Experimental validation of analytical equations for retrofitting masonry buildings with timber frames and boards

This paper is the second of a series of two, discussing the analytical assessment of the seismic behavior of an innovative timber retrofit for unreinforced masonry structures. The retrofit system consists of timber frames, connected to the masonry piers and to the floor diaphragms, with oriented-strand board sheathing nailed to the frames and to flexible timber diaphragms. The companion paper [1] focused on the conceptual bases of the proposed solution, providing analytical equations for the design of its components, and a step-by-step design procedure for their practical application. In this paper, the proposed formulations are validated against the experimental data coming from in-plane quasi-static shear-compression tests on masonry piers and dynamic shake-table tests on a full-scale building prototype. These tests were performed on nominally-identical specimens in both bare and strengthened configurations, allowing a direct comparison between the experimental and calculated retrofit contribution. In particular, the analytical formulation was applied to reproduce the in-plane response of individual piers, to reproduce the base shear-interstory drift envelope of the building specimens, to assess the out-of-plane strength of walls, and to validate the flexible diaphragm enhancement. Overall, the proposed formulations revealed a good match with the observed retrofit performance and failure mechanisms.