Theoretical And Experimental Study On Shear Stresses In Nonprismatic Composite Box Girders With Corrugated Steel Webs

As a new type of composite structure,the composite box girder with corrugated steel webs(CSW)has many advantages such as clearly defined forces,lighter self weight,high prestressing efficiency and good economic benefits,which has gained wide attention in bridge construction field.In order to make the structure lighter and reasonable,the structure of long span corrugated steel web is often replaced by the structure of trapped section with the further increase of bridge span.There are large differences in the force characteristics between the trapped section structure and the equal section structure,especially in the shear resistance of the steel webs.The assumption that the web bears all the vertical shear in the section no longer corresponds to the actual situation.There is a need for a further study on the calculation of shear stresses in non-prismatic CSW composite box girders.In this paper,a series of theoretical and experimental studies on the distribution of shear stresses in the non-prismatic composite CSW box girders are carried out through a large scale corrugated steel web-UHPC combination beam model test,combined with inductive statistics,theoretical analysis,experimental investigation,and finite element numerical analysis focusing on the distribution of shear stresses in non-prismatic CSW composite box girders.The main work includes.(1)The development history and structural characteristics of corrugated steel web bridges were systematically described,and the current application and shear resistance research of this new type of bridges were summarized.Taking the non-prismatic CSW combined box girder as the research object,the mechanics of materials method is adopted to take the variable-section microsegment for force equilibrium,and combined with the shear stress reciprocity theorem,a systematic and perfect theory of web shear stress calculation is derived,and a simplified formula is suggested according to the engineering needs.It is found that,unlike the equal-section beams,the shear stress of the non-prismatic CSW composite box girder is affected by the additional shear stresses generated by the bending moment and axial force due to the presence of "variable section effect".(2)A static load test of a large scale variable section CSW-UHPC model girder was designed and completed to simulate the typical stress condi tions during the construction of a large span combined girder bridge,and the static load tests were completed under different boundary conditions,different loading positions,different loading types and microcracks under a total of six working conditions,and the distribution of shear stress in each section and the variation law of bearing shear ratio along the span direction were obtained.The accuracy and applicability of the calculation theory were further verified by combining the spatial solid finite element model.And combined with the theory and test,the effect of the consistency of the action direction of bending moment,axial force and shear force on the law of shear bearing ratio of steel webs was obtained.(3)Using finite element software established the rod system model and refined solid model of the dependent project respectively.The whole process of construction of the bridge was simulated.The most unfavorable working conditions of the variable-section CSW composite box girder were analyzed under the combination of multiple effects such as self-weight,prestressing load,live load and shrinkage creep effect in the actual project,and the shear stress distribution law was derived.The design procedure of shear resistance of variable-section CSW composite box girder is also given from two aspects of shear strength and stability in combination with this dependent engineering and calculation theory,which provides a reference for the design of this sort of bridge.