Probabilistic Seismic Assessment of Isolated Buildings Considering Multiple Performance Levels

Most of current building seismic assessment methods aim to evaluate collapse risk, since the damage criteria of these methods are associated with building collapse mechanism. These methods may not be suitable for the assessment of functional facilities or seismic isolated buildings, whose performance objective is usually required to maintain their functionality after an earthquake. Hence, this study proposes a practical procedure, which consists of 7 operational steps, for seismic risk assessment of buildings considering multiple performance levels (PLs). For demonstration, a 5-story old apartment building retrofitted by sliding isolators and isolation dampers was considered in this study. The seismic performances of the building before and after the implementation of the isolation system and dampers were evaluated using the proposed method. The assessment results show that the retrofit with the isolators significantly reduced the exceedance failure probability of Collapse Prevention PL by approximately 40% under the maximum considered earthquake (MCE), and by about 50% for exceedance damage probability of Immediate Occupancy PL under the service level earthquake (SLE). This demonstrates that the proposed procedure is able to evaluate the seismic risk of either isolated or non-isolated buildings considering multiple performance levels and multiple seismic intensities.