Research On Seismic Performance Of Offshore Isolated Bridges Based On Friction Pendulum Bearing Degradation And Multistage Buffer Limit

The completion and opening of the hong kong-zhuhai-macao bridge is a milestone for China to become a bridge power as a bridge power.Considering that China is a country with frequent earthquakes and the offshore environment is complex,how to ensure the safety and service performance of offshore bridge structures under the action of sudden large earthquakes is an important scientific problem we are facing at present.At present,the most effective seismic method is to reduce the damage to the structure by using seismic isolation technology.By setting isolation layer between the superstructure and the pier,the natural vibration period of the bridge is prolonged and the seismic energy input is reduced.However,when the isolated bridge is subjected to a larger earthquake than expected or a near fault earthquake,the displacement of its isolation support will exceed the limit,resulting in beam falling,collision and even collapse of the isolated bridge.Therefore,in the face of extremely rare earthquake or near fault earthquake,how to effectively limit the displacement of isolation layer on the basis of ensuring the safety of bridge and isolation support is the key problem in the field of bridge isolation technology.This paper mainly carried out the following research:1、Design and theoretical formula derivation of Rotational Mass Friction Damper:In limit the research status,existing isolation Damper response amplifier technologydevelopment trend and based on the advantages and disadvantages of using the ball screw is commonly used in mechanical field put forward a new type of spinning quality Friction Damper(Rotational Mass Friction Damper,hereinafter referred to as RMFD).The basic structure and working principle of RMFD were explained,the theoretical formula of its restoring force was deduced,the restoring force model of RMFD was established,and the pseudo-static test of RMFD was carried out.2、Seismic response analysis of RMFD-SDOF system:Established the RMFD motion equation of single degree of freedom shock absorption system,through the analysis of the MATLAB program to RMFD earthquake under the action of single degree of freedom shock absorption system of the vibration control effect analysis,in view of the equivalent friction,equivalent inertia force parameters are analyzed,and through the establishment of the energy equation of motion for RMFD energy consumption analysis,from the Angle of energy,explains the main energy dissipation mechanism of the RMFD;The finite element software SAP2000 was used to simulate the RMFD model,and the simulation method was verified by comparing the calculation results with MATLAB program.3、Seismic response analysis of offshore isolated Bridges with RMFD limits :SAP2000 was used to establish the nonlinear finite element model of isolated Bridges.RMFD was arranged in the isolation layer of Bridges as the energy dissipation limit device to analyze the seismic response of isolated Bridges under rare and extremely rare earthquakes,and the limit effect of RMFD under different control parameters was discussed.4、Aiming at the problem of displacement overrun of isolation layer under the action of extremely rare earthquakes,a multi-level buffer limit is proposed:Aiming at the problem of displacement overrun of isolation layer under the action of extremely rare earthquakes,a multi-level buffer limit is proposed: RMFD is used as the first-level buffer limit device,and the cable is used as the second-level buffer limit device;Considering two limit schemes,the seismic responses of isolated Bridges with two layout schemes are analyzed.5、Seismic response analysis of offshore isolated Bridges considering bearing degradation and multistage buffer limit:Considering the complicated Marine environment on bridge offshore friction pendulum bearing corrosion effect,using the friction pendulum bearing dry-wet cycle corrosion test of bearing friction coefficient variation law,and in severe and very rarely met under earthquake action,the consideration of friction pendulum bearing isolation bridge seismic performance analysis of performance degradation,and the friction pendulum bearing performance degradation and multi-stage buffering isolation bridge seismic performance analysis of limit.