huangyhg

lock washers
during a random inspection i notice a gc had installed lock washers between the nut and hardened washer on a a325 3/4" bolt used to support a steel frame platform.
aisc does not allow the use of this non-astm lock washer right? i know the hardened washer is recommended for this purpose alone but why would a gc install a lock washer?
lock washer not allowed.
aisc requires that a hardened washer be installed on high strength bolts. the washer is to be installed under the turning element of the bolt. if the nut is being turned to achieve bolt tension then the washer is to go under the nut. the same is true if the bolt head is being turned.
the reason is simple, high strength bolts when turning will "chew" up the softer structural steel!
good luck
wirelesstom - the contractor probably assumed that he/she was being helpful and "adding value" to the project. i doubt if there is any more to it than that. perhaps you can explain to him/her why this is not acceptable.
if the original specs were for a 307 which may have spelled out the use of lock washers and the contractor instead installed a325 (or better) because "he had them on hand" or for whatever reason, he must be warned that, even though the original specs were a307, just the act of installing a325 require that they be installed at a 325 specs. some gc's will come 'unhinged' at the thought but, i have had to explain it to a couple of them in years past.
rod
ronfff"> put it in a nutshell, lockwasher not allowed. better use an "anco" locknut.

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