The Study Of Effect On Capacity Of Circle CFST Arch With Steel Tube Initial Stress And Testing Program

In the last 20 years, The CFST has been widely adopted in the arch bridge building. In construction of long-span arch bridge, the main methods are non-bracket construction technology or the swing technology. Under these methods, before the formation of CFST arch bridge, steel tube will withstand the weights of itself and the wet concrete; this will cause the initial stress of the steel tube inevitably. The initial stress forces the steel tube to prior reach the yield point of material, which will affect the bearing capacity of CFST arch bridge.This paper considered the initial stress in the calculation of the CFST arch bridge's bearing capacity, at the same time in order to verify the accuracy and reliability of computing, purposeful design the model experiment which considered the initial stress on the mechanical properties. Main research works are as follows:①. Based on spatial beam element nonlinear geometry equation, explicit tangent stiffness matrix of spatial beam element contained the initial stress and the initial strain in general elastic configuration relationship has been applied. Laid the theoretical foundation in studying the initial stress on the ultimate bearing capacity of CFST arch bridge.②. Based on collecting and summarizing the constitutive relation of CFST, select the constitutive relation of the steel and concrete reasonable, the computation of ultimate bearing capacity of CFST arch bridge will be completed by spatial beam element.③. The ultimate capacity and the influence factor K p of single-tube CFST arch bridges including different initial stress factorβ, span and rise-span ratio as well as sectional steel ratioαhave been performed. The analytical results show when bearing capacity analysis of steel tube initial stress to CFST arch bridge was performed, both material nonlinear and geometry nonlinear should be simultaneously included; steel tube initial stress can reduce bearing capacity of CFST arch bridge. However, the reduced extents have connection with steel tube initial stress factorβ, rise-span ratio, sectional steel ratioαand span etc. If the reduction extent of bearing capacity does not exceed 10%, thus initial stress factor of single-tube CFST arch bridge should be limited to 0.2.④. By studying the ultimate bearing capacity of single-tube CFST arch bridge which considering the steel tube initial stress, application the theory of least square method, the formulas of bearing capacity influence factor under different span and rise-span ratio have been given for single-tube CFST arch bridge by use of MATLAB.⑤. To verify the theoretical calculation, design two models of single-tube CFST arch bridge, one is single point loading on vault; another one is single point loading on one quarter of span.⑥. For the two models, the ultimate capacity analysis of single-tube CFST arch bridges span as well as sectional steel ratioαhave been performed. The results show that the model arch bridge loading on vault compared the single point loading on one quarter of span; the ultimate capacity and the influence factor K p are larger.⑦.The whole model test process were designed, For the later model test successfully, it provide methods and means.