Fundamental Research of an Evaluation Method of Splitting Failure in Timber II.

Effect of specimen shape on splitting strength when loaded parallel to grain

Abstract

The mechanism of splitting of timber loaded parallel to grain is not clear and it is difficult to evaluate the splitting strength. In this research, splitting tests on Japanese cedar and Douglas fir were conducted to clarify splitting strength. A monotonic tensile force was applied to a drift-pinned joint with steel side plates and splitting failure originated from the pin hole. In order to evaluate the splitting strength, specimens with various parameters, i.e., diameter of drift pin, end margin, edge margin and thickness were used. All parameters affected the splitting strength, but particularly, end margin and thickness also affected the failure mode. As the end margin lengthened, the failure mode was transferred from shear to splitting. On the other hand, as thickness increased, the drift pin bent more at splitting. This bending of the drift pin caused a lag of bearing stress to timber, and the failure mode was transferred from full width splitting to partial width splitting. The splitting strength under various conditions could be evaluated by consideration of the difference in failure modes.