A Steel Exoskeleton for Regularization of the Seismic Response in Elevation of Existing RC Framed Structures

Despite the high seismicity that characterizes many areas of the world, structures currently in use are not necessarily able to sustain seismic forces and need to be upgraded to prevent economic and human losses. Hence, this paper proposes the addition of an external 3D steel exoskeleton, named e-EXOS, to existing RC buildings as a technique to mitigate their vertical irregularities and improve the seismic response of the RC frame structures. The effectiveness of the e-EXOS system is tested on a case study RC framed building, designed without seismic provisions. Two sizes of the e-EXOS truss are considered, to investigate if and how much this affects the structural response. The seismic response of the RC frame, with and without e-EXOS, is determined by incremental nonlinear dynamic analysis and the performance is assessed in terms of mean annual frequency of exceedance of the SD and NC limit states.