Achieving targeted levels of reliability for low-rise seismically isolated structures. Issue 125 (October 2019)

• Record Type: Journal Article
• Authors: Shao, Benshun; Mahin, Stephen A.; Zayas, Victor
• Is Part Of: Soil dynamics and earthquake engineering. Issue 125(2019)
• Publication Date: 2019-10
• Subjects: Seismic isolation -- Reliability target -- Capacity of isolator -- FEMA P695; Soil dynamics -- Periodicals; Earthquake engineering -- Periodicals; Sols -- Dynamique -- Périodiques; Génie parasismique -- Périodiques; 624.176205
• DOI: 10.1016/j.soildyn.2019.105744
• Languages: English
• ISSNs: 0267-7261

Abstract

Abstract: By interpreting the seismic responses of two seismically isolated low-rise case-study buildings probabilistically using FEMA P695 methodology, the study indicates for the design of seismically isolated structures, providing isolator capacities equal to risk-targeted maximum considered earthquake (MCER ) demand does not achieve targeted levels of reliability specified in ASCE 7–16. To do so, isolation system capacities beyond average MCER demand are required. The minimum required capacities for using three types of enhanced isolation system (isolator without displacement restraint, isolator combined with external hard-stopping mechanism, and isolator with internal stiffening behavior at large horizontal displacement) are calculated with nonlinear response history analysis following probabilistic framework for different design risk categories numerically. The results indicate that isolator displacement capacities ranging from 1.5 to 2.60 times the average MCER demand and isolation system shear capacities ranging from 1.5 to 5 times the average MCER demand are required, depending on seismic risk categories and isolation system types. The use of an isolator with internal stiffening behavior is an efficient option to provide the required capacities for achieving reliability goals, especially for high risk-category design. Highlights: Current design regulation results into high probability of failure for isolator. Significant larger isolator capacity than ASCE 7 requirement is needed in design. Large seismic gap size is needed when using moat wall for high risk-category design. Using isolator with stiffening behavior is most efficient for high risk-category design.