Seismic Performance Research Of Lateral Anti-drop Beam Limiter For Medium And Small Span Girder Bridges

Several domestic and foreign bridge earthquake damage investigation reports have shown that the phenomenon of large displacement or even falling beams in the upper structure of the bridge is very prominent,and the block,as an important component to limit the lateral displacement of the bridge and prevent the disaster of falling beams,was not caused enough attention in the design and construction.Most of the existing studies focus on the common concrete blocks widely used in bridge engineering,and often do not consider the possibility of repair or replacement of the blocks after earthquake damage.According to the design idea that the block becomes the "fuse" of the bridge structure,the block should play the function of deforming and destroying the main structure before the earthquake occurs,consuming the seismic energy,and protecting the main structure of the bridge from damage.Based on this,this paper proposes a lateral anti-falling beam limiting device suitable for medium and small span girder bridges.It has the characteristics of simple manufacture,convenient installation and remarkable energy consumption effect.The bridge has strong engineering significance and application prospects.In this paper,a full-scale anti-falling beam limiting device is designed according to the concept of structural seismic block,and verified by experiments.The test specimens are made of low-yield steel,and four kinds of anti-drop beam devices with different structural sizes are made.Through experimental research and numerical simulation,the mechanical properties of the anti-falling beam limiting device in the quasi-static loading test were analyzed.Then,the anti-drop beam device was applied to typical small and medium-span girder bridges,and the seismic response mechanism and function of the anti-drop beam device were studied by comparing the different seismic responses of the bridge under the installation of ordinary concrete blocks and anti-drop beam limit devices.The main work and achievements of this paper are as follows:(1)The causes of typical beam falling earthquake accidents at home and abroad are analyzed,the constituent elements of beam falling prevention system are studied,and the specification requirements of beam falling prevention system in various countries are analyzed.(2)Through the quasi-static test of anti-drop beam devices with different struct ural sizes,the energy consumption law of the anti-drop beam device is analyzed,a nd the parameters such as the thickness of the web plate of the replacement block,the height of the replacement block,and the installation position of the replacement block are studied.The bearing capacity of the device,the influence of deformation and energy dissipation capacity,verify the replaceability of the replacement block.(3)The finite element model of the anti-drop beam device was established,and the nonlinear analysis was carried out with the parameters of the web thickness,web height and installation position of the device replacement block.The results of the finite element model were compared with the test results,and the medium and small spans were determined.The specific size requirements of the lateral anti-falling beam limit device of the girder bridge.(4)A typical small and medium-span girder bridge is selected,and the anti-drop beam device is applied to the bridge.The seismic response of the ordinary concrete block and the anti-drop beam device is compared by time history analysis method,and the effect of the anti-drop beam device on the bridge is studied.The impact of the seismic performance of the structure.