Stability Analysis Of CFST Ribbed Arch Bridge

Concrete filled steel tubular arch bridge is widely used in practical engineering because of its advantages of fast construction speed,good bearing capacity and large span capacity.But at the same time,some arch bridges with the characteristics of "large span,small ratio of width to span,no cross brace" appear the problem of lateral stability.Based on the engineering background of concrete-filled steel tubular arch bridge without cross braces,this paper establishes the finite element calculation model of this kind of arch bridge considering the nonlinear effe ct,discusses the initial geometric defects,the design difference of cross braces and the cross-section form of arch ribs,and calculates and analyzes the ultimate bearing capacity and reliability of the arch bridge without cross braces under the action o f each influencing factor.(1)In this paper,the basic theory of degenerated beam element and the three-dimensional finite element program csbnla based on the theory are introduced,and the nonlinear constitutive equation of materials considered in the pr ogram is analyzed.At the same time,on the basis of considering material nonlinearity,the U.L.formulation method is used for geometric nonlinear analysis.Then,in the nonlinear calculation,combined with csbnla finite element calculation program,the j udgment standard and analysis process of ultimate bearing capacity are studied.(2)Based on the project of Yilan Mudanjiang bridge,the peak defects in the range of L / 1000 ～ L / 600 are selected,and the live load multiple and safety factor of the arch bridge under the bearing limit state are calculated by using the consistent defect mode method and random defect mode method.It is revealed that the ultimate bearing capacity decreases with the increase of out of plane initial geometric imperfections.The influence of out of plane initial geometric imperfections on the mechanical behavior of CFST arch bridge is explored.(3)From the perspective of lateral stability,relying on Yilan Mudanjiang bridge,aiming at the problem of insufficient stability of the bridge in operation,this paper adopts the transformation method of adding transverse bracing,analyzes the effect of the number,stiffness and layout form of transverse bracing on improving the ultimate bearing capacity of the structure,and probes into the influencing factors of transverse bracing on the overall stability of the arch bridge.(4)Based on the response surface theory and the nonlinear finite element program csbnla,the response surface function of the stability ultimate bearing capacity of arch bridge is established.Then,through the calculation method of first order reliability,the variation law of ultimate bearing capacity reliability of concrete-filled steel tubular arch bridge without cross brace under different arch rib section forms is studied.