Application Of The Stress-free State Method In Construction Control Of Steel Truss Arch Bridge

Steel truss arch bridge has many members and complex structure,so it puts forward high requirement for bridge construction control.The stress-free state control method takes the stress-free state quantity as the control parameter,which can directly establish the relationship between the construction intermediate state and the completed bridge state,and can well solve the problems of large calculation workload and low construction efficiency.Based on the stress-free state method and taking the practical engineering as the research background,this paper mainly completed the following research work.(1)In order to apply the stress-free state method to the construction control of steel truss arch bridge successfully,the basic principle of the stress-free state method was discussed,and the general balance equation of staged forming was established.Based on the finite element model,the applicability of the minimum bending energy method,the influence matrix method and the zero displacement method in determining the reasonable completion state of steel truss arch bridge was studied.The reasonable completed bridge state determined by the influence matrix method with the rod force as the control parameter was regarded as the target completed bridge state.Finally,on the basis of the target completed bridge state,the stress-free state quantity of the component was calculated.(2)The ideal construction state was established by using the stress-free state method,reverse disassembly and forward installation iterative method and forward installation iterative method,and the advantages of the stress-free state method in construction control of steel truss arch bridge were explained.Based on the stress-free state method,the suspender tension sequence was optimized and analyzed.On the basis of the ideal construction state,the ideal construction intermediate state of arch rib,tie beam and coupling member was determined.(3)According to the influence of different parameters on the structure,based on the finite element model,the sensitivity of relevant parameters was studied,and the sensitivity factor and sensitivity percentage of each parameter were obtained by using the response surface method,and each parameter was divided according to the importance degree according to the sensitivity percentage.(4)It was found that the temperature difference between the construction stage temperature and the design temperature would cause the change of the suspender secondary tension.Therefore,three correction methods were proposed,and the correction effects of the three correction methods were compared and analyzed.It was concluded that the suspender secondary tension correction method based on the stress-free state theory had the best effect,and this formula was verified.(5)Based on the finite element model,this paper analyzed the influence of arch rib construction error,suspender installation error and suspender tension error on the internal force and alignment of the structure,and put forward the construction error correction method based on the stress-free state method.(6)In view of the fact that the suspender force of the steel truss arch bridge in the actual completed state was not consistent with the target suspender force,and it was difficult to accurately measure the stress-free length of the suspender force in the actual completed state,this paper proposed a suspender secondary cable adjustment method based on the stress-free state method,and compared it with the influence matrix method to illustrate the applicability of this method.