Yaodong Bridge's Static & Dynamic Nonlinear Analysis And Solution Compare

Cable-stay bridge is a kind of complex hyperstatic structure with large span and slender proportion. The girder of cable-stayed bridge has large flexibility. And it is always under a multi-action of axis force and bending moment. Now both at home and abroad,nonlinear analysis of cable-stayed bridge has not been well-developed yet. So research on the effect of nonlinearity on cable-stayed bridge has instructional effects for engineering practice.In this paper, a general evaluate of Yaodong bridge's nonlinear effect is made, which is based on a series of linear and nonlinear analysis in which the nonlinear elastic model of concrete material is considered. With MIDAS/CIVIL applied, the paper built up Yaodong Bridge's FEM model of each construction stage and got the solution of its internal force of completion status through the linear analysis of its construction stage. Based on the solution of its internal force in completion status, material nonlinear analysis is made, in which Sargin model is considered. Then the paper made a compare between the nonlinear solution and the actual measurement. It is found that the effect of material nonlinearity on the girder's displacement is about 5%. In another word, it has certain adverse effect to the stiffness of the girder. Partly the linear solution of the cable's internal force differs great from the nonlinear solution and the actual measurement. Apparently, the linear solution is anamorphic and can not be used as a monitor of the internal force of a structure which is under great load effect. Such conclusion can be drawn that the girder's material nonlinear effect should not be ignored in engineering practice.In order to observe the effect of material nonlinearity on the relationship between moment and curvature, the author wrote a program which can draw the M-φgraphic of a beam in different cross-section shape and different axis force. And the customizing of material model is supported in this program. In the program the cross-section has been equally divided into 11 stratum to ensure a high accuracy. In order to fix the definition range of the curvature, such principle was introduced: the strain of edge strata fiber not to beyond elastic limit. After axis force and limit strain is input, the definition range will be calculated automatically. And the definition range will be equally divided into 5 sections to get a M-φfold line.Through a series of geometric nonlinear analysis, it was found that the maxmum of the effect of geometric nonlinearity was 0.83%. In Chap.6 two simplifying method—single girder and twin girder was applied to analyse the vibration mode, and compare between the two method was made. Twin girder was found better in simulating the actual girder's bending stiffness in both rotating X dimension and rotating Y dimension. But it was also found serious distorting in simulating the actual girder's shearing stiffness, which due to twin gieder not well-simulating the function of the bridge deck, so that the FEM model having too large flexibility.