IMPACT OF RETROFIT OF RC FRAMES BY CLT PANELS AND FRICTION DAMPERS

In Italy, as well as in other earthquake-prone countries, most buildings have been erected with-out considering the effects of seismic excitation or according to obsolete seismic design provi-sions. Furthermore, they also suffer from significant structural deficiencies because of the low mechanical characteristics or the natural decay of the materials. The seismic vulnerability of the existing building stock is a serious economic and social concern and the need for retrofit-ting or rebuilding grows as time progresses. In this framework, this study investigates a newly developed retrofit technique for buildings with RC framed structure. The intervention is realized by means of Cross-Laminated Timber (CLT) panels placed over the exterior walls and connected to the RC structure by friction dampers. The CLT panels provide the existing structure with addi-tional lateral stiffness and strength. The role of the friction dampers is twofold. On one hand they cap the internal forces of CLT panels, thus controlling the reaction forces transmitted to the exist-ing structure and avoiding the failure of CLT panels themselves. On the other, friction dampers dissipate part of the input earthquake energy. The effect of these multiple features could reduce the storey drifts demanded by the earthquake to values compatible with the structure capacity. This paper aims at sounding the impact of the proposed retrofit solution on the response of the RC framed structure to be upgraded. To this end, a one storey RC frame representative of existing RC framed structures designed considering only gravity loads is upgraded by a CLT panel and friction dampers of usual size. The impact of the retrofit intervention is investigated in terms of the achieved increase of stiffness, strength and energy dissipation capacity. The bare RC frame and the frame equipped with CLT panel and friction dampers are modelled in OpenSEES environment. Hence, the nonlinear responses of the two frames are assessed by mon-otonic and cyclic pushover analyses and the comparison between the results obtained for the bare and the upgraded frame quantifies the expected impact of the proposed retrofit intervention.