Keywords: base isolation, seismic isolation, near-fault excitations, seismic gap, incidence angle.

The peak seismic response of a 3-story base isolated building (BIB) is investigated while varying important parameters, such as the incidence angle of the imposed seismic excitations, the available seismic clearance and potential mass eccentricities, under the action of bidirectional horizontal seismic excitations, taking into account potential poundings with adjacent structures or the perimetric moat wall. A set of 5 strong near-fault (NF), fault-normal (FN) and fault-parallel (FP) pairs of seismic recordings is used, while the angle of incidence may vary in an automated parametric procedure. The BIB is considered adjacent to a 2, 3, or 4-story fixed-supported building, which is located on its one side, while pounding may occur, not only at its base with the moat wall, but also at the upper floors of the adjacent buildings. The floor-slabs of the neighboring buildings are assumed to be located at the same levels, leading to potential slab-to-slap impacts. The parametric studies are performed using a customdeveloped software application, which enables the spatial simulation of base-isolated buildings modeled as 3D MDOF systems with shear-type behavior with impact capabilities. The slabs are modeled as rigid diaphragms and the masses are lumped at the floor levels with 3 DOF at each floor. The impact modeling is based on an overlapping region and a contact plane according to which normal and tangential impact forces can be assessed, while the Coulomb law of friction restricts the magnitude of the tangential impact forces. The equations of motion of the simulated whenever there is contact, and numerically integrated. The conducted parametric analyses indicate that the necessary width of the provided seismic gap depends on the characteristics of both the earthquake excitation and the structural characteristics, as well as the incidence angle of the imposed earthquake excitations. Furthermore, the extent at which the incidence angle influences the peak response depends on the structural systems and the separation distance. Since the computed results cannot be generalized, numerical simulations and parametric analyses should be performed for each particular case in order to identify the most critical seismic response and obtain a more reliable assessment of the expected peak seismic response and the required clearance to avoid structural pounding in case of a very strong seismic excitation.

download the full-text of this paper (PDF, 8 pages, 577 Kb)

go to the previous paper
go to the next paper
return to the table of contents
return to the volume description