| The calculation methods of the bridge structure reasonable construction state generally are forward iteration method,the backward analysis-forward iteration method and the unstressed state method,Compared with the forward iteration method and backward analysis-forward iteration method,unstressed state method can effectively avoid the influence of temporary load and temperature load in the construction process,simplify the construction process and improve the construction efficiency to a certain degree.However,the unstressed state method is mainly used in the construction control of cable-stayed Bridge,and rarely used in steel box tied arch Bridge.In this paper,the application of the unstressed state method in the steel box tied arch bridge with a span of 120 m is studied.The main work of the paper is as follows:(1)The present research status of the unstressed state method is described,and the importance and necessity of expanding the application scope of the unstressed state method are explained in this paper.(2)According to the basic principle of the unstressed state method,taking the simplified tied arch bridge as an example,this paper discusses the basic principle of the application of the unstressed state method in the steel box tied arch bridge,Based on this,the idea of applying unstressed state method to steel box tied arch bridge is put forward.(3)According to the application idea of unstressed state method,The reasonable completion state of the bridge is determined by using rigid supported continuous beam method,minimum bending energy method and rigid suspender method,and three completion states are compared.The results show that the minimum bending energy method is more reasonable.(4)Based on the target completion state,the unstressed length of suspender corresponding to the target cable force is calculated by using the finite element software MIDAS civil,and the internal force state of the bridge completed in stages and once is compared.The results show that the two states of the bridge completed are basically the same,and the construction control is feasible with the unstressed length as the control target.By analyzing the calculation method of unstressed linear of arch ribs and the unstressed linear of tie beams,it is found that the calculated unstressed linear can be converted into the calculation of the pre-camber of the structure,and the unstressed linear of arch ribs and the unstressed linear of tie beams are determined.(5)Combining the determined unstressed state quantity,calculate internal force state and linear shape change during the construction of the bridge,And compare the completed bridge state calculated by forward iteration method and backward analysis-forward iteration method and the unstressed state method,the results show that the construction state determined by the unstressed state method is safe and reliable,The completed bridge status obtained by the three calculation methods has a small difference.The unstressed state method is suitable for determining the reasonable construction state of this bridge.compared the measured and calculated values of the arch ribs,tie beam linearity and the suspender cable forces after the bridge is completed,the errors are within the allowable range of the code.It is verified that the unstressed state method can be applied to the steel box tied arch bridge,which provides reference for the construction and calculation of similar bridges. |
