Study On Mechanical Characteristic Of Curved Steel Open Trough Girder Under The Incremental Launching Construction Stage

In the construction of steel-concrete composite girder bridges using the incremental launching method,the steel trough girder section is first employed a push-out approach and during the construction phase,only the thin-walled open steel trough girders are subjected to alternating positive and negative bending moments,which may lead to greater adverse effects compared to the completed bridge phase.The curvature-induced "bending-torsional coupling" in curved bridges results in more unfavorable local stress and stability in the main girder compared to straight bridges.Therefore,it is of practical significance to study the force characteristics of bridges with different curvatures during the incremental launching construction phase.This paper focuses on the following:(1)Based on a real-life engineering scenario,the beam element model of the entire incremental launching construction process for bridges with different curvature radii is established using Midas Civil bridge finite element software.The most unfavorable construction conditions and force deformation differences for bridges with different curvature radii are determined.Then,ABAQUS general finite element analysis software is used to create a refined "shell-solid-contact" finite element model under the most unfavorable construction conditions for bridges with different curvature radii.The local stress response and stability differences of bridges with different curvature radii under the most unfavorable conditions are analyzed,and it is found that the stress of the steel trough girder bottom plate and web,as well as the lateral overturning stability,are sensitive to the change in curvature radius.Adverse effects increase when the curvature radius decreases to400m;the stress of stiffening components and diaphragms and the longitudinal overturning stability are not sensitive to the change in curvature radius.(2)The influence of different bearing parameters on the stress of steel trough girders is analyzed,revealing that bearing uplift has adverse effects on the local stress and lateral overturning stability of curved bridges.The local stress response to changes in bearing lateral height difference,pad length,and stiffness varies for different curvature bridges.Reasonable control values for pad length,stiffness,and lateral support height difference are obtained for different curvature bridges.(3)the influence of different incremental launching steps in the transverse and longitudinal directions of the same pier on the stress of different curvature bridges is analyzed,it is found that the main manifestation of the curvature’s impact on structural stress is the increase in concrete tensile stress at the base of the pier caused by the imbalance of support reactions on both sides of the same pier.When the curvature radius is greater than 600 m,the control thresholds for transverse and longitudinal horizontal forces can be considered as for straight bridges;when the curvature radius is less than 600 m,specific analysis is required.In any case,asynchronous longitudinal incremental launching on the same pier should be avoided.(4)Through comprehensive analysis concludes that when the curvature radius is less than 400 m,the structural stress,local instability,and overturning risk during incremental launching construction are significantly higher than those of straight bridges.Careful consideration should be given to the main girder parameters and incremental launching scheme.Through the aforementioned analysis and research,this paper not only directly serves the actual engineering background but also provides a reference for subsequent curved bridge incremental launching construction.