Study On Time-dependent Laws Of Seismic Performance Of Continuous Rigid Frame Bridge Based On Material Performance Deterioration

With the continuous improvement of infrastructure construction in China,a large number of bridges with high piers and long spans stand in the rugged terrain such as mountains and ravines in the western region.With the increase of service time,bridge structures gradually become “aging” and have a serious durability damage.Material deterioration is an important factor of structural durability damage,and it also has a non-negligible effect on the dynamic characteristics and seismic performance of the structure.In order to study the influence of material deterioration on seismic performance of continuous rigid frame bridge with high piers,it is first necessary to investigate the influence mechanism of material performance degradation on the dynamic characteristics and seismic response of rigid frame bridge with high piers,and to verify the time-dependent laws of seismic response of bridge under seismic wave excitation.Then,the time-dependent seismic vulnerability curves of bridge components and system levels are established with the dynamic incremental analysis(IDA)method based on demand capacity ratio(D/C ratio),and the influence of material deterioration on seismic vulnerability of rigid frame bridge with high piers is studied in order to provide reference for seismic safety assessment of bridges with high piers under long-term service.The main contents of this paper are as follows:(1)Based on the OpenSees,the refined finite element time-dependent models of rigid frame bridge with high piers in mountainous area are established,and obtaines the time-dependent laws of dynamic characteristics of rigid frame bridge with high piers.At the same time,the single degree of freedom systems with the same basic periods of the rigid frame bridge which change with the service age are established,and the time-dependent laws of seismic response under the action of sine waves are discussesed to reveal the influence mechanism of ground motion characteristics and material performance degradation on the seismic response of long-period bridges.(2)Artificial seismic waves are generated by design response spectrum according to detailed rules,selects actual seismic acceleration records,uses the periodic point amplitude modulation method to adjust the amplitude,and the time-dependent seismic responses of rigid frame bridge with high piers are obtained using non-linear time history analysis method to be verified by comparison with the time-dependent laws of single-degree-of-freedom systems response under sinusoidal wave excitation.It is pointed out that single-degree-of-freedom systems can be used to qualitatively judge the time-dependent seismic performance of long-period bridges in service.Then,evaluates the seismic performance of degraded rigid frame bridges with high piers based on the capacity demand ratio method.(3)The time-dependent seismic vulnerability analysis process of bridges is proposed with the method of incremental dynamic analysis based on the demand-capacity ratio.Obtaines the time-dependent seismic response of bridges by inputting 15 actual ground motions with amplitude modulation at periodic points to establish IDA curves of time-dependent seismic response of key components,and fits the IDA time-dependent curves based D/C ratio,obtaines the regression parameters,establishes the seismic response at component level of rigid frame bridge.The time-dependent laws of seismic vulnerability of bridge system are further analyzed,and it is pointed out that the damage probability of bridge in longitudinal direction is higher,and the influence of material deterioration can not be ignored.