hole locations wood joists

huangyhg

hole locations wood joists
some building codes show locations for holes in wood
floor joists at different locations. one code showed holes only to be located within middle third of span, others showed only within outer thirds of span and some do not even show locations. both 2" clear from top and bottom and d/3 for dia. which would be the best location
within engineering standards.
the hole should be sized and placed depending on the controlling capacity of the wood member.  it is assumed that the   
from a structural stand point, it depends what stresses are critical for your case.  wood is particularly weak in horz. shear, which for a uniform load will be max near the ends (d dist from support).  longer spans will be critical for flexure, generally toward the center.  wood is also weaker in tendion than compression so cutouts in the tension zone are a bit worse.  but the thing really to watch is splitting or cutting notches that may produce spliting along the grain.  the  national desing spec. (nds 2001) gives guidelines of how to avoid putting notches in the wrong places (nds 4.4.3)
peter von buelow
univ. of mich. - tcaup