Ductility and overstrength of nailed CLT hold-down connections

The structural performance of nailed hold-down connection systems used for cross-laminated timber (CLT) shear walls under monotonic and cyclic loading was experimentally evaluated. Critical connection performance parameters, including strength, stiffness, ductility, and overstrength, were derived from the testing of 68 hold-down connection specimens. The nailed CLT hold-down connections achieved moderate to high ductility when fracture failures of their metal brackets were avoided. The hold-down connection systems with 3 mm thick commercial brackets achieved ductility factors ranged from 2.7 to 4.3, while the hold-down connection systems composed of 10 mm thick steel plates and longer nails achieved larger ductility factors which ranged from 4.7 to 6.3. The overstrength factors of the hold-down systems ranged from 1.45 to 1.62 except the one composed of the 10 mm thick brackets and 100 mm long nails installed at wide spacing. It was also found that the yield strength of the nailed hold-down connections under monotonic loading was similar to that obtained by cyclic loading.