Effects of Horizontal and Vertical Near-Fault Ground Motions on the Nonlinear Dynamic Response Of RC Buildings with Different Base-Isolation Systems

Abstract eng:
Near-fault ground motions are characterized by long-duration horizontal pulses and high peak values of vertical acceleration, which can become critical for a base-isolated structure. The objective of this work is to study effectiveness and limitations of base-isolation systems obtained considering High-Damping-Laminated-Rubber Bearings (HDLRBs) acting alone or either in parallel or in series with steel-PTFE sliding bearings. A numerical investigation is carried out with reference to base-isolated five-storey reinforced concrete buildings designed according to the European seismic code (Eurocode 8). The design of the base-isolated test structures (in case of HDLRBs only) is carried out in a high-risk seismic region considering the horizontal seismic loads acting in combination with the vertical ones and assuming different values of the ratio between horizontal stiffness and vertical stiffness of the HDLRBs. The behaviour of the frame members is simulated by a bilinear law, checking plastic conditions at potential critical sections. A viscoelastic model with variable stiffness properties in the horizontal and vertical directions, depending on the axial force and lateral deformation, simulates the response of a HDLRB. A rigid-plastic (with friction variability) law is assumed to simulate the behaviour of a steel-PTFE sliding bearing. The nonlinear dynamic behaviour of the test structures is studied under near-fault earthquakes.

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