huangyhg

osha anchor requirements
per osha 1926.755(a)(1), all columns require 4 anchors. however, i still see a lot of smaller columns (ts 4x4x3/16) using only 2 bolts at the base, which seems ok for such a small column. is everyone else using the 4 bolt minimum for all columns sizes?
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columns weighing less than 300 pounds are exempt from this four bolt osha requirment.
i respectfully disagree with c2. the way i interpret osha 1926.755(a)(1), is that all columns require four (4) anchor bolts. i do not see any exceptions where less than four bolts are acceptable. osha 1926.755(a)(2) states:
鈥淓ach column anchor rod (anchor bolt) assembly, including the column-to-base plate weld and the column foundation, shall be designed to resist a minimum eccentric gravity load of 300 pounds (136.2 kg) located 18 inches (.46m) from the extreme outer face of the column in each direction at the top of the column shaft.鈥?br>
that part exclusively deals with the size of the weld to resist overturning moment. it does not allow for the use of 2 anchor bolts if they are 300 pounds or less. four bolts will resist overturning moment due to lateral loads imposed on the column during erection/construction. the challenge i have with the four anchor bolts is physical limitations. i have instances where the four bolts were crowding corners and they had impact on sequence of construction.
if i am mistaken, please let me know. i am always willing to learn.
i hope this helps.
please see the following thread:
less and is axially loaded (a load presses down on the top end), or (2) is not axially loaded, but is laterally restrained by the above
does it actually say 4 bolts, or can a properly arranged set of 3 meet the loading requirement?
trying to work out a corner tube column with offset baseplate. one corner gets no bolt.
what you need to do is put 2 bolts on each leg of a corner base plate. it really defeats the purpose of requiring the (4) bolts.
what was the motivation for the 4 bolt requirement? i believe i read that it had something to do with column failures during construction. can anyone confirm this? what is the structural engineers obligation as far as adhering to osha regulations? we are not the ones on the site doing the work. i think you have to make it possible for the erector to adhere to osha, but it is not our obligation to see that the erector does.
sperlingpe,
i think you are partially correct, the designer is generally not liable for on site safety and we should say so in our contract documents. however, osha does require certain design criteria to be met. for example, the load capacity of a handrail which is specified in the osha regulations is the designer's responsibility, but the installation is not. just as the 4 anchor bolt requirement and the 300 lb eccentric load for a column is the designer's responsibility, but the installation of the column is not.
i guess i want to know what is the background of this particular osha regulation. i agree that required loads/loadings need to be accounted for. this particular case deals more with erection than it does for design of
i envision the reason for the requirement by picturing an ironworker scrambling up a freestanding column; one that is not yet tied in by beams and thereby subject to swaying out of plumb.

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