Dynamic Characteristic Analysis Of One Cable-Stayed Bridge

With the development of traffic construction in our country, long span prestressed concrete cable-stayed bridge has been widely applied in the field of road and bridge. Now, cable-stayed bridges are being designed to the direction of long span because of its cross ability and self advantages. Compare with other form of beam bridges, the cable-stayed bridges have their own dynamic characteristics caused by wind, earthquake and moving motor load. So it is important to search dynamic analysis of cable-stayed bridge. On basis of other people's work, this paper takes a certain cable-stayed Bridge for example and uses three dimension finite software-Ansys to study dynamic characteristic and response. Through the analysis of dynamic, it can reveal more truly the structure stresses and deflection under the effect of vehicles. The main contents and conclusions of this thesis are as follows:(1) The paper collected of cable-stayed bridges and dynamics, and recites the method for solutions in cable-stayed bridges structural dynamics and vibration characteristic of cables. Then take the example of a certain cable-stayed bridge, and introduce some kinds of simplified methods of 3-D space modal, establish 3-D finite element model of it with software ANSYS.(2) Research self-vibration of the bridge and detailed describe dynamic characteristic. And the effects on natural vibration of the subsidiary pies in the side spans and the boundary constraint condition and cross section stiffness of the cable tower are analyzed. The subsidiary pies have an apparent influence on the vertical stiffness of the bridge; Canceling horizontal displacement in longitudinal direction of bridge reduce the base frequency of the bridge; Increasing the stiffness of cable-stayed bridge towers can improve the natural frequency of the cable-stayed bridge.(3) During transient dynamic analysis, the time history responses of the structure under uniform velocity moving load are analyzed, The result indicate some conclusion as follows: The vibration of superstructure is fierceness and the higher moving speed the fiercer of the vibration.(4) Through a constant impact load of short duration at middle of the mid span, the time history responses of the structure under impact load are analyzed. And the amplification coefficients of deflection and bending moment of the girder and cable tension are intensively analyzed. The result indicate that when the phenomenon that uneven bridge floor causes vehicle jumping is unfavorable for the deformation of the structure, if value of coefficient of impact assume according to the current specifications in design of the cable-stayed bridge, some cross sections will be liable to unsafe.