Experimental characterization of basic connection properties of Hinoki and Sugi

Abstract

Hinoki (Chamaecyparis obtusa) and Sugi (Cryptomeria japonica) are two promising softwood species gaining attention beyond their traditional use in Japanese residential construction. Following the establishment of design values through in-grade testing and their inclusion in the American Wood Council (AWC) National Design Specification (NDS) Supplement, further evaluation of their connection performance is essential to increase the information about the two species of wood and support broader adoption, particularly in the U.S. construction market. This study characterized the connection performance of these species through a series of standardized tests: withdrawal resistance, lateral resistance, and dowel bearing strength. The objectives were to characterize the yield behavior, withdrawal capacity, and bearing strength of fasteners embedded in the species, and to evaluate the relevance of the predictive equations provided in the NDS for wood construction within the context of the experimental findings. The experimental results demonstrated species-specific differences in withdrawal and lateral resistance performance, with both species exhibiting consistent failure modes in agreement with NDS yield mode predictions, primarily modes IIIs and IV. Dowel bearing strength showed a similar trend to withdrawal behavior, with the species generally exhibiting higher bearing strength values that those predicted by current design equations. While the results were conservative, they indicate that designers can safely employ the current equations for connections in both Hinoki and Sugi. These findings contribute essential connection performance data to support the structural application of Hinoki and Sugi in mainstream construction.