Studying Performance of 3 Passive Control Methods to Improve Seismic Response of Moment Steel Frames (Technical Note)

For seismic control of structures, energy dissipation systems are basically used to facilitate repair and seismic retrofit as well as limiting inelastic behavior in specific ductile devices designed accordingly. The main advantage of using passive control is to switch from earthquake resisting structural design to seismically controllable design of structures. In this paper, influence of using three passive control schemes: Visco Elastic Damper (VED), Tuned Mass Damper (TMD) and base isolation on reduction of seismic structural response like displacement, acceleration and base shear is investigated. The properties of a linear visco-elastic material can be determined by applying a periodic excitation and monitoring the response that involves both an amplification and a phase shift. The frequency of a TMD is tuned to a particular structural frequency so that when that frequency gets excited, the damper will resonate out of phase with the structural motion, thus energy is dissipated by the damper inertia force acting on the structure. The act of isolating an object involves providing an interface between the object and its neighbors which minimizes interaction. Therefore, it is logical to isolate the structure at its base and prevent the ground motion from acting on the structure. For this purpose, 6 moment frames of 5 to 30 stories were modeled using nonlinear finite element software. To study numerical behavior of frames in different cases, typical sections were selected for models subjected to the El Centro earthquake for time-history analysis. Based on the results, using base isolation significantly reduced base shear, story drift and acceleration while the other two methods, although convincingly reduced lateral displacements, generally increased the accelerations. Due to lateral stiffness increase, adding VED increased the frame base shear but TMD showed no major drawback.