| Hekou Bridge is an important bridge project which is a fast channel from Lanzhou to Yongjing along the Yellow River. Meanwhile Hekou bridge is a long span cable stayed bridge with composite girder, which is built in highly seismic region. So it is necessary to investigate its dynamic properties and its seismic response. Different cable forces correspond with different internal forces of the main girder and the main tower. The correctness and rationality of the test of cable force can ensure that the constructed bridge can reach the design’s demand and furthermore ensure the seismic response can reach the design’s purpose.In this paper, introduce the basic theory of seismic response analysis, and then use the methods of response spectrum analysis and time-history analysis to investigate the bridge’s seismic response and finally investigate the method of the test of cable force. The main research points are as follows:① Briefly introduce the development of cable-stayed bridge in China and abroad. Meanwhile, introduce the present research situation, the methods about anti-seismic analysis, the common seismic destruction and reason of the cable stayed bridge, and the necessity of anti-seismic analysis.② Use the software of Midas/Civil which is a general finite element software, to establish the spatial finite element model of the cable stayed bridge through adequate simplification and calculate and analysis the dynamic properties of the bridge, which don’t considerate the pile-soil-structure-interaction. The result shows that the primary frequency of the bridge is 0.15334 Hz, the structural period is 6.52 s, and also shows that the structure has a long period, which is good for earthquake resistance.③ Apply the method of response spectrum analysis to calculate the bridge’s seismic response in different working condition. The result shows that the displacement response of the main tower is the most sensitive to the longitudinal earthquake input while the one of the main girder is the most sensitive to the transverse earthquake input in single direction earthquake input. What’s more, the transverse earthquake input result in the biggest internal force. To the whole structure, the increase of the response of the structure subjected to the combinative earthquake input, is obvious, and it is necessary to strengthen the seismic capacity of the main tower’s longitudinal direction and the main girder’s transvers direction.④ It is not enough to study the seismic response of the long span cable stayed bridge only through response spectrum analysis. According to relevant criterion, select three kind of earthquake action in the process of time-history analysis, discuss and compare the structure’s dynamic response in different kind of earthquake input. The seismic response caused by the three kind of earthquake actions in the same working condition are similar, and the transverse working condition in different working condition cause the biggest response of the structure. Finally compare the result of time-history analysis with the result of response spectra analysis in the same kind of working condition. In a word, the result of response spectra analysis is more smaller than the one of time-history analysis.⑤ Summarize the common theories of the test of the cable tension, the weak point of the common formulas, and the difficulty of the test such as how to consider the sag and flexural rigidity of the cable, and give the solution of the difficulty and finally give practical method of the test of cable force. Analyze the cable tension adjustment in the cable tension test. The method is based on finite element method and can consider the sag and flexural rigidity of the cable... |
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