Seismic Performance of a Hybrid Timber–Aluminium Exoskeleton for Retrofitting RC Buildings: Experimental Results from the ERIES-RESUME Project

This paper presents the outcomes of an extensive experimental investigation on the seismic performance of an innovative exoskeleton retrofitting system, developed as part of the ERIES-RESUME project. The proposed system integrates laminated timber and aluminium components to enhance the structural resilience of existing reinforced concrete (RC) buildings, while also offering the potential for thermal upgrading. Two identical 1:3 scale RC models, representing typical non-ductile structures, were tested on a shaking table at the IZIIS Laboratory of the Institute of Earthquake Engineering and Engineering Seismology in Skopje. The first model, initially unstrengthened, was subjected to seismic loads until significant structural and infill-wall damage was reached. Following appropriate repairs, the exoskeleton was applied, and the model was retested. The second model was equipped with an exoskeleton from the outset. Test results demonstrate significant improvements in seismic performance, including increased stiffness, reduced interstory drifts, reduced acceleration amplification, and reduced infill wall damage. The study confirms the feasibility and effectiveness of the proposed exoskeleton system as a practical solution for retrofitting vulnerable reinforced concrete buildings.