Structural performance of CLT wall-to-foundation connection system in the presence of decay

The structural performance of the cross laminated timber (CLT) wall-to-foundation connection system was evaluated after 12 weeks of exposure in a moisture-laden environment. Three-ply CLT panels were manufactured from southern pine lumber into three treatment groups: dry control, wet control, and fungus-exposed. The CLT panels were mounted with hold-downs using two nail lengths (50 mm and 60 mm) and two nailing patterns (centered and enclosed). Wet control and fungus-exposed specimens were periodically wetted for 12 weeks. Fungus-exposed specimens were inoculated with the brown-rot fungus Postia placenta. The hold-down connection specimens were subjected to monotonic and cyclic loads. The higher moisture decreased the load-carrying capacity but increased the initial stiffness. Fungal decay reduced strength, but this was not consistent across samples, presumably because decay levels also varied. The centered nailing pattern reduced ductility but increased energy dissipation, particularly in the fungus-exposed group, due to the tighter nail spacing and their relatively distant position from the hold-down perimeter where fungal decay was inoculated. The wood was crushed significantly at the nail-wood interface in the wet control group, with minimal hold-down distortion and fewer nail head shear-offs compared to the dry control group. Tension cracks developed along the hold-down perimeter of the fungus-exposed specimens at varying intensities, in addition to severe wood crushing at the nail-wood interface, which eventually led to a combination of shear and tension failure of the middle wood laminate in a few specimens. • Cross-laminated timber hold-down brackets were tested after wet and fungal exposure. • Wetting decreased the connection strength while increasing stiffness and ductility. • Decay lowered strength, stiffness, and ductility, causing brittle wood failure. • Longer nails and centered nailing pattern improved energy dissipation.