Study On The Dynamics Of The Temporary Cable-arch Structure Of The Long Span Arch Bridge During Cable Hoisting Construction

At present,the cable hoisting method is a very important construction method for long-span arch bridges.During the construction,the cable and the main arch are combined into a temporary cable-arch structure by means of diagonally pulling and hanging.With the advancement of the construction process,the number of components will increase,the structural system will become softer,and the stiffness will decrease.Because the bridge span structure did not form a final system during the construction phase,the stiffness,stability and safety of the cable-arch structure were much lower than the final system.At this time,the vibration of the cable-arch structure will seriously affect the safety,quality and precision of the construction.It is a huge safety hazard and reduces the safety factor.Therefore,it's power problem is worthy of attention.In this paper,the construction process of cable hoisting of large and small well bridge(main span 450m)is taken as the engineering background,and the in-plane natural vibration characteristics and dynamic response analysis of typical cable hoisting sections are analyzed by finite element software.The main research contents and conclusions are as follows:(1)On the basis of the existing literature,to understand the characteristics of the cable-arch structure and the nonlinear influence,summarize the basic theory of the cable-arch structure dynamic analysis in the construction stage,and determine the analysis content and research methods.According to the research status of cable-arch structure at home and abroad,it is concluded that the cable-arch structure deserves further attention during the construction process.(2)Based on the engineering background bridge,the distribution characteristics of the induction cable-arch structure and the corresponding frequency are analyzed,and the main parameter intervals of structural resonance are found.The localization degree parameter is introduced to quantitatively describe the vibration mode of the structure numerically.The effects of cable tensile strength,main arch stiffness and boundary conditions on structural modal distribution are analyzed.The results show that the cable-arch structure has both the local vibration mode of the cable and the overall vibration mode of the structure,and there is a possibility of internal resonance between the modes of different orders.As the hoisting segment increases,the structure will be more susceptible to overall vibration.The stiffness and boundary conditions of the main arch play an important role in the overall vibration mode distribution of the structure.The tensile strength of the cable has no effect on the overall vibration mode distribution of the structure.(3)By analyzing the dynamic response of typical cable-arch structure under cyclic loading,the effects of different load frequency,load amplitude,load position and damping on the dynamic behavior of the structure are analyzed.The results show that when the load frequency and the first-order overall vibration mode frequency ratio of the cable-arch structure are about 1:1(0.98?1.02),the overall vibration of the cable-arch structure will occur,and the structural displacement and internal force value will increase rapidly.With the increase of the load amplitude,the displacement and internal force amplitude will increase when the structure resonates;when the load action position is different,the structure will produce displacement and the internal force amplitude will be greatly different.It is necessary to pay attention to avoid the unfavorable position of some loads during construction;As the damping increases,the displacement and internal force amplitude will decrease.