huangyhg

sill plate anchor requirement
have a basic question regarding wood sill plates for which i can't seem to track down an exact source. according to nds table 8.5.3 the minimum edge distance for a bolt loaded perpendicular to grain is 4d for loaded edge and 1.5d for unloaded edge. for a wall subjected to wind pressures (positive and negative directions), this 4d requirement technically prevents the use of 1/2" diameter bolts in a 2x4 sill plate, since half of 3.5 inches is less than 4d distance. of course, 1/2" and even 5/8" bolts are commonly used as anchor bolts. can anyone help clear up the apparent conflict?
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i can't help clear up the question. but i am investing this question on my own, because of construction tolerances. it seems as though inspectors allow 1/2" to 3/4" of plate overhang without consulting the engineer or design professional. this puts me in a position where i have to consider the edge distance to be as low as 1" (considering 1 3/4" edge distance requirement for a drilled and epoxied anchor in conscrete).
anyway, if you've gotten further feedback, i'd love to hear it.
i don't have my code open right now, but i believe that you can have reduced distances with reduced values. we do not let our architects use 2x4 walls on the exterior for this reason (and we are in a 70 mph region), but they usually work for interior walls and partitions with the reduced interior wind load.
depending on your jurisdiction (building code), ibc 2000, section 2308.6 or ubc 97, section 1806.6, both have similar requirements with a minimum 1/2" anchor bolt spaced 6' o.c., no edge distance requirement (loaded or unloaded) except ends (max. 12" and min. 7d). i looked all through my 2001 nds and could not find the 4d reference to loaded edge and 1.5d to unloaded edge for sill plate bolts.
erv,
i thought the 4d and 1.5d refered to all bolts in wood.
what i do in this situation is assume that the bolt is whatever diameter meets the 4d edge distance requirement (and no, edge distance cannot be reduced). therefore, for a 2x4 sill plate, assume the bolt is 3/8" diameter, even if 1/2" or 5/8" is used. but be careful with this -- don't let a contractor install an expansion bolt so close to a concrete edge that it will spall the concrete.
daveatkins
akastud,
the nds requirement of 4d and 1.5d is for bolting two members, main and side
erv,
it appears i am just out of date, i have the 97 nds and it specifically says that edge distance, end distance and spacing shall apply to bolts installed with concrete or steel as the "main or side
section 8.5.4 nds gives full value for 4d and minimum 1/2 full value for 2d and interpolate your actual. 1/2" in 1-3/4 edged distance = 3.5d or 75% full value.
for tall walls, or high thrust due to wind or other pressure, it can be a creative excercise to design the connection. sill bolting may not provide enough in many cases.
alohabob,
section 8.5.4 refers to end distance, not edge distance.
daveatkins
the values that i refer to are perpedicular to grain loading edge distance. i think the length of the plate provides the orientation for end distance typically.

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