Vulnerability reduction of structures under dynamic loadings

In the present work a suitable retrofitting strategy is presented for reducing the vulnerability of under-designed structures subject to dynamic loadings. After the recent seismic events in Italy the seismic codes have been modified and the seismic risk associated to a large part of the territory has been substantially increased. Many structures build in the past with respect to obsolete standards no longer satisfy the current technical standards for the seismic codes. In the present work a retrofitting strategy for under-designed structures is investigated by the adoption of steel braces realized in series with innovative buckling restrained axial dampers in the nonlinear modeling of the dissipative behavior of structures under dynamic actions. The adopted retrofitting approach shows to be useful for the mitigation of the seismic risk of under-designed structures by providing a suitable increment of the safety degree of under-designed structures. A pushover analysis is performed in order to determine the capacity curve of the considered under-designed structure and the safety factors are evaluated for the structure before retrofitting and after the innovative retrofitting. The reported analysis shows that the investigated innovative retrofitting strategy can be usefully applied for an effective reduction of the seismic vulnerability of under-designed structures by suitably increasing the safety factors of the investigated structures subject to dynamic loadings.