Experimental Investigation of the Repairability of a Cantilever Cross-Laminated Timber Diaphragm

Cross-laminated timber (CLT) has gained considerable interest in recent years as a low-carbon alternative to steel and concrete in construction. While CLT structures are designed to withstand extreme events, such as strong earthquake shaking, without collapsing, the aspect of postevent repairability is not explicitly addressed in current US design codes. This study thoroughly investigated the repairability of a previously tested $6.1\times 6.1\mathrm{m}$ ($20\times 20\mathrm{ft}$) cantilever CLT diaphragm that was damaged from reversed cyclic loading. Inspection and assessment of each of the components and connections indicated that the damage was localized to the connections (glulam-to-CLT screws and CLT-to-CLT surface splines), and the damaged diaphragm was deemed repairable. The repair strategy was intended to restore the capacity of the postrepaired diaphragm to the design strength of the initial undamaged diaphragm by replacing the damaged fasteners and surface splines with new connections. The repaired diaphragm was subsequently retested. The test results showed that the repaired diaphragm displayed slightly higher peak strength and comparable deformation capacity when compared to the initial diaphragm. This research underscores the potential viability of repairing damaged CLT diaphragms for performance restoration. However, further testing that encompasses other diaphragm configurations and varied fastener types may be needed to develop more comprehensive and effective repair strategies.