Timber-Based Seismic Retrofit of a 5-Storey RC Structure Built in 1955

The paper presents a study on the seismic behaviour of a 1955 masonry-infilled reinforced concrete (RC) building subjected to two alternative timber-based interventions to reduce its seismic vulnerability. The first intervention (named RC-TPext) consists in the application of crosslaminated timber (CLT) panels from the outside of the building, while the second (RC-TP) sees the replacement of the outer masonry wythes with CLT panels. Various building configurations were analysed: i) as-built, with the masonry infills included solely as mass; ii) as-built, with the infills modelled as equivalent diagonal struts; iii) retrofitted with the RC-TPext intervention; iv) retrofitted with the RC-TP intervention. Each configuration was analysed by making two alternative hypotheses about the properties of the existing material. The numerical analyses confirmed the importance of considering the masonry infills in the evaluation of the as-built seismic response, and proved the effectiveness of the proposed retrofit interventions. The results showed that the proposed timber-based retrofits can markedly improve the seismic behaviour of existing buildings characterised by poor material properties and construction detailing.