huangyhg

lumber grades for analysis
according to breyer ("design of wood structures," 2nd ed., page 126 - an indespensible textbook) "...[t]he combined effect of the adjustments [allowable stresses developed based on astm d245 and d2555, et al] is to provide and average factor of safety on the order of 2.5. [re.: values in the nds.]"
lumber for houses is a good question. austrian spruce is really nice... a good resource is the southern pine council's web site:
most codes require that primary members (top/bottom chords in trusses, or rafters/joists) be no. 2 or better. secondary
a real lumber yard should have no. 2 lumber no problem. no. 3 lumber is typically used for non-load bearing partition walls. like daveviking said, beware of home depot lumber. even if it says kiln dried, it's probably been sitting in the lumber yard for some time to absorb that moisture back. i've pulled lumber of the stack and have seen standing water on the boards below. almost as if they bundled the wood in a torrential downpour.

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借用达朗贝尔的名言：前进吧，你会得到信心!
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