EFFECTS OF FLING STEP AND FORWARD DIRECTIVITY ON SEISMIC RESPONSE OF HIGH-SPEED RAILWAY CONTINUOUS GIRDER BRIDGES

摘要

It is well known that forward directivity effect and fling-step effect are the two significant characteristics of near-fault ground motions differing from far-fault ground motions.To investigate the influence of such characteristics of near-fault ground motions on the seismic response of High-speed Railway Continuous Girder bridges(HRCG),this paper has selected three sets of ground motions with different characteristics and firstly conducted the response spectra analysis under SDOF,from which it can be shown that the influence of rupturing forward directivity and fling-step on the seismic structure varies along with the different structural periods.Then the nonlinear time history analysis of a 3-span HRCG bridge is proceed.The analysis revealed that under the ground motions with forward directivity pulse and fling-step effect pulse,the dynamic responses of bridge structure are more significant when compared with those non-pulse ground motions.Moreover,the velocity pulses arising from the effect of forward directivity effect has amplified more remarkably the displacement of girder and bending moment of pier bottom of the HRCG bridges,which implies that the forward directivity pulse is more damaging to the HRCG bridges than the fling-step pulse.