Study On Ultimate Bearing Capacity Of CFST Arch Bridge Considering Initial Stress And Initial Defect

As a combination structure,the concrete-filled steel tubular arch bridge has fully played the good performance of the steel and concrete,and the two materials are complementary and complement each other,which is one of the rapid development structure system in recent years.The light of the material and the maturity of the construction system make the bridge engineers pursue a larger span bridge structure.With the increase of the span,the stiffness of the whole structure is reduced,and the ultimate bearing capacity of the bridge needs further study.For the structure of Cfst Arch Bridge,the hoisting of empty steel pipe and the pouring of concrete will cause the ste el pipe to be loaded before the composite structure of concrete,and the initial stress will be produced,at the same time,because of the position deviation in the process of steel pipe fabrication and hoisting,will make the concrete filled steel tubular arch bridge have the initial geometrical defect before forming the bridge.Preliminary stress and initial defects will have a certain impact on the ultimate bearing capacity of CFST arch Bridge,this paper analyzes the ultimate capacity of arch bridge wit h two kinds of factors,which is based on the concrete-filled steel tubular arch bridge with a limb lattice structure,mainly completes the work:First,the ultimate bearing capacity of CFST Arch Bridge is discussed and analyzed: The problem of solving the ultimate bearing capacity of long-span structures usually boils down to solving the second stability problem and solving the second kind of stability problem,the material nonlinearity and geometrical nonlinearity of the structure should be considered at the same time,and the constitutive relation of steel and concrete is selected.The theoretical calculation of ultimate bearing capacity of CFST arch Bridge Considering initial stress is analyzed,and the ultimate bearing capacity of concrete-filled steel tubular arch bridge is analyzed.Secondly,the finite element numerical simulation is used to the model of concrete-filled steel tubular arch bridge with limbs is established,the ultimate bearing capacity coefficient under different initial stress is analy zed,the ultimate bearing capacity of the structure can not be more than 10%,the initial strength cannot be greater than 0.4,The greater the slenderness ratio,the effect on ultimate stability bearing capacity of CFST arch bridge with initial stress is a lso greater.According to the coefficient of ultimate bearing capacity under different steel-bearing ratio,the higher the steel ratio,the greater the ultimate bearing capacity coefficient,the 8%-12% of the ultimate bearing capacity under steel-bearing ratio 7% The growth rate of the ultimate bearing capacity coefficient under steel-bearing ratio is between 0-17%,the higher the steel-bearing rate,the higher the growth rate;from four kinds of steel models of the ultimate bearing capacity of the comparis on found that,compared to Q235,the other three types of steel models under the ultimate bearing capacity coefficient of growth in 10%-25%,the higher the strength of steel,The higher the ultimate stability bearing capacity coefficient is,the greater th e growth rate under C50 than the two concrete grades of C60 and C55 shows that the influence of concrete grade on the ultimate bearing capacity of CFST a rch bridge is relatively small.The double nonlinearity must be considered in the design of Long-span bridge structures.Finally,the ultimate bearing capacity of CFST arch Bridge considering initial geometrical imperfection is analyzed:the initial geometrical defects of different arrangement and different size are applied to the surface and exterior of arch structure,and the influence of initial imperfection on ultimate bearing capacity is studied.The calculation result is that the initial defect in the plane has a greater influence on the ultimate bearing capacity than the initial defect outside the surface.At the same time considering initial stress and initial defect,the ultimate bearing capacity of the structure should be reduced to less than 10%,the initial force should be controlled within 0.3,and the original geometrical defect control within L/5000 is the most suitable.