Analytical Evaluation of MCE Collapse Performance of Seismically Base Isolated Buildings Located at Low-to-Moderate Seismicity Regions

The promising seismic response emerged by the concept of base isolation leads to increasing practical applications into buildings located at low-to-moderate seismicity regions. However, it is questionable that their collapse capacities can be ensured with reasonable reliability, although they would be designed according to a current seismic design code. This paper aims to investigate the collapse capacities of isolated buildings governed by the prescribed design criteria on the displacement and strength capacities of the employed isolation systems. In order to evaluate their collapse capacity under maximum considered earthquakes (MCEs), simplified numerical models are constructed for a larger number of nonlinear incremental dynamic analyses. The influential factors on the collapse probabilities of the prototype buildings are found out to specifically suggest the potential modifications of the design requirements. Although the MCE collapse probabilities of all isolated buildings are smaller than those expected for typical non-isolated buildings, these values are significantly different according to the degree of seismicity. The MCE collapse probabilities are dependent upon the governing collapse mechanism and the total system uncertainty. For the prototype buildings located at low-to-moderate seismicity regions, this study proposed the acceptable uncertainty to achieve a similar collapse performance to the corresponding buildings built at high seismicity regions.