The Vulnerability Analysis And Damping Control Of High Pier Rigid Frame Bridge Subjected To Near-fault Earthquake Motions

The western development strategy plays a key role in accelerating the highway and railway construction in southwest and northwest of China.Due to the special topography and geology conditions of western region,high piers and long-span continuous rigid frame bridges are widely used as the main structure form to span great rivers and deep canyons.Bridge as a hub traffic routes,a vulnerability study has important significance.Seismic fragility analysis is based on a probabilistic risk assessment methods can be quantified seismic performance of the bridge.From the vulnerability point of view,this paper studies the seismic performance and influencing factors of high pier rigid frame bridges under earthquake.The main research contents and conclusions are:(1)The finite element model of the high piers rigid frame bridges is established by SAP2000,From the PEER seismic database,select the near field and far field vibration records that meet the site requirements;Determine the damage indicators of bridge components under different damage conditions;determine the vulnerability functions of bridge components and bridge systems.(2)Based on incremental dynamic analysis method,the influence of the input direction of the near-fault vibration on seismic performance of high pier rigid frame bridge is studied,which confirms that compared to the longitudinal displacement failure,The support is prone to transverse shear damage;High-pier rigid-frame bridges are more vulnerable to damage due to transverse earthquakes.Compared with the failure of longitudinal displacement,the transverse shear damage is very likely to occur in the bearings;the high pier rigid frame bridge is more vulnerable to damage due to transverse earthquakes;the vulnerability of the bridge system is higher than the individual components.Therefore,vulnerability analysis for bridge structure the system level failure events must be taken into account.(3)Making comparative analysis of seismic fragility between near-fault ground motion and far-field ground motion.Research results show that Near-fault ground motion makes the bridge more vulnerable to earthquake damage.(4)On the premise of not changing other conditions,the study on the influence of the change of pier height on the rigid frame bridge shows that,with the increase of the pier height,the surmounting probability of the bridge's various damage states gradually increases,especially the limit damage state and total failure state,and the increase of the pier height is especially serious to the bottom of the bridge pier.(5)Selecting the position of the beam,the number of the girders,the stiffness of the beam and the pier's section as the base variable,the influence of tie beam to the structure earthquake resistance performance is studied.The results show that with the increase of the number of collar beam,vulnerability of structures or components are increased.When the setting of a single beam,in central pier to set optimal collar beam effect,The stiffness of the beam has a small impact on the seismic performance of the bridge,but for the balance of the upper and lower structures,the ratio is 0.5.(6)A kind of energy dissipation device for double-limb thin-wall piers is proposed and the damping effect is verified.The results show that the installation of energy dissipation and seismic mitigation brace in the double limb pier has obvious effect on that seismic performance of the high pier rigid structure bridge.