Analysis Of Stability And Size Optimization Of Long-span Continuous Rigid Frame Bridge

Long-span continuous rigid frame bridges with high piers is symmetrical and concise. It is a bridge that spans the gorge to affort the favorable course of highway.However, the high and thin pier brings the bridge the stability problem ,that is particularly outstanding. the stability is as significant as intensity to long-span bridges with high piers. It is obvious that section parameter optimization of the high piers can reduced the cost of the bridges. In this paper, an engineering case- Yu Po Gou bridge, it is a long span continuous rigid frame bridge with thin-wall. The nonlinear stability of the high-piers is analysed by using the current FEM software ANSYS.Compare the single thin-wall with double thin-wall pier. According to the restriction of the stability and intensity, Size optimization of the high piers'section is calculated.Firstly, the paper summarizes the investigation development on stability of bridges with high-piers and some existing process, discuss two kinds of basic theories of stability about bridge structure and the simple calculational methods; further studies the linear and nonlinear FEM compution technique and process of the nonlinear stability problem. By utilizing the current FEM software ANSYS, by two types of finite element The finite element models which include degraded solid elements (shell63,shelll43) and beam elements are established for the linear and nonlinear stability comparative analysis in the construction stage andcompleted bridge stage. Two aspects are included in nonlinear stability analysis. The first one,only geometric nonlinearity is considered and the other one, geometric nonlinearity and material nonlinearity are considered simultaneously. The results show that material nonlinearity is a factor to stability coefficient that can not be overlooked. Considered the dual non-linearitys, the stability coefficient descend consumedly. It come to the conclusion that for the Long-span continual rigid frame bridge with medium-high piers(72 meter), the coefficient of stability is lowest during cantilever construction.Based on analysing nonlinear stability of Yu Po Gou bridge's two projects- single thin-wall with double thin-wall pier with equivalent area of cross scetion. The result shows that nonlinear stability coefficient about double thin-wall pier is higher than single thin-wall pier. The effect of different locations and number of the tie-girder on the stability coefficient of high piers was analyzed. It turns out to be that setting one tie-girder on the middle of pier can assure stability safety and avoid intense stress.Size optimization of the high piers'section is calculated by using the current FEM software ANSYS, by means of differential coefficient. About 26 percent of concrete material of the pier will be saved. Finally, some problems remain to be solved are put forward.