Practical considerations of dowel bearing strength and annular ring/fastener orientation
1995
Winistorfer, S.G.
The orientation of the fastener with respect to annular growth rings can affect the strength of laterally loaded wood connections. Connection properties are dependent on localized dowel bearing strength, which in turn is dependent on the specific gravity of the earlywood and latewood that constitute the annular rings. In the study reported here, dowel bearing strength was determined for matched specimens of three softwood species (southern pine, Douglas-fir/larch, and spruce-pine-fir) using a 0.131-inch-(3.33-mm-) diameter nail. Tests were conducted with the nail oriented radially and tangentially with respect to the annular rings. Specific gravity, percentage of latewood, and number of rings per inch were also determined for each specimen. Results illustrated that although the difference between radially and tangentially loaded dowel bearing strength can be significant, this difference is of no practical consequence. The combination of fastener size (in contact with many growth rings) and the relatively infrequent occurrence of very coarse- and flat-grained lumber resulted in nearly equal values of dowel bearing strength in the radial and tangential directions. Little correlation was found between dowel bearing strength and percentage of latewood or number of rings per inch.
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