Study On Structural Parameters And Shape Finding Of Bridges With Beam-string Structural System

Beam string structural bridge is a new type of bridge system based on beam string roof structure.With light weight,large stiffness of live load,uniform stress of main beam,convenient construction and transportation,the new system usually takes longitudinal beam string structure as the main force-bearing component,and transverse beam string structure as the force-transmitting component,which is the innovation and development of the traditional bridge structures.At present,the study of beam string structural bridge has not been in-depth,and there are no guiding opinions and suggestions for practical engineering application.Based on the existing researches,through comparative analysis,structure and connection details of the beam string structural bridge has been carried out,and mechanical properties under live loads have been studied,including live load stiffness,structural internal force,stability and dynamic performance.Complete optimization and shape finding methods of such system bridges are put forward.The main research work and achievements are as follows:1).Discussing and analyzing the principle and construction advantages of the beam string structure,from which the longitudinal and transverse layout forms are derived.Aiming at the key points and difficulties of the component connection,the cable structure analysis method is deduced.It shows that the initial internal force of the cable has little effect on the overall stiffness of the structure,the linear analysis can be satisfied,and the calculation model is simplified.2).Using the principle of control variables,the factors affecting the live-load stiffness and mechanical performance of the bridge with beam string structure are qualitatively analyzed.The analysis shows that the axial stiffness and sag of cable have great influence on the deflection and stress,and the influence decreases gradually with the increase of parameters;the number of struts has little effect on the structure,and can be reduced appropriately when meeting the performance requirements;the bending stiffness of the upper chord beam has little effect on the overall stiffness,but reasonable structural form can reduce the adverse effects of the whole structure caused by the local failure of the main girder.3)In order to ensure that the structure can meet the requirements of deflection,internal force and stability,greatly reduce self-weight and improve material utilization rate,the optimization of the beam string structural bridge is studied to make it more reasonable.At the same time,aiming at the linear difference between zero state and initial state,through shape-finding iteration,the lofting size of the structure construction is found,which provides a reference for the actual design.4)The buckling stability and dynamic characteristics of the bridge with beam string structure are analyzed.The results show that beam string structural bridge has superior mechanical performance and good economy.