Effect of ground motion directionality on the seismic response of base isolated buildings pounding against adjacent structures

Seismic isolation is considered an effective design approach in averting structural and non-structural damage under severe seismic excitations. However, considerable relative displacements at the isolation level during a strong ground motion may lead to structural collisions with the surrounding moat wall and neighboring structures. Such pounding incidences, which may have detrimental consequences on the anticipated seismic behavior and performance of base isolated structures, are investigated in the presented research work. A computational methodology with the ability to capture impact forces is employed, in order to spatially examine potential structural impact with adjacent structures. Specifically, nonlinear time-history analyses of base isolated buildings, pounding with nearby conventionally fixed-supported buildings and/or the surrounding moat walls are carried out in order to examine the conditions that lead to pounding and quantify the effect of certain critical parameters on the corresponding peak seismic response. Specifically, the directionality of the imposed seismic excitations with respect to the primary construction axes of the simulated base isolated buildings is considered as an influencing parameter. The effect of other parameters, such as the clearance between the base isolated building and adjacent structures, the structural characteristics of the neighboring structures and the inclusion of accidental torsion for the seismically isolated structures in terms of mass eccentricities, is also investigated.