Seismic Fragility Analysis Of Continuous Girder Bridge With Short Pier Using Friction Pendulum Bearing

The friction pendulum bearing has the advantages of strong self-resetting ability,excellent vibration isolation and energy dissipation damping mechanism,which accords with the concept of earthquake design based on toughness,and has been applied more and more in the design of bridge vibration isolation.Especially for continuous girder Bridges with short piers,the use of friction pendulum bearing can effectively reduce the shear response of piers under earthquake action,protect piers from shear damage and reduce earthquake losses.The performance and damage probability of vulnerable components of continuous girder Bridges with low pier with new vibration isolation system based on friction pendulum bearing were worthy of further study under different seismic effects.In this thesis,the seismic fragility of vulnerable members of a continuous girder bridge with short piers with friction pendulum bearing was studied on the engineering background of Zamora Bridge which suffered a 7.5 earthquake in 2021.It provides reference for the seismic design of similar Bridges.The main contents of the thesis were as follows:(1)The damage indexes of pier,friction pendulum bearing,cushion stone and limit baffle bolt were defined by referring to the literature.The limit values of the above components under different damage states were calculated by means of calculation formula and finite element model,which provides a basis for seismic fragility analysis of Bridges.(2)The sensitivity analysis method was used to study the influence of each structural uncertainty parameter on the seismic response of the bridge structure.It was found that the concrete bulk density coefficient,friction coefficient of the friction pendulum bearing,the damping ratio of the structure have a great influence on the seismic response of the bridge structure.(3)The seismic fragility analysis of bridge components was carried out under three working conditions.In the first condition,7 structural uncertainty parameters were considered.In case two,only three important structural uncertainty parameters were considered.The third condition was that the structural uncertainty parameters were not considered.The results show that the support,cushion stone and limit baffle bolts of the continuous girder bridge with low pier were more likely to be damaged than those of the pier under strong earthquake,which should be paid more attention to in the seismic design of such Bridges.It was found that the mean and standard deviation of seismic response under condition 1 and condition 2 were close to each other,and the damage exceedance probability curves of each component almost coincide.In order to get results quickly in engineering,only three important structural uncertainty parameters can be considered.