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nds - "tabulated" design loads
national design specification for wood construction; section 11; dowel-type fasteners:
nds 11.2.1 lag screws states: ..."tabulated nominal design values, w, shall be multiplied by all applicable adjustment factors (see table 10.3.1) to obtain 'allowable' design values, w'.
although it states "allowable", and i have initiated these factored tabulated values as such, (with situational safety factors applied) does anybody else apply additional safety factors to these?
the same question applies for all nds dowel-type fastener tables. (not just lag screws)
part - ii
what about other fasteners such as buildex tek screws? the performance data tables list the values as "ultimate". though it is common practice to apply a 4:1 safety factor to such fasteners as expansion anchors, what safety factors do you apply to tek screws?
thank you!
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no additional adjustments for "factor of safety" other than those shown in table 10.3.1 are required. the loads shown in the tables are not ultimate loads.
the n.d.s. equations used to calculate bolt values have safety factors built in. as ctcray indicate no additional adjustments are required. i specialize in glulam and heavy timber design, and always use the adjustment factors in table 10.31. based on over ten years of experience in the wood industry, i have total confidence that designs which comply with the n.d.s. produce safe reliable structures.
the bigger problem i encounter, is people who do not appply the required reduction factors in special design cases. for example connections subjected to high moisture and temperature conditions, or connections made in unseasoned lumber.
also people seem to forget about the group action factor a lot. when ever i see a connection with more than four bolts in a row, the first thing i look at is the group action factor.
in practice what is more important, is how the connection is detailed.

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