SEISMIC RESPONSE OF MULTISTOREYED STEEL FRAME WITH VISCOUS FLUID –SCISSOR JACK DAMPERS

The placing of fluid dampers to a structure does not significantly alter its natural period, but it increases damping from about 2 to 5% (internal damping) to between 20% and 40%, and sometimes even more (Haskell and lee 2007). It is found that external damping beyond 30% results in small decrease in responses, and such increases lead to usage of more dampers (Hanson and soong, 2001). The use of fluid dampers results in reduction of storey shear forces. Due to the viscous nature, fluid dampers reduce drifts and thus column bending moments, while introducing additional column axial forces which are out-of phase with the bending moments (Constantinou MC and Symmans MD 1992). In order to study the response of the structure (internal forces) as a function of time for a specific ground motion, the accelerograms of the design earthquake or having several representative accelerograms of big earthquakes are used. These types of accelerograms with respect to time can be given as input in software and responses of the structures can be found out. The accelerograms are applied to the structure as shown in Fig. 1.