SAFETY MARGINS OF THE CAPACITY OF SEISMIC CONTROL DAMPERS IN STEEL BRIDGES AGAINST MULTIPLE EARTHQUAKES

摘要

Destructive earthquakes in recent years show that strong aftershocks are prone to occur frequently, which accelerate the destruction of structures after the main shocks. However, it is difficult to evaluate the intensity of the seismic ground motion by the aftershock. To account for this effect, it is assumed in this study that the structures would sustain three times of severe earthquakes during the service life, and for simplicity the input ground motions are repeated by three times with the same amplitude. Performance requirements on Buckling-Restrained Braces (BRBs) and Shear Panel Dampers (SPDs) installed in steel arch bridges under repeated strong earthquakes are examined by dynamic analyses, and the sensitivity of two quantities of the SPD' s capacity (maximum shear deformation and cumulative inelastic deformation) is studied. The BRBs and SPDs are designed to vary on different dimensional and mechanical parameters to be applied in a steel arch bridge, and six kinds of design earthquake motions are used. By comparing the results of three times of earthquakes with that of one time, the performance requirements are concluded and corresponding safety margin of the capacity is discussed for practical seismic design.