Study On The Seismic Isolation Performance Of Bridges Based On FPB Bearing Parameters

FPB bridge seismic mitigation and absorption design isolates the structure from the seismic energy concentration spectrum and reduces the structure earthquake response in the manner of prolonging the period and increasing the damping by utilizing FPB.There is great gap between domestic standard for FPB bearing and foreign related standard at present and many scholars have a certain misunderstanding of the recovery characteristic of FPB bearing and think FPB bearing is recoverable totally.In addition,when they design the seismic mitigation and absorption of FPB bridge,they fail to consider the seismic mitigation and absorption performance of FPB bearing when the aftershock following the principal earthquake works.Based on long span of bridge in southwest region of our country,the impact of FPB bearing parameter on the residual deformation of FPB bearing is studied systematically in virtue of Midas civil software by taking a long-span continuous beam bridge as the engineering background.Further,the seismic mitigation and absorption impact of bearing parameter on the bearing with residual deformation and without residual deformation,and the impact of the existence of bearing residual information on the seismic mitigation and absorption effect of FPB are studied.It is found that:1、Through theoretical analysis of FPB bearing without residual deformation,the hysteresis model of FPB bearing with residual deformation was deduced and contrast analysis between such theoretical model and the simulated model by using the software is made to prove the correctness of theoretical analysis.2、Through changing bearing structure parameter and analyzing the residual deformation size of FPB bridge under the effect of principal earthquake and aftershock of Elcentro,Taft and Holly wave and its change with the bearing parameter change,it is known that FPB cannot be recovered totally.A certain residual deformation will be left under the effect of earthquake and FPB bearing parameter affects it,of which the bearing friction coefficient has a greater impact and the radius of sliding surface has a smaller impact.The residual deformation of bearing after theaftershock is unrelated to residual deformation of bearing after the principal earthquake and the residual deformation of bearing has no accumulation effect.3、Based on studying the residual deformation of bearing,the seismic mitigation and absorption performance impact of bearing parameter on bearing without residual deformation(under the effect of principal earthquake)and with residual deformation(under the effect of aftershock)is studied further.The research result indicates that if the value of bearing friction coefficient is bigger or smaller,it is no good for seismic mitigation and absorption performance,so the suggested selection range of friction coefficient is 0.04~0.06;the radius of sliding surface has smaller impact on these two situations,so the suggested value of FPB bearing sliding surface radius should meet Tg=2.5T0.4、Through analyzing the earthquake acting force when setting GPZ(II)bearing on the long-span beam bridge and studying the impact of the residual deformation existence of bearing on the seismic mitigation and absorption performance of FPB bearing,it is known that the residual deformation existence of FPB bearing reduces the seismic mitigation and absorption performance of FPB bearing.