A new viscoelastic damper for seismic protection of steel building frame

Abstract

Viscoelastic dampers (VEDs) are widely used to protect structures against earthquake. Conventional VEDs are generally installed within a diagonal brace configuration which provides a stiff structural system and reduces their effectiveness. In addition, the aforementioned configuration is not suitable for retrofitting purpose and violates architectural requirements. In this study, a new type of viscoelastic damper is proposed in order to improve the seismic performance of steel structures and to overcome the drawbacks of the conventional VEDs. In order to evaluate the performance of the proposed VED, dynamic responses of a 3-story scaled down steel frame equipped with the proposed VED were obtained experimentally and numerically under harmonic excitations. In this stage, ABAQUS software was used to establish a detailed finite element analysis. The results obtained were compared with a frame equipped with the conventional VED as well as a moment resisting frame and braced frames. The effects of the size of viscoelastic layer on its dynamic characteristics were also investigated. In addition, a nonlinear time history analysis of a 10-story full scale steel frame was performed using SAP2000 software to demonstrate the effectiveness of the proposed VED for tall buildings. The results of this study showed that the frames equipped with dampers performed better than the braced frames in terms of reduction in the maximum displacement, acceleration and base shear responses of the 3-story moment resisting frame. Compared to the conventional VED, the proposed VED was more effective in reducing displacements, while it was slightly less effective in reduction of accelerations and base shears. It was also found that smaller thickness of the viscoelastic layer decreased displacement responses, however, it increased acceleration and base shear responses. The larger cross-section area of the viscoelastic layer resulted in smaller displacement responses, but larger acceleration and base shear responses. Thus, analysis of the 10-story frame showed that the effectiveness of VEDs for reducing maximum displacement and acceleration responses were strongly dependent on the characteristics of earthquake records. The proposed VED was more effective in reducing responses of the lower floors. Based on the results obtained, the maximum base shear response of the frame equipped with the conventional VED was smaller than the frame equipped with the proposed VED and larger than the bare frame regardless of the characteristics of earthquake records. The results showed that the viscoelastic dampers have more advantage in preventing the formation of plastic hinges in the frames even under severe earthquake. In addition, compared to the conventional VED, the proposed VED resulted in less damage to the structural members due to less plastic hinge formation. Therefore, the implementation of the proposed VED can overcome the deficiency of the VED in seismic protection of structures.