THE EFFECT OF VISCOELASTIC DAMPER ON REDUCING SEISMIC RESPONSES OF STEEL FRAME STRUCTURES

When subjected to an earthquake motion, a structure should absorb and dissipate lots of energy in different ways, allowing the structural members to enter the inelastic range enabling them to absorb the energy by their deformations. As structural members enter the inelastic range, permanent deformations occur, and to continue utilization of structure, those members which are too deformed or cannot be utilized anymore should be strengthened or replaced with new members, an operation which is difficult and costly. Therefore, the dampers installed in the structure, through energy absorption induced by earthquake, prevent other parts of the structure to enter inelastic range; as a result, following an earthquake, different parts of the structure can be either still utilized or fixed and replaced, if necessary, by checking the dampers.
According to the aforementioned things, this study aims to examine the structures to which damper is added as a retrofitting method. For this purpose, by selecting a number of intermediate steel moment frames, seismic vulnerability of these frames in the near- and farfield earthquakes was examined and such parameters as damage to frames and stories, relative story displacement, base shear and roof displacement were examined. In this study, viscoelastic dampers are used in order to reduce drift and structural damage. The results after dampers installation in the middle span of frames were compared with/without using damper, then it was concluded that viscoelastic dampers play an important role in absorbing energy and reducing damage in buildings. Moreover, drift and base shear as well as roof displacement decrease to a great extent. Comparing near- and far-field earthquakes, it was observed that the intensity of near-field earthquakes was higher causing devastating effects in buildings; installation of dampers, however, highly reduces these damages. Furthermore, the effect of dampers on taller buildings was found to be more, and greater reduction was seen in the examined parameters.