Research On Dynamic Performance Of Translational-Rotational Friction Isolation Bearings

The displacement of friction sliding bearing is too large after the earthquake,and the friction pendulum bearing with the reset performance can rise the beam body in the earthquake,which cause additional damage to the bridge easily.Based on the existingspherical bearings,a translational-rotational friction isolation bearing having both horizontal and vertical vibration isolation performance is put forward.Which is combined with wear-resistance property of UHMWPE and damping property of ZA27 alloy to ensure the isolation effect,improve the level of energy consumption and horizontal bearing capacity and decrease excessive displacement.This paper introduces the structure and working principle of the new bearings firstly,the force-displacement expression is obtained under unidirectional loading and cyclic loading,the frictional resistance of the stages is calculated and the restoring force model is established.The static contact analysis is carried out by using ABAQUS,and two kinds of bearings deflection or not are simulated.The influence of UHMW-PE material parameters on static results is studied.The change rules of hysteresis curve,equivalent damping ratio and energy consumption is analyzed when the horizontal slip,bayonet clearance and friction coefficient change respectively.After determining the hysteretic model of bearings,the simple harmonic displacement excitation is applied on the bearings,the effect of parameter variation on dynamic performance is studied.By adjusting the peak value of the measured seismic wave acceleration and applying it to the bearing base,the displacement,energy and acceleration response of the bearing under different seismic fortification intensities were studied.Finally,a bearing-pier finite element model was established to study the weakening effect of the upper measuring point under low frequency harmonic vibration loads,the effect of the thickness of ZA27 alloy and plate material on the results.The conclusions include:(1)The theoretical derivation of the hysteresis curve has high precision,in variable parameter analysis,the maximum error of energy consumption between numerical simulation and theoretical calculation by simplified formula was 13.1%,the maximum error the damping ratio of is 9.02%,the bearing theoretical model simplified formula can be used to study the hysteresis of the bearings,it can meet the requirements of engineering calculations.(2)The friction coefficient of the rotating surface 2 has a greater influence on the equivalent friction resistance of the rotating part,and the influence coefficient is about 2 times of the rotating surface 3.(3)The displacement response of the bearings under the 8 degree Tianjin wave is more than that of the Taft wave and the El wave,and the bearings are more suitable to be used in the fortified area of hard site and the middle hard site.(4)Under 8 seismic fortification intensity,the friction coefficient of the rotating surface has a significant effect on the slide displacement controlled by the bearings,and the maximum displacement amplitude can be reduced by more than 30%of the pure sliding bearing.(5)Under 8 degree seismic fortification intensity,when d0 ranger from 40 mm to 80 mm,the displacement control effect is better.According to the results of displacement and energy response,the k2 is suitable for range 1.5?2.5 and d0 is suitable for 40?60 mm under type 3 seismic waves.(6)With the increase of the excitation frequency,the vertical damping effect of each measuring point is gradually weakened,1?6 Hz vertical vibration excitation frequency in each measuring point can be reduced by 21.39%?67.77%,the vibration level is reduced by 2.09?9.83 dB.The damping rate of 6?14 Hz is 14.63%?33.06%,the vibration level is reduced by 1.37?3.49 dB;the damping rate of 14?20 Hz is 6.42%?25.68%,and the vibration level is reduced by 0.58?2.58 dB;(7)By analyzing the damping effect of different thickness of ZA27 alloy,considering the effect of damping and the cost of using,the 12.5?15 mm is suitable for the design of ZA27 alloy thickness.