Effects of ductility and connection design on seismic responses of base-isolated steel moment-resisting frames

摘要

In this article, effects of ductility level and connection type on seismic responses of fixed-base and base-isolated buildings with steel moment-resisting frames are evaluated using nonlinear time history analyses. In a comparative assessment of responses, a set of twenty-four models is seismically designed, including 3-and 9 story base-isolated and conventional buildings, with ordinary (OMF), intermediate (IMF), and special (SMF) levels of ductility. Each model presents two types of connections, including WUF-W and RBS. Three-dimensional models for all buildings are created in OpenSees software, and seismic responses are assessed for two earthquake scenarios. Seismic responses of buildings, such as peak floor acceleration, peak floor shear force, peak story drift, and residual and maximum displacement of isolators are calculated and analyzed. The results indicate that the ductility levels and connection types significantly affect seismic responses of base-isolated and fixed-based buildings. The RBS connection reduces the peak drift demands compared to the WUF-W connection, and the difference increases with the increment of building?s height. The SMF superstructure decreases the peak floor acceleration and peak shear force compared to the IMF and OMF ones. Moreover, the peak floor drift ratio of the OMF superstructures is larger than the IMF and SMF in base-isolated buildings. The maximum difference is computed by about 80% between the OMF and SMF superstructures.