Research On Seismic Mitigation And Energy Dissipation Of Concrete-filled Steel Tube Stiffened Skeleton Arch Bridge Based On Buckling Restrained Braces

Concrete-filled steel tube stiffened skeleton arch bridges are widely used in highway and railway bridges in China,and the span of such bridges usually exceeds 300 m.Its aseismic design is not clearly specified in the current code,so it is necessary to carry out targeted individual research on the actual bridge.As a new type of seismic mitigation device,buckling restrained brace is widely used in the seismic design of building structures,but less in the seismic design of bridge structures.The purpose of this thesis is to study the seismic mitigation effect of buckling restrained brace on the long-span concrete-filled steel tube stiffened skeleton arch bridge under earthquake action and to obtain a reasonable seismic mitigation design scheme.The main research work in the thesis is as follows:1.The seismic research of long-span arch bridges and buckling restrained brace at home and abroad were reviewed.The structure,type,mechanical parameters and mechanical model of buckling restrained brace were summarized.The development of standards and codes of buckling restrained brace was introduced.(Chapter1、2)2.In this thesis,a long-span concrete-filled steel tube stiffened skeleton arch bridge under construction was taken as the engineering background.Three dynamic calculation models included arch rib model,main bridge model and full bridge model were established,and the dynamic characteristics of the three models were compared and studied.The results show that the first vibration modes of the three models are all transverse symmetric bending vibration,which indicates that the transverse stiffness of the bridge is weak,and the transverse seismic design should be strengthened in the seismic design.Half of the first eight order vibration of the whole bridge model is related to the longitudinal vibration of the abutment pier and the columns above the arch.It can be judged that in this type of bridge,the abutment piers and the columns above the arch are weak under the action of earthquake.(Chapter3)3.The transverse seismic mitigation effect of concrete-filled steel tubular stiffened skeleton arch bridges under the buckling restrained brace was studied.The influence of four parameters,including the number of layer,the arrangement form,the yield bearing capacity and the inner core material,on the seismic mitigation effect under the buckling restrained brace was discussed.In the end,a reasonable transverse seismic mitigation scheme was obtained.The results show that the buckling restrained braces adopt three-layer and X type,the yield bearing capacity adopts 8000 kN,and the inner core material adopts LY100 low-yielding steel for the best transverse seismic mitigation effect.(Chapter4)4.The longitudinal seismic mitigation effect of concrete-filled steel tubular stiffened skeleton arch bridges under the buckling restrained brace was studied.The influence of three parameters,including the arrangement angle,the yield bearing capacity and the inner core material,on the seismic mitigation effect under the buckling restrained brace was discussed.In the end,a reasonable longitudinal seismic mitigation scheme was obtained.The results show that the arrangement angle of buckling restrained braces adopts 45°,the yield bearing capacity adopts 8000 kN,and the inner core material adopts LY100 low-yielding steel for the best longitudinal seismic mitigation effect.(Chapter5)...