Seismic Control Of Metallic-Friction Composite Damper Under Very Rare Earthquakes

Energy dissipation technology dissipates the seismic input energy of the structure,reduces the seismic response of the structure,and improves the seismic performance of the structure by installing energy dissipation devices in the structure.When the structure is suffered from wind load or earthquake load and vibrates,the relative displacement and relative velocity are generated by structural deformation,and the damper is used to reduce the structural response and achieve the expected seismic requirements of the building structure.Commonly,These traditional energy dissipation dampers are of a single type of shock absorbing device,namely only as a kind of energy dissipation mechanism of dissipation of energy,can’t adapt to all levels of the earthquake,such as,according to seismic design in small,metallic damper under strong earthquakes,the damper due to external load is exceeded the limit deformation ability causes damage,not energy consumption;If the friction damper is designed according to large earthquakes,it can only provide stiffness for the structure under the action of frequently occurred earthquake,but can not work and consume energy.In view of the above background,this paper innovatively proposes a new composite damper:Metal-friction Composite Damper（MFCD）,MFCD mainly relies on the hysteretic energy dissipation of metal entering plastic stage under small and medium earthquakes and the Friction and metal cross energy dissipation under large earthquakes to consume most seismic energy,thus reducing the dynamic response of the whole structure.Achieve the purpose of energy dissipation and shock absorption.So that it can achieve the design goal of"multi-line defense,two-stage energy dissipation"and effectively avoid the displacement failure of the damper.MFCD ingeniously combined the advantages of metal damper and friction damper,the two learn from each other,effectively increase the capacity of energy dissipation and earthquake applicable capacity of the damper,and then achieve the"1+1>2"combination effect.In this paper,the damping performance of metal-friction composite damper is studied by methods of theoretical analysis,numerical simulation and experimental study.The main research contents are as（fo1ll）owDse:duction of restoring force model and Mechanism of the MFCD:The design structure and working mechanism of MFCD were introduced,the energy dissipation mode and parameter design of MFCD units were analyzed,and the optimal sliding displacement x_foptwas determined according to the maximum energy dissipation.Based on the mechanical models of metal element and friction element,the restoring force model of MFCD was deduced and analyzed,and the mechanical model expressions of each section curve of MFCD restoring force model were proposed.It provides sufficient theoretical basis for subsequent damper test and seismic performance analysis.（2）Pseudo-static test of the MFCD:Firstly,the pseudo-static test scheme of metal friction composite damper（MFCD）was designed.According to relevant specifications,the specimen design,material test,loading system and device were determined in detail.On this basis,the quasi-static test of friction metal composite damper（MFCD）is carried out to analyze the influence on the performance of the damper,and the hysteresis curves under various working conditions are studied and analyzed.The working mechanism of MFCD with two-stage operation and hierarchical energy dissipation was verified,and the experimental results were basically consistent with the theoretical model.By changing two key parameters of bolt preload and friction coefficient,the energy dissipation mode and hysteresis curve of MFCD were studied under different parameters.The advantages of MFCD compared with traditional damper are verified by the comparison of metal damper,friction damper and friction metal composite damper with the same design parameters.Compared with traditional MD,MFCD has the characteristics of never losing displacement.Compared with traditional FD,MFCD can produce energy dissipation during small and medium shocks.（3）Numerical simulation analysis of MFCD:Based on ABAQUS finite element analysis platform,a three-dimensional solid model of metal friction composite damper was established by selecting appropriate steel constitutive,friction contact and element type,and conducted the comparison of the numerical and experimental results.On this basis,the influence of the steel yield strength,steel thickness,bolt preload,friction coefficient and other variables on the energy dissipation capacity of the composite damper is further studied.（4）The research on the energy seismic design method based on the behaviors of MFCD:A performance-based energy seismic design method for MFCD energy dissipation and shock absorption structures is proposed.The connection unit of SPA2000 is used to simulate MFCD effective damping device,and three natural ground motion records are selected according to the site conditions of the engineering example.The dynamic nonlinear finite element analysis is carried out for the MFCD damping structure without control and installed under the action of moderate,large and extremely rare earthquakes respectively.The analysis results show that,MFCD has good control effect on interlayer displacement Angle,top layer displacement and base shear.