Research On The Seismic Responses And Design Method Of SDOF System With Viscous Dampers

In recent years,FVD has been widely concerned in civil engineering field due to its advantages in mechanical properties.With the development of damping devices,viscous damping systems are expected to be widely used.Based on this,some problems in time history analysis of viscous damping systems were studied in this paper:?1?For the first time,the selection of ground motion intensity index used in time history analysis of SDOF system with FVD was studiedFirst of all,SAP2000 was used to establish the calculation model of SDOF system with FVD,and 22 far-field seismic waves were selected as the seismic input for time history analysis.Then,the correlation between the seismic response of the SDOF system with FVD and 18 kinds of seismic itensity indexes was calculated and analyzed,a theoretical formula for calculating the correlation between the comprehensive seismic response of a structure and the intensity index of ground motion is presented.Research showed that:in 0.1s⁰.6,0.6s²s and 2s⁶s three cycle period,correlations between the earthquake responses and the ground motion peak acceleration PGA,the peak speed PGV,the first period velocity Sv are higher,so in these three cycles respectively choose PGA,PGV,Sv as main indexs for ground motion selection.?2?The influence of structural parameters on the damping effects of FVD was studiedTaking the SDOF system with FVD with T=0.5s and T=2s as the research object,13seismic waves were selected as the ground motions input to analyze the influence of intensity reduction coefficient?and post-yield stiffness ratio b on the seismic response reduction rate of the structure,the energy dissipation ratio of FVD?E_d?and the additional damping ratio??eq?.Research showed that when intensity reduction coefficient is constant,the increase of post-yield stiffness ratio is beneficial to improve the acceleration response reduction rate?a_d?,velocity response reduction rate?v_d?,base shear reduction rate?F_d?and the energy dissipation ratio of FVD?Ed?.The reduction rate of displacement response?ud?reaches its maximum value when the post-yield stiffness ratiob=0.The?eq increases with the decrease of the post-yield stiffness ratio.When the post-yield stiffness ratio is constant,the vd,ud and Fd decrease first and then increase with the increase of intensity reduction coefficient.The ad and the Ed decrease with the increase of intensity reduction coefficien.the increase of intensity reduction coefficien is beneficial to increase the?_eq.?3?The influence of ground motion characteristics on the additional damping ratio was systematically analyzedA total of 98 ground motions in the near and far fields were selected to calculate the additional damping ratio of the SDOF system with FVD.The variation rules of the additional damping ratio with important duration,the peak acceleration and the spectral characteristics?PGV/PGA,PGV/PGA?of ground motion were analyzed.The research showed that the important duration has a relatively weak influence on the additional damping ratio;The additional damping ratio decreases with the increase of the peak vibration acceleration everywhere,and when the peak vibration acceleration increases from 70gal to200gal and 200gal to 400gal,the additional damping ratio decreases by 53.6%and39.4%;The additional damping ratio decreases with the increase of PGV/PGA and PGV/PGA;A fitting relation between the additional damping ratio and PGV/PGA and PGD/PGA is proposed.?4?A simplified design method for viscous damping structures is proposedBased on the existing design method of system with viscous dampers,the calculation method of additional damping ratio which can consider the characteristics of ground motion is proposed.the numerical examples show that the proposed method can avoid the repeated trial calculation of the design parameters of viscous damper,and the reliability of the calculation formula presented in chapter 5 is verified.