Cyclic Loading Behavior of Nail and Dowel Laminated Timber Diaphragms

Mass timber has seen widespread adoption and increasing interest across North America over the past decade, including in regions of mild to moderate seismicity. A potential manufacturing method to construct mass timber floor diaphragms is by assembling sawn lumber using either nails or wooden dowels into nail-laminated or dowel-laminated timber panels. This paper presents the results of quasi-static monotonic loading capacity testing of several nail-laminated timber (NLT) and dowel-laminated timber (DLT) diaphragm assemblies with different configurations. Three configurations of NLT/DLT diaphragms were tested by varying the nail spacing as well as the diaphragm type, with an additional light-frame wood diaphragm to serve as a benchmark specimen for comparison. All specimens were tested utilizing a slightly modified CUREE protocol. The tests’ results showed that both the NLT and DLT diaphragms have higher capacity and stiffness than a comparable light-frame wood diaphragm, with all diaphragms tested significantly exceeding code-predicted capacity and stiffness. This study represents, to the best of our knowledge, the first systematic testing effort on NLT/DLT diaphragm assemblies under reverse-cyclic loading conditions.