Seismic Performance Of Beam Bridges Supported By Nylon Fabric Reinforced Rubber Bearings

Plate rubber bearings is widely used in small and medium-sized span bridges because of its advantages of high bearing capacity,strong deformation capacity and excellent seismic performance.However,this kind of bearings has higher costs,heavier weight because of the built-in sandwich steel plate.In order to improve its deficiency,domestic and foreign scholars choose fiber material instead of steel plate as the reinforcement layer of bearings,and carry out a series of theoretical,experimental and numerical simulation researches.Based on the existing research,nylon fabric with light weight,good elasticity and low price is used as the strengthening layer in this paper.Nine nylon fabric reinforced rubber bearings with different design parameters,such as fabric layer number and rubber plate thickness,are designed and manufactured.Based on experiment and numerical simulation,the mechanical property of nylon fabric reinforced rubber bearings and the influence of the above design parameters on its performance are studied.The feasibility of using this kind of bearing in the seismic resistance of small and medium span girder bridge is discussed.The main research content and results of this paper are as follows:(1)In the light of the earthquake characteristics of China and the shortages of plate rubber bearings,the research background and significance of this paper were clarified.The research status and development of fiber-reinforced rubber bearings at home and abroad were reviewed.And the research progress of mechanical properties of fiber-reinforced rubber bearings was summarized from the following three aspects,namely the theoretical derivation,experimental and numerical simulation research,and engineering application.(2)In order to investigate the main factors affecting the mechanical properties of nylon fabric reinforced rubber bearings,9 bearings with different fabric layers and rubber plate thicknesses were designed and processed,and the vertical compression and horizontal compression shear tests were carried out on them.The results show that the mechanical properties of the bearings are stable,and no visible damage occurs under the compressive stress of 10 MPa.The vertical compression stiffness of the bearings decreases slightly with the increase of fabric layers.Under 5MPa compressive stress,the shear hysteresis curve of the bearings is smooth and full,and the working performance of the bearings is still good when the maximum shear strain reaches 300%.With the increase of shear strain,the bearings is first curled and then completely rolled.Therefore,the horizontal shear stiffness decreases first and then increases.And the horizontal shear stiffness decreases slightly with the increase of nylon fabric layers.The horizontal equivalent damping ratio of each bearings is between 8% and 14%,and it has strong energy dissipation capacity.(3)The finite element model of nylon fabric reinforced rubber bearing was established based on software ANSYS,and the reliability of the numerical simulation was verified by comparing with the experimental results.The stress changes of nylon fabric layer and rubber layer in the bearing under compression and compression-shear conditions were investigated,and the influence of design parameter on the stress of the bearing was studied.The results show that the numerical simulation results were basically consistent with the experimental results,and the errors were all within a reasonable range.With the gradual increase of compressive stress,the stress of fabric layer inside the bearings increases gradually,and the influence of design parameter is more obvious.Under the compressive stress of 5MPa,with the gradual increase of shear strain,the internal stress distribution of rubber layer and nylon layer is different.The shear stress in the XZ direction of the curling and rolling part of the bearings increases from 0 after 200% shear strain,and the side of the bearings is involved in shear,which gives a supplementary explanation to the test results.(4)Based on software Midas Civil,a three-span continuous beam bridge model with nylon fabric reinforced rubber bearing and basin bearing was established respectively.The mechanical parameters of 9 nylon fabric reinforced rubber bearings in the bridge model were determined based on the test and numerical simulation results of the front bearings seat.The seismic response of the bridge using nylon fabric reinforced rubber bearing for seismic isolation and basin bearing was compared,and the feasibility of the former used for seismic isolation of small and medium span girder Bridges was explored.The results show that,compared with the aseismic structure under earthquake,the longitudinal acceleration velocity,pier bottom shear force,pier bottom bending moment and pier top displacement of the isolated structure are reduced in different amplitude,which has a good isolation effect.And the appropriate increase of the nylon fabric layer of the bearings is helpful to increase the seismic isolation ability of the structure.