Research On Reasonable Arch Axis And Stability Of Long-span Asymmetric CFST Arch Bridge

The asymmetrical arch bridge can adapt to the characteristics of the topography with a lower longitudinal section on one side and a higher side on the other side,making full use of the bearing capacity of the rock foundation,reducing the amount of excavation of the pier and abutment,saving engineering costs,and reducing the impact on the surrounding environment.The damage of the bridge has good applicability in the construction of mountain bridges.The concrete-filled steel tube arch bridge has light structure,beautiful appearance,large spanning capacity and convenient construction.It is widely used in long-span arch bridges.This paper mainly studies the selection of the arch axis of a large-span deck asymmetric concrete-filled steel tube arch bridge and the stability of the bridge in the completed state,and the following work has been carried out.(1)Briefly review the development of concrete-filled steel tube arch bridges,and analyze the structural characteristics and mechanical characteristics of asymmetric arch bridges.It is pointed out that the asymmetric arch bridge has obvious economic efficiency in mountainous areas with large terrain undulations and better geological conditions.(2)Introduce the commonly used arch axis forms of arch bridges,derive reasonable arch axis equations under different types of loads,and determine the arch axis coefficients.Combining the load characteristics of asymmetric arch bridges,the catenary is selected as the basic form of the arch axis.(3)Study the optimization method of the arch axis.For deck-type hollow arch bridges,the self-weight distribution of the arch structure is discontinuous,and the arch axis calculated by the five-point weight method is deviated from the self-weight pressure line,which often results in excessive internal force in some sections of the arch ring,so it is necessary to adjust the arch axis optimize.Through the comparison and analysis of various optimization methods,the linear combination method in the function fitting method is selected to optimize the arch axis of the asymmetric arch bridge.(4)Analyze the force of the main arch circle when the arch axis coefficients take different values when the rise-span ratio of the two half-archs is the same and the rise-span ratio is different.Through the force comparison under several situations,a more reasonable force state of the main arch is finally obtained,and then a reasonable arch axis equation is obtained through the optimization of the arch axis.Change the height difference between the arch feet on both sides of the bank and analyze its influence on the force of the main arch.(5)Calculate the stability of the asymmetric concrete-filled steel tube arch bridge.Through linear and non-linear buckling analysis,and considering different arch toe height differences,the change law of the stability of the arch ring is studied.