Study On The Closure Technology Of Large Span Continuous Steel Truss Girder Bridge With Flexible Arch

The flexible arch combined large-span continuous steel truss girder bridge type has been widely used in the construction of the domestic new railway bridges recently owing to its features such as large vertical stiffness,high carrying capacity,superior spanning capability,short construction period and beautiful exterior.Domestic researches on steel truss girder bridge start late,among which few topic is working on the technique of these bridges’ closure,so there is no single one closure control system for these bridges which is mutually acknowledged.Based on the Guanhe super large bridge on the routine of the lian-yan railway,this paper focuses on techniques of closures for the parallel chords and the flexible arch.Main works are as follows:(1)Based on the engineering information,the construction plan & characteristics of the Guanhe super large bridge and the references of the closure technique from similar bridges,the main contents of closures for the parallel chords and the flexible arch are analyzed and a FEA model with the bridge construction stages considered is established.(2)Specific measures for reinforcing the construction stability,i.e.the anti-overturning stability of the steel truss girder,the global and local stability of the parallel chords prior to its closure,are put forward,aiming at facilitating the closures for the parallel chords and the flexible arch.(3)Based on the difficulties in the closure of parallel chords,several measures for adjusting the position of the to-be-closed parallel chords are selected to conduct sensitivity analysis.The continuous monitoring data prior to the parallel chords’ closure is sorted and analyzed.With all of the results above,a technical plan is put forward for realizing the optimal closure for the parallel chords of the Guanhe super large bridge’s steel truss girder.(4)Based on the difficulties in the closure of flexible arch,several measures for adjusting the position of the to-be-closed arch chords are selected to conduct sensitivity analysis.The continuous monitoring data prior to the flexible arch’sclosure is sorted and analyzed.With all of the results above,a technical plan is put forward for realizing the optimal closure for the parallel chords of the Guanhe super large bridge’s steel truss girder.The results show that,i)the construction control and continuous monitoring prior to the closure together with the sensitivity analysis for the to-be-closed chords are the three major contents for the closure control of the parallel chords and the flexible arch,ii)the advanced construction control is the most crucial one to the optimal closure,calculations should be done to learn about the anti-overturning stability of the steel truss girder as well as the global and local stability of the parallel chords in the structural maximum cantilever stage,and measures should be taken to ensure the wind resisting stability of the suspenders,iii)the sensitivity analysis for the to-be-closed chords is conducted for selecting the optimal closure adjusting measures,and the continuous monitoring prior to the closure is conducted for determining the optimal closure temperature and time,both of them are important to the optimal closure plan.The practice proved that the Guanhe super large bridge’s parallel chords and flexible arch were closed with high precision,therefore the closure controlling methods put forward in this paper are verified to be reliable,which can provide reference to similar engineering.