Dynamic Impact Effect Analysis In Bridge Utilizing The Extracted Quasi-static Response

Impact factor is an important index to evaluate the impact effect of the bridge caused by passing vehicle load.According to the definition formula of impact factorμ=Ymax dyn/Ymax sta-1,in which the static response Ymax sta(deflection or strain)of the structure is a crucial calculation parameter.In existing calculation methods,Ymax sta can be calculated by numerical quasi-static simulation method or be obtained by the peaktrough method in the specifications with the dynamic test data in bridge structure.For large-scale bridges with complex structural components,the traditional static response calculation methods have some limitations,such as tough calculation efforts,limitation of parameters and low accuracy.Benefited by the achievements in dynamic testing technology and bridge structural health monitoring system,it would be very convenient and practical to obtain the quasi-static response directly from the measured structural dynamic data.Therefore,the following research works are carried out in this study:(1)Analytical solutions of the dynamic and static components in the dynamic response of the simply supported beam are derived,and the feasibility to extracting the quasi-static response is theoretically verified.Based on the dynamic and static expression equations,the cutoff frequency range in filtering process is determined.Subsequently,the solving program which coupling the two-dimensional girder bridge and the 1/2 vehicle model is written by MATLAB.Moreover,the wavelet packet analysis,low pass filtering method,and the peak-trough method are respectively applied to acquire the quasi-static response from simulation dynamic response.The results reveal that the extracting method with wavelet packet analysis to get static components has higher accuracy and applicability than other methods.(2)A three-dimensional multi-box girder bridge in Guangzhou is modeled.And the solving program of the three-dimensional vehicle-bridge coupling separation iterative method is developed with MATLAB.The proposed wavelet packet method is applied to extract the quasi-static response from the simulation dynamic response.Then,parametrical analysis is carried out with vehicle speed,road roughness and measurement position to evaluate influence to the impact factor and the wavelet packet extraction effect.(3)Subsequently,the wavelet packet method is applied with the field measurements in the serving Tianyuan Bridge in Xiamen.A set of 30 original data segments are picked out respectively representing the strain time-history in conditions that single vehicle or traffic flow passes through the bridge.The quasi-static response is extracted and combined with the simulation calculation results.The accuracy and reliability of the wavelet packet extraction method are verified.