Experimental Study of Disproportionate Collapse Prevention Mechanisms for Mass-Timber Floor Systems

Abstract

This paper presents and discusses experiments examining the responses of mass-timber floor systems under idealized removal of an interior load-bearing wall. Testing was performed on continuous double-span (2×L) and discontinuous single-span (L) floor assemblies with both conventional (lap-joint and self-tapping screws) and novel (additional internal steel tubes) floor-to-floor panel connection detailing. The continuous floor systems depended solely on the panels’ bending resistance, and brittle failure occurred at a deflection of 6% of L. Improved performance associated with ductile behavior was obtained with the introduction of floor-to-floor connections with maximum deflections of 8% and 12% of L for conventional and novel detailing, respectively. For the floors with conventional connection detailing, failure was observed after compressive arching due to the low axial strength and ductility. The addition of steel tubes enabled catenary action, in which the floor systems maintained high load-carrying capacity while undergoing large deflections. This study demonstrated that adequate connection detailing can ensure structural robustness of mass-timber floors for disproportionate collapse prevention.