Analysis On Stability Of Long-span Tied Concrete-filled Steel Tubular Arch Bridges

As Concrete-filled steel tubular arch bridge can resolve the contradiction between the erecting weight and span length, it has become one of the bridges which develop the most rapidly in recent years. However, compared with the engineering practice, its design theories are relatively backward. Due to small width-span ratio, the relative stiffness of the long-span concrete-filled steel tubular arch bridge is weak.Therefore, the stability of concrete-filled steel tubular arch bridges is becoming increasingly important. Research on it is of great importance both in theory and engineering value.Stability problems are usually divided into two categories:the branch point destabilization based on the linear elasticity and the extreme point destabilization considering geometric nonlinearity and material nonlinearity. In practical engineering, dead load pressure line of arch bridges will deviate from the arch axis line. Furthermore, the construction of camber settings, the initial deformation caused by construction deviation, asymmetric loading and other factors make the actual destabilization largely belong to the second destabilization, that is, the extreme point destabilization.This paper elaborates the theory related to linear and nonlinear stability, and discusses various methods for solving non-linearity. By adopting a general-purpose finite element analysis software, the paper also analyzes the linear elasticity, geometric nonlinearity and double nonlinearity of a concrete-filled steel tubular arch bridge with a span of 125+125m. In double non-linear analysis, only the double nonlinearity of the arch ribs was considered. In other elements, only the geometric nonlinearity was considered. The calculating results show that the safety factor of linear elastic analysis is clearly large, it may generate non-safe results; the geometric nonlinearity has slight effect on stability; stability coefficient caculated by double non-linear method is far less than the factors caculated by linear elastic method or geometric nonlinear method. This paper concludes that the double nonlinearity must be taken into account in analyzing the stability of concrete-filled steel tubular arch bridges.Finally, It analyzed the influences caused by the number and layout of cross brace,restraint effect of core concrete and initial defects. The calculation results and conclusions have some reference value for the future design of concrete filled steel tubular arch bridges.