Once characteristic values are determined for each treatment group, these are multiplied by a set of constant reduction factors t o get the base design value. Hence, if the treatment affects the characteristic value and ultimately the design value, then the effect can be related to differences in the mean values, or differences in variation, or both.
For the base design values, we refer to ASTM D 1990-91 (4) for the calculation of E and [F.sub.b], and to ASTM D 245-98 (3) for calculation of [F.sub.v].
The base design values for bending and shear strength properties were reduced by 8.1 and 14.0 percent, respectively, although the allowable stiffness was unaffected.
* The base design values of visually graded timbers are quite close to the design values that result from the small, clear method of properties assignment.
* The base design values derived from testing small, clear specimens sampled from used utility poles matched the published values within 10 percent.
This pooling was done to enable conclusions to be drawn about log processing, to compare these test results to published data, and to provide guidance on possible base design values.
The data from Table 1 also provides an opportunity to calculate base design values for working stress design for the tapered and uniform ponderosa pine groupings that each include butt and tip logs.
The publication also features base design values
for the major western species, adjustment tables, span information, standard sizes, grade classifications, and lumber properties.