The Research On Construction Control Of Steel Box Basket Arch Bridge With Buckling Tower

The steel box basket arch bridge with the combination of buckle and cable tower is a special case of construction by inclined pull buckle and cable hoisting method.It combines the buckle of the inclined pull buckle system with the cable tower of the cable crane system for construction,but this will lead to the mutual influence of the two systems and increase the difficulty of construction control.Based on the engineering background of Chetianjiang Bridge in XinHua,Hunan Province(hereinafter referred to as the bridge),this paper establishes a finite element model based on Midas software,studies the construction control of the bridge,and implements the research results to the field monitoring,which ensures the efficient and high-quality completion of the bridge from the perspective of construction monitoring.The main research contents of this paper are as follows:(1)The engineering background of the bridge and the establishment of its finite element model are introduced in detail.The common calculation methods of the buckled cable force and the calculation process of the buckled cable force and the stress-free length of the suspender are summarized.Several arch rib alignments in the construction process of arch bridge and their relationship are introduced.At the same time,Midas is used to calculate the pre-camber value after deducting the influence of hinged displacement of arch rib segment,so as to determine the installation alignment of the bridge.(2)On the basis of the established finite element model,the arrangement number of temporary transverse braces is optimized,and the differences between the arch rib and the buckle tower in the construction process before and after optimization and the influence of construction stability are compared.Finally,it is found that the optimization of the number of temporary transverse braces has little effect on the stress state in the construction process,and the influence on the alignment can be corrected by adjusting the pre-camber value of the arch rib and the back cable force,and the arch rib construction process after the optimization of the number of temporary transverse braces still has sufficient stability.(3)The demolition process of the buckled cable and the installation sequence of the main girder of the bridge are analyzed.The Midas software was used to set up four cable removal processes and three main girder installation sequences,and the changes of arch rib displacement,linear and cable force in the construction process under different sequences were compared.The analysis results show that the sequence of removing buckled cables from top to bottom has the least comprehensive influence on the bridge state in the process of removing cables.After analyzing the influence of the installation sequence of the main beam,it is found that the construction scheme of rotating and installing the steel main beam from the middle and side spans has the least influence on the arch rib alignment.(4)The importance of construction control in bridge construction is expounded,and the construction monitoring scheme of the bridge is briefly introduced.The method of calculating cable force through the fundamental frequency of steel cable vibration is discussed,and the difference between the calculation results of different formulas and the theoretical value is compared.It is found that the modified cable force calculation formula has better applicability.Finally,the linear and cable force monitoring results of the bridge at the completion stage are given,and it is concluded that when the suspender is less than 15 m,the measured cable force value is generally larger.