The Influence Of Lateral Brace On Mechanical Performance Of Super Long-span Concrete-Filled Steel Tubular Arch Bridge

As the increasing demand of the bridging ability of the bridge,its out-of-plane instability gradually stands out.The lateral brace,as the transverse linkage,can connect the arch ribs into spatial structure,which efficiently improves the out-of-plane stability of the concrete-filled steel tubular(short for CFST)arch bridge.Therefore,it will have an influencial significance on improving the out-of-plane instability if the regularity of the lateral brace on structural mechanical performance can be mastered after research.For this purpose,the study has been carried out by researching on the influnce of the lateral brace on the mechanical performance of a 500-meter class super long-span CFST arch bridge.The spercific research content and major conclusion is summarized as follows:(1)Combined with the basic theory as well as the solution steps of finite element method and project overview of the Zangmu Yalung Tsangpo River Super Long-span Bridge(short for Zangmu Long-span Bridge),the finite element software Midas/civil 2015 has been used to model the spatial model of Zangmu Super Long-span Bridge and the actions such as dead load,live load and wind power,are calculated,which lays the foundation for the subsequent research work;(2)By changing the types of lateral brace at the arch crown and the springer,the internal force and displacement of the structure are calculated under the combination of the most unfavorable lateral loads to analyze the influence of the lateral brace types on the static performance of the structure.The research indicates that the “?” shaped lateral brace should be arranged between the springer and 1/4 span to improve the lateral stiffness and the flexural rigidity of the structure,while “X” or “?” shaped lateral brace arranged between 1/4 span and the crown vary little on improving the static performance of the structure.(3)Taking the natural frequency and vibration mode of the structure as the research object,the subspace iteration method of eigenvalue analysis is used to analyze the positions,numbers,types and stiffness of the lateral brace of the Zangmu Super Long-span Bridge and the law of natural characteristics of the structure under different lateral brace varieties is obtained.The research shows that the “?” shaped lateral brace should be arranged between the springer and 11/32 span to increase the out-of-plane and torsional vibration frequency,while the influence of “?” or “?” shaped lateral brace arranged between 11/32 span and the crown on the vibration frequency is close;therefore,“?”shaped lateral brace is recommended to decrease the construction difficulties.(4)Taking the structural stability safety factor as the research object,using the eigenvalue buckling analysis function,the single-factor analysis is carried out by analyzing the positions,numbers and types of the lateral brace of the Zangmu Long-span Bridge,and the variation law of structural stability safety factor under different lateral brace varieties is obtained,with the load condition being self-weight and the second-stage dead load.The research suggests that the “?” shaped lateral brace arranged between the springer and 11/32 span would sharply increase the stability safety factor of the structure,while the influence of “?” or “?” shaped lateral brace arranged between 11/32 span and the crown on the stability safety factor is close;therefore,“?”shaped lateral brace is recommended to decrease the construction difficulties.