Analysis On The Nonlinear Behavior Of Long-Span Cable-Stayed Bridges Considering Construction Process

The cable-stayed bridge is a kind of statically indeterminate flexible structure, consist of the girder, the cable and the tower. Under the effect of static force, the cable-stayed bridge is shown a clear geometric nonlinearity. As the span increases, the geometric nonlinearity of the structure becomes clearer. So the geometric nonlinearity must be considered during the finite element simulation of cable-stayed bridge.The main mission of this thesis was to study the effect of geometric nonlinearity by using Jiujiang Yangtze River Bridge as an example during the process of construction. Firstly, the development history of cable-stayed bridges and the current situation of geometric nonlinear theory were reviewed. Secondly, the limitation of small strain theory was expounds, and then the theory of large deformation was introduced. The stress tensor, the strain tensor, various methods to establish equilibrium equations after deformation and solving method were introduced. Three kinds of nonlinear factors of cable-stayed bridges and the finite element theory were described. According to the finite element software Midas/Civil, how to consider the three nonlinear factors were presented. Using Jiujiang Yangtze River Bridge as an example, the conclusion had been obtained as followed through comparison of four different analyses:(l)The effect of geometric nonlinearity may be good for the structure.(2)Because the geometrical nonlinearity had a significant impact on the deformation and internal force during the construction of large span cable-stayed bridge, it should be fully considered.(3)The effect of nonlinearity increased gradually with the increase of the cantilever length.(4)The nonlinear effect of the cable sag was larger than other two.(5)If only considering the effect of cable sag, error of calculation may appear with the cantilever length increasing.(6) During construction monitoring, the maximum absolute deviation of assembled geometry was large while only cable sag was considered. The difference of two methods gradually increased with the increase of the span and the cantilever length especially for the length of more than300m. In order to ensure the construction quality, the fully nonlinear model should be used in the construction stage.The construction monitoring of Jiujiang Yangtze River Bridge achieved good by using the above theory.