Volume 12, Issue 5 (September 1984)
Comparison of Nailed Joint Test Methods
Six different test configurations were studied to evaluate the effect of test methods on the load-slip behavior of nailed joints. The apparati considered are those used by five researchers in addition to that described in ASTM Method for Testing Mechanical Fasteners in Wood (D 1761). The load-slip parameters evaluated were: first and second cycle secant slip moduli at design load, loads at 0.38- (0.015-) and 2.54-mm (0.100-in.) slip, ultimate load, and slip at ultimate load. These parameters were evaluated for joints nailed with 6d and 8d nails in single shear and interlayer (connector) gaps of zero and 0.51 mm (0.02 in.). Douglas fir lumber and plywood were used as main and side members, respectively. The results indicate that first and second cycle slip moduli are highly sensitive to the test apparatus used. Sensitivity decreases as parameters are taken further along the load-slip record. Beyond 2.54-mm (0.100-in.) slip, no statistically significant differences were found as a result of the methods used. The profound effect of interlayer gap on slip modulus is apparent, while the influence of number of nails used in a specimen is insignificant. Finally, the need for accurate slip measurement and three-point support foundation for test specimens loaded in compression is emphasized.