Nonlinear Numerical Simulation Study and Regional-Scale Seismic Resilience Assessment of Self-Centering Systems with Sliding Rocking Link Beams

Abstract

New trends in seismic design have resulted in proposals for several innovative seismic protection strategies, among which the concept of damage-free self-centering systems has received considerable attention. The concept involves the use of a re-centering element to bring the structure to its initial position and fuse devices for energy dissipation while the primary structural system is designed to be damage free under design basis earthquake. One challenge in implementing certain types of self-centering structural systems is the “gap-opening expansion” phenomenon which is the expansion of the frame when gap-opening at beam ends happens and causes large axial compression force in the beam and may damage the floor diaphragm.In this study, the “sliding rocking link beam” mechanism has been introduced to overcome the beam-growth issue in self-centering systems. Three high-performance systems of self-centering eccentrically braced frames with sliding rocking link beams (SCEBF-SRLs), self-centering moment-resisting frames with sliding rocking beams (SCMRF-SRBs), and self-centering modular bracing panels (SCMBPs) were developed by adopting such mechanism. The energy dissipation of the developed systems is mainly provided by replaceable hysteretic damping (RHD) devices. In the SCEBF-SRL and SCMBP systems, their recentering capability is enabled by adopting post-tensioned (PT) steel-stranded cables; and in the SCMRF-SRBs its restoring force is provided by preloaded disc springs to facilitate the pre-compression process of the rocking beam. Analytical load-displacement relationships of the three systems were formulated and cross-verified with nonlinear 3D continuum finite element (FE) analysis results, and their seismic performance was studied through nonlinear static and dynamic analysis of prototype buildings subjected to far-field and near-fault ground motions. Parametric studies were conducted to investigate the effect of key design parameters on the seismic performance of the structures. Considering the applicability of the numerical simulation and computational efficiency, four types of finite element models (FEMs) with varying levels of fidelity were developed for SCMBP systems. Additionally, the soil-structure interaction (SSI) effect on mitigating the seismic demands of the SCMBP prototype building has been studied by simulating the soil stiffness with distributed nonlinear springs as a discretized continuous medium based on the Winkler foundation method. Lastly, a digital twin framework with a python-based computational procedure was developed for performing an intensity-based seismic resilience assessment of SCMBP buildings on a regional scale. This digital twin model can also be extended to any other type of infrastructure system. The seismic damage and loss assessment is performed in accordance with the component-level FEMA P-58 methodology and the resilience metrics (e.g. repair cost, repair time, and probability of irreparability) are visualized on a geographical information system software. As a case study, the regional seismic resilience of nearly 2000 school buildings equipped with SCMBP systems was investigated for a region covering the Bay area near San Francisco, California.