Linear Control Analysis Of Long Span Steel Truss Cable-Stayed Bridge In Construction Stage

As the rapid development of the construction of high-speed railway(HSR) in our country, the need of long-span bridge in the construction of HSR grows with each passing day. Modern cable-stayed bridges which has beautiful shape, large spanning ability, less construction interference, good mechanical properties and perfect economic indicator, are widely used in highway bridges. But in railway especially HSR bridges, there are strict limits on control of the line shape in order to meet the demand of the vehicle smoothness. So we need to take necessary measures to control the line shape in construction stage in order to guarantee the smoothness of vehicle in operating stage.This thesis focus on the line shape prediction and controlling analysis on long-span steel-truss cable-stayed bridge in construction stage. It takes a HSR long span steel truss cable-stayed bridge’s construction stage as background, obtains its monitoring data; Firstly, ANSYS is used to build a finite model to simulate real situation, modify the model’s parameters by using the method of sensitivity analysis and parameter identification in order to get correct line shape data which are similar to real ones. Secondly, the obtained monitoring data are used to create line shape prediction model in construction stage by using theory of grey system modeling, then we use the model to predict assembling elevation in construction stage. At last, by comparing with the theoretical elevation values, line shape adjusting values can be confirmed and used in bridge’s construction by some methods. With calculation and analysis,some conclusions are obtained as follows:(1) By parameter identification in finite model, equivalent modulus of elasticity which is corresponding to real one is obtained, the result of line shape calculated by modified model is similar to real data. The biggest error in main span’s construction stages is24mm.(2) In parameter sensibility analysis of main girder’s line shape, the designed parameters’influence of line shape can be lined from big to small as cable tension, main girder’s modulus of elasticity, temporary load on some construction stages, self-weight of pressured bridge deck and self-weight of main tower. And the influence of cable tension and main girder’s modulus elasticity exists in every construction stages, but the influence of temporary load disappear as main span close. (3) Line shape prediction by using grey model has a high precision in construction stages of the cantilever erection of main steel truss girder, whose error in elevation prediction can be controlled in2cm. But in some stages, model has large defect and the error of prediction are large and uncontrollable.(4) The precision of the result of grey model is decreased by increasing of the numbers of tensioned cable, so for the last severe stages of main girder’s construction, this method should be used cautiously.