Preliminary Study On Seismic Performance Of The Long Bridge Restrainer Piers For The Unseating Prevention

As a great destructive natural disaster, earthquake has done much serious harm to people,s lives and properties. Bridges as a kind of important facilities to support social and economy development, after the earthquake, will play a pivotal role of post-disaster rescue and reconstruction.A large number of beam bridges has been used in the construction of the highway in western china. while the unseating of bridge superstructure is one of the most serious earthquake damage of girder bridges.the western region is one of the main areas of high seismic intensity in china. According to the investigation of the wenchan earthquake, there are about more than fourteen hundred bridges in the region of high earthquake intensity,and some fifty bridges have collapsed, accounting for about four percent of the total bridges,such as BaiHua bridges, MiaoZiping bridge and GaoShu bridge. the primary failure leading to collapse is identified as girders falling, therefore,many researchers have studied the beam falling prevention measures. In view of the fact that abutment can availably limit the displacement of superstructure, some researchers have proposed a kind of special pier which has a larger stiffiness comparing to ordinary pier, and it is similar to the role of bridge abutment, what follows in the passage, it is called restrainer pier for short. Currently,studies on the restrainer pier are very little, in order to study its seismic performance preliminarily, some researches are carried out:1.Based on comprehensive reading of related literature home and abroad,the present methods of unseating prevation, the mechanisation of bridge suffered from unseating damage were reviewed and summed systemically.2.The bridge with a larger length than ordinary bridge have a higher seisimic displacement of superstructure in the region of high seismic intensity. After selecting a representative seismic wave and adjusting the PGA as needed, the adjusted seismic wave was used to analyse three kinds of longbridge with different span by under nonlinear dynamic time-history method, the primary analysis was the changing situation of relative displacement between beam and pier with the increasing of the bridge,s length.3.By using Midas Civil software. Considering a few important parameters, such as clearance of expansion joints, the number of expansion joints and height of the piers have been chosen to analyse the influence to the relative displacement response between beam and pier on longbridge under seismic action.4.Based on the analysis above, as for the restrainer pier, through the dynamic analysis, the performance of the restrainer pier for eliminating the bridge unseating of the longbridge with six couplets was investigated, and then applied the restrainer pier to different length bridge to analyze the seismic performances of entire bridge systemically.5.Contact collide was the way the restrainer pier works, the change of the restrainer pier stiffness impact on the collision force. Analyzing the earthquake response of the structure with different stiffness of restrainer pier by numerical analysis and comparing the constraining effect of the displacement in the longitudinal direction.6.Changing location of restrainer pier would have direct effect on the relative displacement beteween beam and pier, if we want to get effective result on the application of the restrainer pier, the key was to determine its rational position. In this paper, the restrainer pier arrangement principle in the plain terrain and slope terrain was analyzed.7.The size of the expansion joint determined the superstructure whether collision or not and the degree of collision, in view of that, considering restrainer pier top joints as an important parameter to analyze its seismic performance which was used in longbridge.