Investigation of the Base Isolation in Improving the Behavior of Steel Buildings subjected to Earthquakes applied with Different Angles

Seismic isolation is an earthquake resistant design method based on reducing seismic demand instead of increasing structural capacity. With regard to the multiplicity of studies conducted to investigate the seismic behaviour of isolators under the effect of earthquakes, in this study, role of the base isolator in improving the behaviour of steel structures under the influence of earthquakes with different angles was investigated along with considering the effect of structural height and plan shape. In the present study, steel structures with and without Lead Rubber Bearing (LRB) base isolator are modelled in 3D with 8 and 12 stories and square and rectangular plans. The seismic performance of these buildings has been reviewed and compared according to 4 pairs of near-fault earthquake records (8 records) with angles (0°, 30°, 60° and 90°) based on FEMA P695 instruction under the nonlinear dynamic time history analyses in SAP2000 software. The results showed that steel structures at angles of 60 and 90º had larger and more critical seismic responses. Based on results, the effect of seismic isolator on reducing the seismic responses of buildings at angles of 0 and 30º was low, while at the angles of 60 and 90º was more significant. The use of separators had a great impact on improving the performance and seismic responses of structures. The results also presented that in most records, the height of the structure was more effective than the plan shape regarding the seismic responses of the isolated structures.