Researches On Seismic Performance Of Knee Braced Steel Frame With Viscoeiastic Damper

To take into account both the advantages of viscoelastic damper and knee brace,make the structure have two energy dissipating and seismic response reducing defence lines in earthquake,the author propose that set viscoelastic dampers in the knee braced steel frame,which called knee braced steel frame with viscoelastic damper in this paper.Compared with the traditional aseismic system knee braced steel frame with viscoelastic damper are more safety and technically reasonable.Based on the research results at home and abroad,the author sum up the aseismic effect factors of knee brace and presented reasonable design proposals of knee braced steel frame with viscoelastic damper in this paper.The author describe the mechanical properties and the dissipation mechanism of the viscoelastic material in detail,introduce the construction of general viscoelastic dampers and the construction form and characteristics of viscoelastic dampers used in this paper,expound the effect factors of viscoelastic material,present reasonable threshold range of energy dissipation knee brace,introtuce the characteristics of various viscoelastic damper mathematical formulas, present the mathematical formula of general viscoelastic damper and energy dissipation brace used in this paper,analyze the brace stiffness effect to performance parameters of energy dissipation set,present final simplified mathematical formula of viscoelastic damper energy dissipation knee brace when the brace stiffness was far greater than the damper equivalent stiffness. For in-depth study the aseismic performances of knee braced steel frame with viscoelastic damper,three simplified frame buildings,pure frame,eccentrically braced steel frame and knee braced steel frame with viscoelastic damper are eatablished using Ansys,a large-scale finite element analysis software.Dynamic characteristics analysis and dynamic nonlinear time-history analysis under earthquake are carried out,the result indicate that the energy dissipation brace of knee braced steel frame with viscoelastic damper can increase the lateral stiffness of structure and dissipate energy at the beginning of the earthquake which reduce the displacement response and internal forces of the structure greatly,the main framework can be well protected under earthquake,also the energy dissipation device can greatly reduce the seismic response of strucutre in different spectral characteristics of earthquake.Knee braced steel frame with viscoelastic damper has good site adaptability.Lastly,there are several problems studied subsequently brought up based on the researches of this paper.