In-plane assessment of existing timber diaphragms in URM buildings via quasi-static and dynamic in-situ tests

Mechanical and dynamic in-plane properties of timber diaphragms are known to be key parameters when determining both the local and global seismic response of unreinforced masonry (URM) buildings. However, few data pertaining to experimental campaigns on performance of existing timber diaphragms are available in the literature. In the work presented here, the outcomes of a field testing campaign conducted on full-scale 100 year old timber diaphragms are presented. Two specimens, being 5.6 x 9.6 m2 and 4.7 x 9.6 m2, were obtained from a 17.0 x 9.6 m2 existing floor and were subjected to a series of cyclic and snap back tests in the direction orthogonal to the timber joists. Adhesive anchors were installed prior to testing due to the deficiencies of the original anchoring system to transfer shear forces. In order to reproduce the inertial load distribution, an ad hoc loading system was developed by means of wire ropes and steel pulleys. Following testing of the diaphragms in the as-built condition, the effect of different refurbishment techniques was investigated. From the results, it seems that even simple and cost effective solutions such as re-nailing of the flooring and the addition of thin plywood overlays are sufficient to achieve a significant increase in the equivalent shear stiffness.