Response of asymmetric isolated buildings under bidirectional excitations of near-fault ground motions

Fitoz, Hatice Eda
Isolator displacements, floor accelerations, roof displacements, base shear and torsional moments are basic parameters that are considered in the design of seismically isolated structures. The aim of this study is to evaluate the effects of bidirectional earthquake excitations of near fault records on the response of base isolated structures in terms of basic parameters mentioned above. These parameters computed from nonlinear response history analysis (RHA) and they are compared with the parameters computed from equivalent lateral force procedure (ELF). Effect of asymmetry in superstructure is also examined considering mass eccentricity at each floor level. Torsional amplifications in isolator displacements, floor accelerations, roof displacements and base shear are compared for different level of eccentricities. Two buildings with different story heights are used in the analyses.The building systems are modeled in structural analysis program SAP2000. The scaling of ground motion data are taken from the study of “Response of Isolated Structures Under Bi-directional Excitations of Near-fault ground Motions” (Ozdemir, 2010). Each ground motion set (fault normal and fault parallel) are applied simultaneously for different range of effective damping of lead rubber bearing (LRB) and for different isolation periods.