Shake table tests of special concentric braced frames under short and long duration earthquakes

Abstract

Several long duration and subduction earthquakes recently took place in different locations such as Chile (2015, 2014, and 2010), Japan (2011), China (2008), and Indonesia (2004). These earthquakes motivate the need to prepare for a possible long-duration, large-magnitude earthquake in the Cascadia subduction zone along the Pacific Northwest Coast of the United States. Although earthquake duration is expected to affect the response of structures and damage accumulation, current seismic design specifications do not consider duration effects. One reason might be the lack of sufficient experimental research to better understand the effect of the duration on structural performance. In this paper, an experimental program was conducted to investigate the influence of earthquake duration on structural response of steel special concentric braced frames (SCBFs). Three identical 1/2-scale one-story one-bay SCBFs with chevron brace configuration were tested on one of the University of Nevada, Reno shake tables under unidirectional short and long duration earthquakes. The overall objective was to investigate whether the duration of earthquake have an effect on the collapse capacity of SCBFs dictated by brace rupture. Test results showed that the earthquake duration affects the structural performance of SCBFs and can cause a premature failure, i.e. lower displacement capacity, because it is directly related to the low cycle fatigue life of the braces. The experimental data provided here can be used to verify fatigue damage and degradation numerical models for capturing duration effects, and support initiatives to incorporate the duration effect in future seismic design provisions and performance-based assessment frameworks.