how do you check the strength of a bolt for construction?

Question

im looking to get a construction supervisers licance in massachuttes ..and one of the questions i have is what is the way to check the strength of a bolt for construction..and im sitting with the code book in front of me wit my face in my hands tryin to figure it out. its not in my calss notes or my practice questiond help thanks Ben (naturally im weeding out the fools that say wack it 4 times wit a hammer so please hav a clue what yur talkin about Thanks

in my class the teacher spoke on torqe and electronic tension test or somthing i swear i jus caught the tail end of the sentance ....? you all seem so close but not quite what im lookin for >>>>i definatly feel like im communication with the right group....or it might be that the elecrtic type is not feasable so the real method turned out to be !...anyone else?...lol

Answer 1

There are markings on the heads of structural bolts that identify the bolt grade.
While of course one could do laboratory tests, I am unaware of any field tests for strength (but there are some tests for proper installation) However, the 1989 ASIC spec. (the only one I have a copy of, no doubt there is a newer version by now) says in section A3.4 "Manufacturers certification shall constitute sufficient evidence of conformity with the standards"
So if the bolt head markings indicate that the bolt is what the engineer specified, and the manufacturer says the bolts meet spec. then the strength is presumably OK

[EDIT] in the "additional information" you mention torque and something about tension, as I said before there are tests for proper installation, which can involve calibrated torque wrenches or tension indicating bolts and perhaps other methods, but that is not really checking the bolt _strength_ (which was your original question)
My copy of the AISC manual is a bit out of date (9th ed. ASD) , but it includes the "Specification for Structural Joints Using ASTM A325 or A490 Bolts" and in section 8 there is information on proper tightening, and section 9 has some information on inspection.

Answer 2

Testing bolt strength can be done by an independant lab that has the proper equipment...usually, it's done by clamping the bolt in a machine that then uses hydraulic force to pull it apart or shear it and records the force exerted in doing so. Most bolt hardware has stamping marks on the head that indicate what strength the manufacturer has produced them to be but bolt failure in some critical locations has prompted some projects to require such sample tests be done before construction begins to assure quality standards are met. Years ago there was a flurry of poor metal and inferior bolt strength from Asian manufacturers that concerned a number of engineering projects.

Answer 3

Bolts when required for construction are ordered in accordance with a material specification that specifies the required bolt strength.

When the bolts are made they are marked on their heads with a code that indicates the bolt strength, usually to an ASTM Specification code.

The bolts are not normally tested at assembly.

See this website for a description of the markings:

http://www.unified-eng.com/scitech/bolt/boltmarks.html