Dynamic Modal Updating And Seismic Response Analysis Of Dongping Bridge

Dongping Bridge in Foshan is a combinatorial bridge with steel box arch and continuous beam, which span is 300m. Vertical swivel method and horizontal swivel method are used in the construction. The vertical swivel method without buckles in steel box arch rib is initiated in China, and the weight of 14800t in horizontal swivel is the heaviest of steel arch bridge in the world. Based on this bridge, Dynamic model updating of the construction process and the state after builted are carried out in this thesis, which are based on the modal testing, and the updated modal is used as the reference modal, then seismic response of it is analyzed. The main works and conclusions included as follows:1) Because there are lots of system transitions in swivel construction method, the completely cyclical construction control system which includes analysis, measurement, identification, forecasting and adjustment is unable to establish, and the identificy and updating of control parameters are difficult to solve. Theory of dynamic Model Updating is introduced in this thesis. Based on the mearsurements of dynamic characteristics of Dongping Bridge under critical construction conditions, parameter identify and updating of the primary FE modal are done from the aspect of dynamic, further directions are given to construction, and get excellent result.2) Modal test based on environmental motivation of builted Dongping Bridge is done, and dynamic reference FE modal is obtained by modal updating based on theories. It offers theoretical laws for the dynamic analysis in later research.3) Based on the characteristic of steel arch bridge that the damping ratio is minute comparatively, the standard response spectrum is modified, then seismic response spectrum of the whole Dongping Bridge is analyzed, then the structure functional mode under the input of the worst-case combination seismic motion is obtained. The result indicates that the seismic response of the midian arch rib is greater than side arch ribs, because it suffer bigger load under dead load. There are rigidity mutation sector at the joint points of the arch, and responses under seismic shock input is major in these places, in order to reduce the stress concentration, structural design should be done.4) Traveling-wave effect is considered by adopt supermassive method, and dynamic time-history response analysis of Dongping Bridge is carried out. The result indicates that the response of the bridge under traveling-wave effect is strengthened obviously. The influence of traveling-wave effect to the main arch is bigger than to side arch and continuous beam cooperative system. It is nessesary to consider the traveling-wave effect in the seismic response analysis of long-span arch bridge.