Seismic Retrofitting of RC Buildings Using Cross-Laminated Timber Panels: Insights from the ERIES-STRONG Project

Abstract Timber, with strength-to-weight and modulus-to-strength ratios comparable to steel, is increasingly utilized in seismic retrofitting due to its versatility, sustainability, and rapid installation potential. However, concerns exist regarding its capacity to respond effectively to seismic events, particularly the risk of delayed activation compared to existing structural damage. Timber retrofits high deformability, largely attributed to the ductility of metal connections, enables significant displacements without compromising stability. Nonetheless, challenges arise when timber systems interact with brittle materials, such as in retrofits of reinforced concrete (RC) and masonry buildings, questioning the conventional ultimate limit state. This study examines the application of cross-laminated timber (CLT) panels for retrofitting RC buildings, as part of the Sustainable Timber Retrofit Of reinforced coNcrete buildinGs (STRONG) project conducted at STRULAB, University of Patras, within the ERIES framework. A two-storey RC frame with masonry infill, representative of 1950–1970 Mediterranean construction practice, was retrofitted using a CLT-based technique (RC-TP) and tested under lateral cyclic loading up to ultimate conditions. The intervention prioritized life safety and global stability over damage containment during high-intensity events. This paper outlines the design criteria and experimental results, highlighting the potential of CLT panels to enhance seismic performance while ensuring structural stability.