Load-Slip Behavior of Nailed Joints in Seven Amazonian Hardwoods

Two hundred ninety-two nailed joints in seven species of Amazonian hardwoods were tested to evaluate their load-slip (P-Δ) behavior when subjected to lateral loading. The seven species commonly used in Brazilian light-frame construction had a range of specific gravities from 0.36 to 0.85 (based on an oven-dry volume) Four sizes of common wire nails were used to construct joints with main and side members of the same species. From these tests, embedding strength values associated with a 5% offset load were obtained from the experimental (P-Δ) curves and equations derived from the European Yield Theory. The results suggest that the behavior of nailed joints made with tropical hardwoods is similar to that found in temperate zone species. Wood moisture content, in the range studied, did not meaningfully affect joint P-Δ behavior. In addition, embedding strength was influenced by the specific gravity of the connected material. However, no species effect was observable between species of similar specific gravity. Finally, an effect of nail diameter on embedding strength was seen; however, the lack of homogeneity of test materials precluded the accurate prediction of this effect. Since the embedding strength data demonstrated some degree of positive skewness, three commonly used statistical distributions (log-normal, three-parameter Weibull, and Johnson's SB) were evaluated to quantify the variability of this parameter. All three distributions were excellent descriptors of behavior. Therefore any of these mathematical models would be a rational choice for representing embedding strength.