Study Of Mechanical Property And Calculation Method Of Shear Lageffect In Truss Girders With Integral Orthotropic Deck Of Suspension Bridge

The development of long-span suspension bridge hasn’t run its full course, along with the rising of its span, the percentage of dead load in all loads is further increased, which will put forward higher requirement on designing, manufacturing and erecting main cable and stiffening girder. Using of truss girders with integral orthotropic deck can alleviate dead load of structure effectively and simplify bridge deck system of suspension bridges with steel truss beam. However, this kind of structure is seldom used in suspension bridge, thorough cognition and study of it hasn’t been reached; in addition, it has complex constructs, lots of components with orthotropic plate criss-cross distribute in the structure, further study should be made of how to simplify this kind of structure. To address this problem, this article mainly makes study of truss girders with integral orthotropic deck in the following ways:(1) Truss stiffening beam with different kinds of joint types has been calculated and analyzed to study the difference of structural behavior in bridge deck system with stiffening girder between plate-truss conjunct and isolate; By means of analyzing the mechanical property of stiffening girder in truss girders with integral orthotropic deck with different support formulas bearing loads of system one and deck loads, reasonable structure and mechanical property of truss girders with integral orthotropic deck has been studied.(2) Calculation method of equivalent shearing thickness in normal truss has been introduced to analyze truss girders with integral orthotropic deck in suspension bridge, a program of continuum modeling of truss girders and geometric-nonlinear analysis in plane frame system has been crafted. The influence of rigid joint and shear deformation to structural internal force and displacement has been discussed. And the reasonable simplified calculation model in overall calculation of truss girders with integral orthotropic deck suspension bridge has been obtained.(3) The discipline of shear lag effect in truss girders with integral orthotropic deck along the whole suspension bridge has been obtained; longitudinal displacement differential functions are discussed based on it. On the basis of continuum modeling of truss girders, analytic solution of simply supported beam bearing uniform load and concentrated load has been deduced by variational methods, analytical method of shear lag effect based on discrete hanger forces and bending moment influence area has been proposed, and its influence factor has been discussed(4) In consideration of limitation of variational method, this article has deduce detailedly elastic rigidity matrix and geometry rigidity matrix of beam element in consideration of shear deformation and shear lag effect, which is based on energy approach and incremental virtual work equation, and a program has been crafted, its accuracy has been verified by contrasting the result obtained from ANSYS.(5) Through this research, loading features of truss girders with integral orthotropic deck with stiffening girder, the reasonable simplified model using continuum modeling of truss girders and the method of calculating shear lag effect has been obtained, the study of this article shows that: stiffening girder of truss girders with integral orthotropic deck bears complex forces, different kinds of simplified models should be selected according to its loading features in calculating and analyzing; computational accuracy of overall calculation will be improved by using continuum modeling of truss girders because it considers the impact of rigid joint and shear deformation. Analytical method of shear lag effect based on discrete hanger forces and bending moment influence area mentioned in this article is clear in physical conception, easily sequence and highly accurate when solving shear lag effect of stiffening girder in suspension bridge, but it is limited in solving differential equation. It is convenient to solve shear lag effect with complicated longitudinal displacement differential functions by using single-dimensional finite element method of shear lag effect, mentioned in this article which is based on interpolation function.