPI was predefined as a continuous piecewise function to combine the seismic performance of MVFPI with different seismic intensities. The high-performance materials, polytetrafluoroethylene (PTFE) fabric and shape memory alloy (SMA) were utilized to improve its durability and control the deformation. Based on the underlying principles of operation, the force-displacement relationships of the MVFPI were derived. A series of tests of high-performance materials and MVFPI were conducted to verify the accuracy of the derived hysteresis model. Parametric studies and optimal analysis were carried out on the critical parameters of the MVFPI. The results indicate that the MVFPI has the desired hysteretic behavior as prescribed by the derived formulas. Moreover, the seismic responses of the structure isolated by MVFPI with optimal parameters could be controlled within the desired range.

Superelastic Conical Friction Pendulum Isolator for Seismic Isolation of Bridges under Near-Fault Ground Motions

“…In view of the effectiveness of incorporating the SMA with different isolators for response mitigation [14,[42][43][44][45][46][47][48][49][50][51][52], the advantages of the SMA, i.e., superelastic re-centering and energy dissipation, show the promising prospect of application in structural seismic resilience enhancement [33,43]. Particularly, several superelastic seismic isolators, e.g., superelastic flat sliding bearing [47][48][49][50][51][52] and superelastic friction pendulum [14,[53][54][55][56][57], in which the friction-based isolators are incorporated with the SMA wires/ cables, have been investigated and seismic performances have been analytically and experimentally demonstrated. e SMA utilized in the superelastic friction pendulum is to enhance the re-centering capacity [14,53].…”

Multi‐stage superelastic variable stiffness pendulum isolation system for seismic response control of bridges under near‐fault earthquakes

“…[29][30][31][32] Several studies have revealed that combining the SMA device with isolators is particularly efficient for residual displacement mitigation. [33][34][35][36][37][38][39] Particularly, considering the advantages of the SMA as damping and re-centering components, several SMA-based isolators, which combine the superelastic SMA wire/cables with the traditional friction isolators, have been examined for performance improvement of structures, for example, the SMA-based pure-friction sliding bearing, [38][39][40][41][42][43][44] SMA-friction pendulum bearing, [45][46][47][48][49] which demonstrated the feasibility using the SMA device to enhance the structural seismic resilience. Note that when the pure-friction sliding bearing integrates with SMA, the lateral stiffness and re-centering capability are all dependent on the SMA device, [38][39][40] which means that the SMA device needs to be fabricated using much more amount of SMA wires than the SMA-friction pendulum bearing.…”

An SMA cable-based negative stiffness seismic isolator: Development, experimental characterization, and numerical modeling

“…As a result of its variable sliding surface, the VFPI system can shift the natural frequency of the isolation system away from predominant frequency of long-period ground motions. Han et al (2020) investigated potential of combining a VFPI system with SMA wires to reduce fabrication complexity of VFPI systems and further control isolation displacements. In addition, Cao et al (2020) proposed a multi-level SMA/lead rubber bearing (LRB) isolation system to reduce isolator displacement without sacrificing isolation efficiency and increasing the force demand of substructure.…”