Research On Geometric Nonlinear Non-destructive-Fitting Closure Of Cantilever Casting Arch Bridge

The reinforced concrete arch bridge has the advantages of large bearing capacity,clear force state and reasonable economy.As the arch bridge develops in the direction of the large span,the construction method is also constantly developing in the direction of adapting to the construction of the large span arch bridge.Cantilever pouring construction is a commonly used method for long-span arch bridges.Based on the stress characteristics of cantilever-casting arch bridges,the geometric nonlinearity problem during construction is becoming more and more obvious.Compared with the linear state,the internal force and deformation are more complicated.Therefore,the strict control of the buckle force in the construction process considering geometric nonlinear factors is of great significance to meet the target state of the bridge and the safety performance of the construction.This paper carries out the following work:(1)Focus on the research status of the cantilever pouring construction arch bridge,the reasonable establishment of the bridge and the determination principle of the construction state.Aiming at the reasons and research results of the current collapse of the long-span bridge structure,it is proposed that the cable force,the internal force of the arch ring and the linear closure of the cantilever-casting arch bridge considering the geometric nonlinearity need further study.(2)Determining the method of determining the construction state of the arch bridge and the correlation with the closedness calculation of the inverted assembly,analyzing the substantial reasons for the unclosed dressing considering the geometric nonlinearity and comparing and summarizing the current calculation method for the inverted assembly..Based on the reasonable arch axis optimization theory,the reasonable arch axis of the bare arch is determined by the case,and an improved reasonable arch axis-suspension line is introduced.(3)The research progress of geometric nonlinear theory of arch bridges,geometric nonlinear influencing factors and finite element analysis and calculation methods are introduced.Introducing the Ernst formula and catenary theory,using Ansys to consider the sag effect of the cable;establishing the relationship between the P-delta effect and the geometric stiffness in the beam-column effect;and compiling the Matlab program considering the large deformation effect according to the Riemann integral and the dichotomy;It is proposed that the geometric nonlinear iterative calculation using the UL formula is more in line with the calculation method of the construction process;(4)Determine the force state of the maximum cantilever state of the cantilever cast arch bridge by the method of bending moment return to zero.Based on the linear calculation of small deformation and the iterative calculation case under large deformation effect,the linear and geometric nonlinear inversion-assembly results are obtained respectively.The analysis shows that the UL column method under certain iteration step is to satisfy the geometric nonlinearity.Demolition-formal loading calculates the conditions for closure.General discussion and case analysis of the stress-free state method,verifying that the structural system is invariant,and that any stress state transitions independently of the process;(5)Using the Fuling Wujiang Bridge double-track bridge to establish the finite element calculation model,consider the influence of three geometric nonlinear effects on the cable force,the internal force and displacement of the arch ring during the construction process,and discuss the UL iteration under certain iteration steps.The geometric nonlinear non-destructive formal closure results of the method verify the condition of the closedness of the inverted assembly considering the geometric nonlinear factors.