Mechanics Characteristics Analysis On Cable-Stayed-Suspension Bridges

Cable-stayed-suspension bridge is a new combined structural system bridge as combination of cable-stayed bridge and suspension bridge.This sort of bridge has both merits of cable-stayed bridge and suspension bridge.Cable-stayed-suspension bridge has some special advantages especially under some circumstances such as bridge located at the soft ground or strong typhoons region.But there is only a little research on this sort of bridge in the world at present.Using the general finite element analysis software BNLAS,the space model of a bridge with main span of 1,692m was set up.Some major structural parametres have been analysed to find the effect of those parametres to the strcuture in this thesis.The thesis simply reviewed research of cable-stayed-suspension bridge in our country and abroad,then presented the mechanical feature of this sort of bridge.According to the two methods(the continuous beam with rigid supports method and minimum bending energy principle),the rational cable force of cable-stayed-suspension bridge was determined.By contrasting the rational cable force,the results show that the rational cable force determined by the two methods is similar.The internal force of the girder by dead load has been analysed.The internal force and deflection of the girder by live load has been analysed.The influence line of structure has been analysed. Some major structural parametres such as the stiffness of the girder and the tower, rise-span ratio,ratio of side span to center span,piers in the side-span, kinds of structural system were analysed to find their effects on internal force, deformation and horizontal tension of main cable produced by the live load and by the seismic.The coordination of the stiffness in the joint area has been analysed.Through analyzing mechanical feature of cable-stayed-suspension bridge,the thesis find that horizontal tension of main cable is lower than the suspension bridge over the same span.So the cost of cable and anchor can be reduced much.Cause the effect of the part of cable-stayed bridge,cable-supspended bridge has better properties of stability.By means of comparing the effect of major structural parameters,the results show that improving the stiffness of the girder or increasing the number of the piers in the side-span can improve the mechanical properties effectively,can improve the coordination of the stiffness in the joint area and can improve the stiffness of the structure. Through the analyzing and discussion above,some constructive suggestions on the design were gained.