| Earthquake is a natural disaster with extremely destructive power.More than 90% of the casualties and conomic losses from building damage and catastrophic collapse caused by strong earthquakes.As a very effective passive damping(vibration)control device,the viscoelastic damper has the advantages of simple structure,convenient manufacture and low cost.So the viscoelastic damper has good application prospects in practical engineering.Reinforced concrete(RC)frame structures are widely used in various types of buildings.At present,scholars have done more research on the viscoelastic damping technology of RC frame structures and have achieved many valuable results and conclusions.However,there are still some shortcomings on this issue.In particular,the traditional mechanical models of viscoelastic materials/dampers are mostly based on macro-scale phenomenological models,which lack the ability to start from the microscopic scale and link the macroscopic mechanical behavior of viscoelastic materials/dampers.Traditional assessment methods for structural and component damage are usually based on some macroscopic parameters such as displacement,strain,strength,stiffness and energy dissipation.There are few studies on the damage and failure modes of viscoelastic damping RC frame structures from the material scale to the component scale.The seismic response research of viscoelastic damping RC frame structures mostly adopts two methods of shaking table tests and pure numerical simulation calculations.There are few seismic simulation hybrid test methods that can well combine the advantages of shaking table tests and pure numerical simulations.Therefore,it is necessary to conduct further in-depth research on the viscoelastic enhancement and damping technology of RC frame structures.In this paper,a series of researches have been carried out from the dynamic mechanical performance tests of viscoelastic dampers,the mechanical models of viscoelastic dampers,seismic performance and cross-scale damage evolution models of viscoelastic damping RC frame structures,seismic design parameters of viscoelastic damping RC frame structures,and the hybrid tests of viscoelastic damping RC frame structures.The specific research work is listed as follows.(1)A series of dynamic mechanical performance tests of viscoelastic damper independently developed by our research team are carried out in a wider temperature range,a wider frequency range and a wider displacement amplitude range.The focus is on the influence of ambient temperature,excitation frequency and displacement amplitude on the dynamic mechanical performance and energy dissipation capacity of viscoelastic dampers.The results show that the viscoelastic damper has excellent energy dissipation capability and good adaptability to the external environment,and its dynamic mechanical performance and energy dissipation capability produces the strong dependence and obvious coupling effect on temperature,frequency and displacement amplitude.(2)Based on the experimental research of viscoelastic dampers,the micromechanical properties and energy dissipation mechanism of viscoelastic materials are analyzed.The high-order fractional derivative model is employed to comprehensively describe the mechanical properties of the microscopic molecular chain,and the Kraus theory is introduced to consider the influence of filler particles.Combined with the principle of temperaturefrequency equivalence,a high-order fractional derivative micro-macro cross-scale mechanical model is proposed.The results show that the proposed model can comprehensively describe the influence of ambient temperature,excitation frequency,displacement amplitude,microscopic molecular chain structure,and filler particles on the mechanical performance of viscoelastic materials and dampers.(3)Based on the above-mentioned characteristics of viscoelastic dampers,which have good energy dissipation performance and can provide certain rigidity,a structure system strengthened by using viscoelastic damping haunch braces frame(VBF)is proposed.A comparative study on dynamic performance of VBF specimens and ordinary RC frame specimens under wide-band horizontal sinusoidal steady-state excitation is carried out.On this basis,a comparative study of the qualitative and quantitative relationship between material-scale damage development and component-scale performance degradation for the two types of specimens is carried out.A cross-scale damage evolution model of viscoelastic damping structure is established,and then it is simplified and validated.The results show that the addition of haunched viscoelastic damper braces(HVEDB)can greatly improve the seismic performance of RC frame structures.The damage of the beam-column node area can be successfully transferred to the beam area,and it ensures the seismic design requirements of “strong joints and weak components”.The proposed model can comprehensively and accurately describe the damage evolution of the structure on the whole process,and it realizes the cross-scale conversion of damage information from the local material scale to the component scale.(4)For 50 specimens under different working conditions,the effects of important seismic design parameters such as axial load ratio of frame columns,HVEDB setting mode,and shear span ratio of frame columns on the seismic performance of the proposed VBF system are comprehensively studied.Combined with the material-scale damage index proposed above,a qualitative and quantitative comparative study on the material-scale damage evolution of this structural system on the whole process under different seismic design parameters is carried out.The research results reveal the influence rules of axial load ratio,HVEDB setting mode,and shear span ratio on the seismic performance and damage failure mode of the VBF system,and the superiority of this structure system is further verified.(5)To more truly reflect the influence rules of strong-nonlinear viscoelastic dampers on the seismic response control of RC frame structures,a series of hybrid tests of viscoelastic damping RC frame structures under seismic excitation are researched.Firstly,a user-programmable hybrid simulation platform is developed,and the core implementation details of this platform,including the core architecture,hardware system,and software system,are described in detail.Secondly,to better realize the accuracy and stability of the hybrid simulation experiment,a method for solving the equivalent force equilibrium equation for hybrid simulation experiments on viscoelastic damping structures is proposed.Then,the inner loop control and outer loop control(hybrid test loop)of the hybrid simulation platform are tested and verified.Finally,based on the hybrid simulation platform,a series of hybrid tests of viscoelastic damping RC frame structures are carried out under a wide temperature range environment,different seismic intensities,different damper locations,and different seismic wave excitations.The test results truly reveal the influence of temperature,earthquake intensity,damper locations and seismic waves on the seismic response of viscoelastic damping RC frame structures.The main highlights of this paper are listed as follows.(1)A series of dynamic mechanical performance tests on the viscoelastic damper are carried out.On this basis,a high-order fractional derivative micro-macro cross-scale mechanical model that can comprehensively describe the influence of ambient temperature,excitation frequency,displacement amplitude,micro-molecular chain structure and filler particles on the mechanical performance of viscoelastic materials and dampers is proposed.(2)A structure system strengthened by using viscoelastic damping haunch braces frame is proposed,and the seismic performance of this structure system is analyzed comprehensively.On this basis,a cross-scale damage evolution model that can comprehensively and accurately describe the damage evolution of the structure on the whole process is proposed.(3)A user-programmable hybrid simulation test platform is developed.A method for solving the equivalent force equilibrium equation for hybrid simulation experiments on viscoelastic damping structures is proposed.Based on this hybrid simulation platform,a series of hybrid tests of viscoelastic damping RC frame structures are successfully carried out under a wide temperature range environment,different seismic intensities,different damper locations,and different seismic wave excitations. |
PDF Full Text Request