Study On The Construction Line Control Of Large Section Steel Box Girder

The steel box girder has been widely used in bridge construction;however the popularization remains restricted by transportation,hoisting or site environment factors.The steel box girder rarely been processed at the scene of construction site.In particular,steel box girder with large section is processed by professional factory,then splited into each unit and transported to the construction site.The steel box girder will be installed in presupposed position by pre-combination,lifting,pushing,hanging,and welding.While the stress state can be influence by the inevitable deflection in each stage.In order to effectively control the deformation of each stage,this paper takes steel box girder bridges of Chuanshan-Haosifang Highway for example,it explains the key points and phases of the whole process including they are segmented longitudinally and sectioned transversely at workshop,transported to site,assembled into suitable lifting units,installed by large crane,welded into closure shape.This article also included some contents of welding and weld joint in steel box girder construction.The research is as follows:(1)In the article,the application of steel box girders in bridges is reviewed.The existing problems in the process of construction of steel box girders are summarized.Then the research content and technical route of this article are proposed.(2)The steel box girders in Daqi interchange main bridge of Chuanshan-Haosifang Highway are analysed as the research background.The steel box girder and its theoretical deformation are analysed by finite element simulation.Construction process and construction deformation control are researched combined with specific engineering with the consideration of steel box girder with large section.(3)The control methods of fabrication deformation of steel box girders with large section are researched.Basedon the structure details of steel box girders with large section,block forms of plate element and manufacturing control points are selected.Main points of the beam manufacturing control are proposed combined with the beam section processing technology.Considering the characteristics of unit assembly,reasonable welding process and welding sequence are analysed in order to control the welding distortion and fabrication deformation in the factory.(4)The temporary trestle deformation of steel box girders with large section are researched.The static load deformation,the overall stability,the anti-overturning performance,and the stress and deformation control of the local structure are analyzed by finite element simulation method,which aims to provide theoretical basis for the control of the temporary trestle deformation.The results show that the maximum vertical displacement of the temporary support is less than 3mm.The lattice structure and the single row temporary bracket both meet the stability requirement,and the range of the high stress zone of the temporary support,the distribution beam and the temporary support is small,near the contact point.(5)Combined with the real bridge engineering conditions,alignment control methods of the block erection sequence of steel box girders with large section are researched.Engineering condition,sequence and processof hoisting are analyzed in details.Rationalization and safety of lifting eyes of hoisting units are studied.Technical requirements for assembly and measurement scheme of steel box girder lifting are refined.Besides,welding quality of field welding are studied with different control methods.Detailed allowable value of welding deformation and controlling factor of field condition are given as a conclusion.