Design And Research Of Longitudinal Anti-falling Beam Device Of Simple Supported Beam With Lead Core Rubber Bearing

At present,there are relatively few researches on the anti-falling beam measures of seismic isolation Bridges in China.Through the investigation of the earthquake damage in Maduo,Qinghai Province,it is found that the simplysupported beam Bridges using rubber bearing also have the risk of falling beams,and additional anti-falling beam measures are needed.At present,Chinese researchers add the limitation measures already used are more,each has each advantage and disadvantage.In this thesis,a longitudinal anti-falling beam device is designed according to the lead rubber bearing commonly used in the simple supported beam bridge in high intensity area.The component design,mechanical properties,working mechanism,seismic performance and application of the limiting device are systematically studied.Taking the multi-span simply-supported beam bridge with lead core rubber bearing as an example,the anti-falling beam device designed by me is analyzed by using nonlinear dynamic time history analysis method,and the working mechanism,seismic performance and parameter analysis of the anti-falling beam device are discussed.The main research contents and conclusions of this thesis are as follows.(1)Investigate the earthquake damage of falling beams at home and abroad,and analyze and summarize the causes of falling beams.On the basis of falling beam earthquake damage,this thesis makes a comparative study of the current commonly used measures to prevent falling beam,and preliminarily summarizes the advantages and disadvantages of various measures from the aspects of concept design,application range and design method.(2)A typical multi-span simply-supported girder bridge in the western High region is established by using the finite element numerical simulation method.The seismic response law of simply-supported long bridge with or without falling-down beam device is analyzed from the aspects of longitudinal displacement response of main beam,longitudinal displacement of pier bottom,internal force of pier bottom,relative displacement of pier beam and relative displacement of beam beam,and the action mechanism of the falling-down beam device is analyzed in depth.It is concluded that the anti-falling beam device can effectively limit the relative displacement of pier beam.(3)The seismic response of multi-span Bridges is analyzed by studying the number and location of falling-proof beam devices,the compressive stiffness of falling-proof beam,the initial gap of falling-proof beam and other factors.It is concluded that the falling-proof beam device only has a great influence on the pier with the device,but has little influence on the ordinary pier.It is suggested that the compressive stiffness of falling-proof beam device should be selected according to the multiple of the pushing stiffness of pier.The selection range is 0.5～1.2 times,and the initial clearance is65%～80% of the ultimate displacement of the selected support.(4)Based on the application results of the falling beam protection device in the real bridge structure,it is concluded that the advantages of the two seismic systems can be combined by the falling beam protection device to realize the emergence of the isolation mechanism and the ductility mechanism in turn.