DEVELOPMENT OF DESIGN TOOLS FOR PLYWOOD-BASED SEISMIC RETROFITTING OF EXISTING TIMBER FLOORS

Reversible retrofitting techniques for protecting architectural heritage against seismic events have found increasing application in existing or historical buildings in the last years. In this framework, the use of wood-based strengthening solutions for both timber and masonry structures has shown promising results, as proved by several recent research studies, highlighting benefits such as reversibility, compatibility, lightness, sustainability, and effectiveness of these techniques. With specific reference to existing timber floors, the superposition of a plywood panels overlay fastened to the sheathing has proved to be an excellent method to improve the seismic response of such structural components. One of the main benefits of this intervention is related to the combination of a great improvement of in-plane strength and stiffness of the diaphragms, with a considerable increase in their hysteretic energy dissipation. In other words, the method does not only improve the capacity of the floors, but also contributes to a reduction in seismic demand, because of the damping effect induced by the yielding of the numerous fasteners. In order to facilitate the design and use of this reversible, efficient and sustainable retrofitting method in practice, this work first presents the derivation of nomograms, based on previously formulated analytical models. The graphs can be adopted by professional engineers as useful tool for a preliminary structural analysis of timber diaphragms strengthened with plywood panels, enabling a more in-depth understanding of the key design parameters and resisting mechanisms. In addition to that, the implementation of a calculation tool is presented, enabling structural engineers to visualize the expected in-plane force-displacement response and energy dissipation of the retrofitted diaphragms. This work can contribute to the promotion of timber-based techniques in the combined structural, seismic, and conservation upgrading of existing buildings belonging to the architectural heritage of seismic-prone countries.