Conceptual Design Of Rail-cum-road Cable-stayed Suspension Bridge With 1736 Meters Main Span

The rail-cum-road bridges can make more scientific use of resources and save investment in the construction process,which will play an important role in the future.However suspension bridges and cable-stayed bridges,which are commonly used cable-supported bridges,have some shortcomings in the construction of long-span rail-cum-road bridges.The cable-stayed suspension bridges,which conbine the characteristics of the suspension bridges and cable-stayed bridges,is a competitive structure of rail-cum-road bridges.In this dissertation,the conceptual design,static and seismic response of the Rail-cum-road cablestayed suspension bridge are studied and the main technical difficulties are summarized,which provides a reference for the design of such bridges.The specific contents of the work are as follows:1.After reading a large number of related literatures and summarizing the previous research results,the appropriate parameters are determined according to the design requirements,and the conceptual design of a rail-cum-road cable-stayed suspension bridge with the 1736 m main span is completed.The main girders of the two schemes are single-layer mixed box girder and double-layer steel truss girder respectively.2.The finite element software BNLAS is used to establish the whole bridge model and determine the reasonable completion state of the two schemes respectively.Based on this,the internal force and stiffness characteristics of the two schemes under dead load,live load,service load and the fatigue behavior of the hangers and cables are analyzed,and the strength and stiffness of the structure are checked according to the requirements.3.The full bridge model is established by finite element software ANSYS.The free vibration characteristics and flutter stabilities of the two schemes are studied.Based on response spectrum method,the responses of the structures under earthquake are analyzed.4.The comparative analysis of the static and dynamic characteristics of the two schemes shows that the strength of each component of the two schemes under operation stage and earthquake action and the overall stiffness under the operation load can meet the design requirements,and the first-order torsional frequencies are large,which are beneficial to wind resistance;however,but the fatigue problem of the cables and hangers in and near the overlap area especially for the longest hanger is prominent.and the negative reactions of the two schemes at the operational stage are large,which requires further optimization design.