Economic Feasibility Study of Self-Centering Concentrically Braced Frame Systems

Abstract

Self-centering concentrically braced frame (SC-CBF) systems have been developed to increase the drift capacity of conventional concentrically braced frame (CBF) systems prior to damage to reduce postearthquake damages. However, due to special details required by the SC-CBF system, the construction cost of a SC-CBF is expected to be higher than that of a conventional CBF. Although recent experimental research has shown better seismic performance of SC-CBF systems subjected to design-basis earthquakes, the benefit of this system must be demonstrated from an economic benefit point of view through investigating whether the higher construction cost of the SC-CBF system can be paid back by lower earthquake-induced losses during the building service life. In this study, the economic effectiveness of the SC-CBF system is assessed by comparing the life-cycle cost of the SC-CBF system with that of the CBF system in three building configurations (6-story, 8-story, and 1-story buildings). Specifically, nonlinear time history analysis is conducted in OpenSEES by subjecting the buildings to ground motion excitations. Probabilistic demand formulations are then developed for engineering demand parameters using the numerical results. Next, annual probability of exceeding damage states, the expected annual loss, and the expected economic benefit are calculated for prototype buildings considering both direct and indirect losses and prevailing uncertainties in all levels of loss analysis. In addition, this paper examines the impact of two different ground motion sets and two seismic hazard levels. The results show that the SC-CBF system is significantly beneficial over the conventional CBF for 6-story and 8-story buildings when subjected to a high seismic hazard, even with a relatively high construction cost amplification over the CBF. The 1-story SC-CBF system, however, shows no economic benefit over the conventional CBF system. The selection of ground motions has a significant influence on the loss values for both systems, but does not change whether the SC-CBF system is beneficial given the seismic hazard and building configuration. In addition, the SC-CBF system has significantly lower displacement-related damage, but higher acceleration-related damage compared to the CBF system.