AISC requirement for fully tensioned bolts

[MrStohler]

Section J1-12 of the AISC specification requires the use of fully-tensioned high strength bolts for specific connections.

What is the basis for this requirement? It appears to have originally noted in the 6th edition of the Manual of Steel Construction and been carried through each subsequent edition.

Please advise if there is any research or analysis to substantiate the need to fully tension these bolts.

Thanks

 

[ishvaaag]

Normally it must correspond to the much diminished impact under dynamic loadings, for the stress range must be the same. I know for sure bolts of poles for direction boards in roads either crack themselves or the pressed plate. Not having any run to move with a final blow but just elastic deformation must give longer fatigue life.

 

[MrStohler]

I am trying to gain an understanding of why certain connections in structures over 125 feet high are required to use fully tensioned bolts. Note that AISC requires only fully tensioned bolts, not slip critical connections, is the fatigue performance the same when the faying surfaces might not have comparable friction properties. The AISC commentaries do not address why this requirement is in the code. Why at 125 ft tall structures? What phenomenon occurs in taller structures to make this requirement appropriate?

 

[ishvaaag]

As you see from my reasoning above the important thing is to prevent impact by eliminating free run and loosening. Respect how tall structures are being required such measure, I can only again point to them be more prone (as a building) to suffer gust impact factor...in fact I have heard the shrieks and felt themovements of slender steel building frames here where I live under precisely wind gust impacts.

One past ACI president said that in revisions if the elaborating parties knew not why something was in the code better leave the thing in, for it was placed in the past in the code to prevent some problems known to occur. To me, more impact than fatigue.

 

[MrStohler]

If the potential movement that might occur in the snug tight condition leads to a problem of impact, why does AISC specifically note column splices and girder/beam to column connections? It does not mention wind at all, with respect to other connections it only says "Connections for supports of running machinery or other live loads that produce impact or reversal of stress”. If wind were the rational for this requirement, all wind bracing would require fully tensioned bolts. AISC Connections Manual provides several wind brace design examples using A325-N bolts and makes no note of this requirement (the column splice section does). It is reasonable to conclude that this code requirement is based on more than wind reversal. Please let me know if there is any research to back-up this code requirement. It has been in the code since the 6th edition (first use of high strength bolts). Why is it there?

 

[ajh1]

Have you reviewed the specification and commentary that RCSC puts out to identify the history on this specific requirement? With the latest edition, the use of snug tight vs. fully tensioned bolts has been increased. A copy of these is downloadable from AISC's web site.

 

[ishvaaag]

Colleagues coming here have asked technical question to AISC and the institution has answered clearly and soon, I suggest you do the same, for I am not privy to the history nor fundamentals of the specification.

Then, I was referring to wind as one main source of dynamic solicitation...all dynamic ones concurr in the ability to help at least to loosen the bolts, then produce unaccounted for or unwanted solicitations.

It is natural that the less stringent snug tight-...-fully tensioned-slip critical bolting be used, for economy so demands. There are variegate criteria in other codes other thing that AISC demand respect bolts for even same structures, and even wider must be the range of engineering judgements about.

I frankly doubt that nor AISC nor anyone can prove that for any of the solutions something occurs at 125 ft tall buildings that can not occur in a 100 ft tall building, I meaning here that of course such clause is to me a conventional one aiming to deliver proper -in the thought of the code elaborators- safety standard to the over 125 ft tall structures.

 

[Taro]

Try contacting AISC's Steel Solutions Center at

http://www.aisc.org/faq_search.asp?...ct=TECHNICAL+QUESTIONS+ABOUT+STRUCTURAL+STEEL