Analysis Of Stress Characteristics Of Structure And Bracket In The Construction Stage Of The Large-span Railway Middle-bearing Cfst Arch Bridge

In recent years,concrete-filled steel tubular Arch Bridge has been developed greatly because of its high bearing capacity,simple construction and beautiful appearance.But the application and research on the railway lags behind the highway bridge.With the increase of the span,cable hoisting construction combined with oblique pulling and hanging method has gradually become the main construction method of long-span arch bridges.However,the construction of the oblique pulling and hanging method is very difficult,and the force of oblique pulling and hanging system is very complicated.Therefore,it is very important to study the whole process of assembling arch rib with the oblique-pulling and hanging method.This thesis is based on the ZangMu Brahmaputra mega-bridge,which is a railway medium-bearing CFST arch bridge with a main span of 430 m,The Midas Civil Finite Element analysis program is used to simulate the whole construction process of the oblique pulling and hanging method according to the loading arch rib,the stress characteristics of the construction process are analyzed in detail.The main contents of this paper are as follows:1.This paper analyzes the key technology of cable hoisting and hanging in the large span arch bridge.Because of the large number of hoisting sections,the heavy section and the interaction between the sections,the difficulty of the linear control of arch rib increases,and the requirement of the lifting point elevation and the cable force calculation is higher.At the same time,the stress of construction tower and cable system should be analyzed more carefully.2.Because of the bad environment at the bridge site,the wind load and temperature difference are relatively large,so the cable hoisting construction is more difficult.By using the analytic theory and Finite element simulation method,the stress of 610 m cable system is calculated and analyzed.The stress and deformation of the crane structure are simulated and analyzed,and under the action of the most unfavorable wind loads,the maximum stresses and the deflection of the top of the tower are within the standard requirements.3.The Midas civil is used to simulate the oblique pulling and hanging system of the ZangMu mega-bridge.By using the unknown load coefficient method based on the influence matrix theory,the cable force of the cable is optimized and analyzed.Which makes the arch rib meet the design requirements under the buckle-hanging system,The displacement of the lifting point of each construction section and the cable force value of the buckle cable are provided.4.The stress characteristics of arch rib and buckle hanging system are analyzed in detail.Under the action of the most unfavorable wind loads,the stress and the top displacement of the tower structure are within the standard requirements,and the first-order stability coefficient of the whole structure is much greater than 4.0.Under the most unfavorable wind load,the maximum displacement of arch rib due to the deflection of the tower is up to 314.72 mm,the maximum displacement of the arch rib is up to 40.70 mm when the temperature difference reaches 20?,so it is suggested that the arch rib should be installed under the condition that the wind load and the temperature change are smaller.