A seismic retrofitting design approach for activating dissipative behaviour of timber diaphragms in existing unreinforced masonry buildings

The region of Groningen (NL) has experienced increasing human-induced seismicity caused by gas extraction in the last decades. The local building stock, not designed for seismic loads, consists for more than 50% of unreinforced masonry buildings with timber diaphragms. In this context, a detailed seismic characterization of timber and masonry structural components has taken place, and a retrofitting technique for timber floors activating their energy dissipation has been developed. Besides, specific analytical and numerical modeling strategies for as-built and retrofitted timber floors have been formulated. This work presents a design approach for creating strengthened dissipative timber diaphragms, and maximizing the seismic capacity of existing masonry buildings through this retrofitting method. The results from the performed numerical analyses prove that the proposed design approach for timber floors can increase the energy dissipation capacity of masonry buildings, while improving the box behavior at both damage and near-collapse limit state.