Research Of Vibration Isolation Of The Small Scale Bridge System Based On Smart Bearing

When traditional passive bearings are in the face of earthquakes and other destructive shocks,they can not change their own stiffness to resist destructive and shear deformation,nor can it increase the energy dissipation by adjusting the damping.Stiffness and damping of the new smart bearing based on magnetorheological materials are adjustable,these can enhance the seismic performance of the bridge.It requires a lot of vibration tests to make sure the new smart bearings can be used in the bridge.These tests are expensive and difficult to operate,so the modeling of bridge system is of great significance.Because the simple geometric similarity can not reflect the dynamics of the prototype system,the model construction method derived from similarity theory provides a way to solve this problem.This thesis makes research on vibration isolation performance of bridge used the new smart bearing and builds a small-scale bridge vibration isolation system.Results of simulation and experimental show that the small-scale bridge vibration isolation system has the same dynamic characteristics with the actual prototype system.And then make analysis on the vibration isolation effect of smart bearing,the main contents are as follows:1.The significance of small-scale bridge vibration isolation system based on smart bearing is discussed.The research of bearing isolation vibration,magneto-rheological technology and similarity theory are reviewed.Then,the main research works of this paper are put forward.2.The seismic wave is decomposed into a superposition of the sine wave and the three-span bridge is reduced to an equivalent mechanical system.Take a three-span bridge as a prototype,and make analysis on the vibration isolation performance of the system by MATLAB when it is vibrating near its natural frequency.The results show deck acceleration amplitude decreases by 20%,deck displacement amplitude reduced by 30% compared to traditional passive bearings.The energy consumption of bearing is increased with the shear force and the acceleration transfer rate is significantly reduced near 4 Hz.3.The similar-modeled method of small-scale bridge vibration isolation system and the influence of the kinetic parameters of the model material on the vibration isolation system are discussed.Then makes analysis on the similarity of model and prototype in acceleration,displacement and acceleration transfer rate.The results show that the small-scale system and the prototype system have similar vibration characteristics.4.The small-scale bridge isolation platform is built,and the data acquisition system is composed of acceleration sensor,displacement sensor,signal acquisition module.Then the vibration table which can simulate the earthquake is selected,and the vibration isolation test method is designed.Then makes analysis on the similarity of model and prototype by tests.The results of tests show that the small-scale system and the prototype system have similar vibration characteristics.Then makes analysis on the vibration isolation effect of smart bearing in time domain and frequency domain,The results show smart bearing can ensure the safety of the bridge because the deck acceleration amplitude decreases by 30%,the deck displacement amplitude reduced by 55%.5.Magnetorheological-damper is added to the vibration isolation system,because the damping of smart bearing is not enough.Then makes analysis on the vibration performance of the system under free vibration and forced vibration by simulation.The results show that the vibration isolation performance of the system is improved.Then make experimentally studied on the vibration isolation system with magnetorheological-damper,and The results show deck acceleration amplitude decreases by 20%,deck displacement amplitude reduced by 20% compared to MRE bearings.