Analysis On Earthquake Mitigation Of Frames With Hysteretic Dampers Made Of Low Yield Point Steel

The earthquake mitigation of frames with hysteretic dampers made of low yield pointsteel is not only related to the number, stiffness, strength, deformation ability of dampers butalso to the stiffness, bearing capacity and other factors of main structures. The paper tries toestablish the optimum arrangement method of hysteretic dampers by discussing the earthquakemitigation of frames with hysteretic dampers influenced by the strength ratio of the dampersystem and stiffness ratio between the damper system and the main structure.Firstly, the paper has a discussion on the principle of earthquake mitigation and introducesthe time history seismic analysis briefly. It particularly discusses the numerical integration thatis the central difference method, hysteretic models that are bilinear model and skeleton shiftmodel of members in the structure and structural computation module adopted in the elastic-plasticity time history seismic analysis program.The elastic-plasticity time history seismic analysis on the single-degree-of-freedom offrames with hysteretic dampers is done, which proves it has validity that the formula of theoptimum strength ratio of the damper system derived from the definition of equivalentdamping ratio. The numerical analysis results indicate that the dampers mitigate seismic actionmost effectively when the strength ratio of the damper system is in the vicinity of the optimumstrength ratio and the formula of the optimum strength ratio of the damper system can beproved by skeleton shift model applied in the damper system.The multi-degree-of-freedom elastic-plasticity time history seismic analysis program forframes with hysteretic dampers is compiled, in which the skeleton shift model for the dampersystem is adopted and which is proved by compared with the results analyzed by ANSYS.Taking the strength ratio of the damper system as parameter, the elastic-plasticity time historyseismic analyses are taken for a set of 9-floors-3 spans frames with hysteretic dampers. Theresults indicate the validity of the formula of the optimum strength ratio of the damper systemapplied in the multi-degree-of-freedom system and the same conclusion that the dampersmitigate seismic action most effectively when the strength ratio of the damper system is in thevicinity of the optimum strength ratio. It can reduce the earthquake response and the damage tothe main structure by attaching hysteretic dampers in it reasonably.