Mechanical Characteristics And Parametric Analysis Of Steel Box-truss Composite Continuous Girder Bridge

The steel box-truss composite continuous girder bridge is a new type of structure developed in recent years,which is a combination structure of steel truss and steel box girder.This type of bridge makes the bridge structure have both the vertical stiffness of steel truss girder and the lateral stiffness of steel box girder,which can improve the overall mechanical performance of the bridge and reduce the mid-span deflection.Based on a proposed high-speed railway bridge,the bridge span layout is 72 m + 72 m.The finite element model of the whole bridge is established by using the finite element software MIDAS civil.The static and dynamic characteristics of this steel box-truss composite continuous beam bridge are calculated and analyzed,and the design parameters are studied.The main work and results include:1)This paper summarizes the development status and specific engineering examples of truss girder bridge and box-truss composite girder bridge at home and abroad,and puts forward the research significance and content of this paper.2)The static analysis of the bridge under the action of dead load,the most unfavorable live load,the main force and the combination of the main force and the additional force is carried out.The analysis contents include the reaction force of the support,the vertical displacement of the main beam,the internal force and stress of the truss member and the steel box girder.The elastic stability and dynamic characteristics of the bridge are analyzed,and the main failure modes and the first 12 modes of vibration under the dead load and the operating load of the bridge are analyzed.3)Analyze the design parameters of the truss in the steel box-truss composite continuous beam bridge.Analyze the changes in the truss height,inter-node length,web member angle of the equal-truss truss,and the truss height ratio of the middle and side fulcrums of the variabletruss truss.The internal forces and displacements of the bridge members in the completed state are analyzed.And summary.When the truss height is 12 m,the corresponding height-span ratio is 1 / 6 and the internode length is 12 m,the stress effect of the bridge structure is better.The angle of the web member is about 66 ° ～ 68 °,and the stress and deformation of the whole bridge are relatively better.The truss height ratio of the side and middle support points of the steel box-truss composite continuous girder bridge with variable height is 0.56.4)Based on the research of two-span steel box-truss composite continuous girder bridge,the influence of bridge parameters with 216 m full bridge length on the force of the bridge is further analyzed.This parameters include side-to-mid span ratio and steel truss layout range.The results show that the stress and deformation of steel box truss composite bridge are reasonable when the ratio of side to midspan is 0.786,and the stress of the whole bridge can be improved when the additional range of steel truss exceeds the midspan length.The research results of this paper can provide reference for the design of steel-box truss composite continuous beam bridge,and have certain engineering practical value.