Mechanical Properties And Parameter Analysis Of Variable Friction Dampers

Friction dampers are widely used in practical construction projects because of their simple structure,high energy dissipation capacity,and independence from load frequency.However,traditional friction dampers only have a single slip friction,and it is difficult to determine the value of the slip friction under the action of random earthquakes.To solve this problem,variable friction dampers have come into being,and there are a variety of variable friction dampers in practical engineering applications.Because there is no systematic research method or unified design specification for variable friction dampers,it is necessary to analyse the basic parameters of variable friction dampers.In this paper,a flat plate variable friction damper based on the "spring-slope" mechanism is selected as the object of study,its mechanical properties are analysed,and its parameters are compared and analysed to provide a reference for the subsequent in-depth analysis of variable friction dampers and the determination of the parameters of variable friction dampers in actual engineering.The main research process and results are as follows:1.Derive the restoring force equation based on the geometric model of the spring-slope panel type variable friction damper and the energy dissipation principle,obtain its restoring force model and write its principal structure relationship program.The program was verified by using ABAQUS to build its finite element solid model,and the motion state of the friction plate at the time node of going up and down the slope was analysed by the ABAQUS solid model.2.According to its restoring force model,the model of a single degree of freedom energy dissipation and damping structure system with a spring-slope panel type variable friction damper is established,and the energy dissipation equation of the single degree of freedom system under resonant excitation and seismic excitation is derived by combining the dynamic balance equation and energy analysis method.The main parameters affecting the energy dissipation capacity of the variable friction damper are determined according to the obtained equations: friction coefficient and prestress,slope section length share,slope section angle,and disc spring stiffness.3.The spring-slope panel-type variable friction damper intrinsic structure program is brought into the calculation software of a single-degree-of-freedom system based on Newmark’s implicit algorithm,and the elastic-plastic time analysis of the single-degree-of-freedom structural system with a spring-slope panel-type variable friction damper attached under resonant excitation is performed.With the determination of the sliding friction in the plane section,the changes in the structural displacement response,energy response,damper output,and energy dissipation ratio when each parameter is changed are compared and analysed.The results show that the plane section sliding friction force is constant.(1)For the variable friction damper,the hysteresis cycle energy consumption with the friction coefficient increases and then decreases,corresponding to the single mass point system in the structure of the displacement showing the trend of increasing and then decreasing.The extreme value of the point can be based on the plane section and slope section restoring force formula combined with other parameters to solve.The increase in other parameters leads to an increase in the hysteretic energy consumption of the damper.(2)Increasing the slope ratio of the variable friction damper can effectively reduce the displacement amplitude of the structure and improve the energy consumption ratio of the damper,and the length of the plane section should be slightly less than the yield displacement of the structure so that the variable friction damper in the structure before yielding the second start.(3)The increase in the slope angle of the variable friction damper can effectively reduce the displacement amplitude of the structure and increase the energy consumption ratio of the damper but also increase the acceleration amplitude of the structure.(4)The variable friction damper disc spring stiffness is basically linearly negatively related to the structural displacement amplitude and linearly positively related to the damper energy dissipation ratio.(5)According to the rules of comprehensive comparison of the effect of all parameter changes on structural motion,it is found that the change in slope ratio and disc spring stiffness has a greater effect on the displacement amplitude and energy dissipation ratio of the structure,so when the energy dissipation capacity of the variable friction damper is insufficient,the priority is to consider increasing the slope ratio and disc spring stiffness within a reasonable range.4.The design of variable friction damper parameters according to the analysis results of the single degree of freedom system was carried out for a practical engineering case for seismic design analysis.The time analysis of the spring-slope panel type variable friction damper damping structure and uncontrolled structure under the action of rare earthquakes was carried out by using SAP2000 finite element analysis software,and the results showed that the variable friction damper was stable in the second start under the action of rare earthquakes,the energy dissipation effect reached approximately 30%.