On optimal triple friction pendulum base-isolation design for steel moment-frame buildings employing value-based seismic design methodology

Abstract

This paper uses the value-based seismic design methodology to optimize the mechanical and geometrical properties of triple friction pendulum bearings (TFPBs). An optimization procedure is proposed within this methodology. Initial construction cost and lifetime seismic losses are picked as the value components. Extreme failure conditions of the TFPB, less considered in the current literature, such as the uplift and exit failure modes of the curved surface sliders at the end edges, have been carefully considered in the seismic behavior of the structure. Besides, the minimum code provisions and practical limitations (e.g., the critical overturning diameter of sliders) for friction pendulum isolated buildings are regarded as design constraints. Moreover, a new cost function for TFPBs is developed from real projects of isolated buildings. The FEMA P-58 procedure is exploited to evaluate the lifetime seismic repercussions, comprising the reparation cost, reparation time, injuries, and fatalities. The endurance time method is incorporated in the FEMA P-58 procedure to estimate the structural seismic responses. A set of three buildings are chosen for evaluation, representing low-to mid-rise isolated moment-resisting frames (MRFs) with TFPBs. Each building is optimally designed with two approaches: the value-based design (VBD) via maximizing the total building value and the code-based design (CBD) via minimizing the construction cost. It is found that the total value of each isolated MRF building optimized using the CBD approach is moderately acceptable. Nevertheless, it can be notably increased using the VBD approach since it sufficiently diminishes the probability of the uplift and exit failure modes at the end edges of TFPBs.