| Continuous beam arch bridge is a composite bridge of continuous beam bridge and arch bridge.It combines the advantages of both.It has the characteristics of large span and good integrity,and plays an important role in the bridge traffic line in China.In recent years,the frequency of use on railways and highways has gradually increased,but there are few studies on the seismic response analysis of continuous beam arch bridges and the selection of parameters of seismic isolation bearings.At present,most of the research on the mechanical parameters of seismic isolation bearings adopts the control variable method,ignoring the interaction between the parameters,so that the results are not accurate enough.Therefore,the orthogonal test method is used to study the parameter values of lead rubber bearings,and the main factors and secondary factors affecting the damping effect of bridge structures are explored.Therefore,this paper takes a(90 + 180 + 90)m continuous beam arch bridge as the research object,and uses SAP2000 finite element software to analyze the dynamic characteristics of the bridge structure,seismic response and seismic isolation bearing parameters.The main research contents are as follows :(1)Through extensive research on domestic and foreign literature,this paper briefly describes the research status and background of continuous beam arch bridge and seismic isolation bearing,and introduces the common bridge types and seismic damage forms of continuous beam arch bridge in detail,and summarizes the commonly used analysis method principle of seismic response and various types of seismic isolation device and its working principle.(2)The engineering overview of continuous beam arch bridge is introduced and a threedimensional model is established.The dynamic characteristics of the structure are analyzed by multiple Ritz vector method,and the dynamic characteristics are explored by changing the arrangement of transverse braces,increasing the height of piers and installing lead rubber bearings.The results show that the basic period of the bridge structure is low,the structural vibration mode is dense,the lateral stiffness is low,and the seismic capacity is weak.Changing the arrangement of transverse braces has the least influence on the natural vibration period.Increasing the height of piers and adding seismic isolation bearings can significantly increase the natural vibration period.(3)According to the site conditions,three seismic waves that meet the requirements of the code are selected for input.The response spectrum and time history analysis are used to study the structural internal force response of continuous beam arch bridge under different input direction combinations,and the seismic response law is obtained.The results show that because 2 # pier is a fixed pier and 3 # pier is a longitudinal movable pier,2 # pier bears most of the longitudinal internal force and deformation,forming an asymmetric distribution of displacement and internal force.The maximum internal force response of the superstructure occurs at the arch foot of the 2 # pier top,the lower part is at the bottom of the 2 # pier,and the maximum displacement response is at the top of the arch rib.Different seismic waves in time history analysis produce different internal force results,but the response law is consistent,indicating that the seismic response of the structure is closely related to the selection of seismic waves.(4)According to the seismic response results of continuous beam arch bridge,lead rubber bearing is selected for seismic isolation design.Based on orthogonal test,different parameter combinations of bearing size,lead core diameter,hardening rate and bearing height are studied,and the optimal bearing parameters are obtained.The results show that the seismic response results do not change monotonously with each factor,and the influence of each factor on the seismic response results is different.The optimal combination calculated by the weight matrix is A1B3C3D3,that is,the bearing size is 1200 mm × 1200 mm,the lead core diameter is 200 mm,the hardening rate is 0.2,and the bearing height is400 mm.The hardening rate is the main factor affecting the damping effect of the lead rubber bearing;the lead rubber bearing set according to the optimal combination can significantly reduce the seismic response value of the key parts of the bridge,make the internal force distribution of the structure more uniform,give full play to the bearing capacity of each component,and achieve the optimal damping effect.Figure [91] table [34] reference [76]... |
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