A DAMPER-SPRING DEVICE FOR SEISMIC ENERGY DISSIPATION IN BUILDINGS

A damper-spring energy dissipation device connected in series with a cable that is extended throughout the entire structure by an array of pulleys is proposed, which is experimentally tested and validated on a reduced-scale five-story shear building. A series of seismic tests conducted on a shake table show that the proposed system concentrates the inter-story drifts experienced throughout the height of the structure in the proposed damper-spring; therefore, a unique spring-damper system can reduce the seismic response significantly, by increasing the damping ratios of all the structural modes. Different dynamic response quantities are mitigated, including the inter-story drifts, which decrease by about 70% compared to those experienced by the structure without the proposed dissipation system. It is also shown that the proposed scheme provides an energy dissipation capacity comparable to that offered by placing one damper on every floor, confirming the efficiency of this novel device. The system exhibits a significant nonlinear response evidenced by the variations of the natural frequencies and damping ratios of the building during the seismic tests. In particular, the time-variant natural frequencies were identified by using the Short-Time Transfer Function method. Finally, a novel approach is presented and validated that allows determining the time-variant damping ratios and mode shapes of the building by adjusting the model-predicted response with measured absolute acceleration time histories during seismic tests.