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RE: ASTM A325 Bolt using DTI will the Section 7.1 Tension Califra tor test still be needed?[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: ASTM A325 Bolt using DTI will the Section 7.1 Tension Califra tor test still be needed?
- From: "Carter, Charlie" <carter(--nospam--at)aiscmail.com>
- Date: Sun, 2 Dec 2001 07:22:33 -0600
> Reading the November issue Modern Steel
> Construction's Peter Birkemoe's "Structural Bolting Issues."
> I would like to know is "ASTM A325 Bolt Section 7.1 Tension
> Calibrator test" needed when the project uses DTIs for Slip
> Critical joint, class-A slip resistance?
The preinstallation verification outlined in Section 7 of the 2000 RCSC Specification (free download at http://www.boltcouncil.org/) is required as indicated in Section 8.2 whenever bolted joints are indicatedin the contract documents as requiring pretension. That included pretensioned joints and slip-critical joints. The specific requirements for preinstallation verification when the DTI pretensioning method is chosen are given in Section 8.2.4.
Keep in mind that the preinstallation verification required serves many purposes as indicated in the commentary to Section 7, including confirming that the individually manufactured components of the bolt assembly work together, that the bolting crew understands what is to be done and can properly install the bolt assemblies, and, in the DTI method, that the DTIs to be used in the work are performing properly.
> Is it to naive to say the factored-load is for
> LRFD design and service-load is for ASD?
I don't think it is naive. I think it is correct, unless I am misunderstanding your question.
AISC's LRFD Specification is configured assuming you will use the LRFD load factors and load combinations in ASCE 7 Section 2.4.1 for strength design. This is often called the factored load. AISC's ASD Specification is configured assuming you will use ASD load factors and load combinations in ASCE 7 Section 2.4.2 for strength design. This is often called the service load.
Purists will disagree with me, but I have come to accept that both LRFD and ASD really use factored loads for strength design. LRFD's load factors are generally greater than 1 for dead load and the load that is taken in the combination at its maximum lifetime value, but less than 1 for other loads considered in the combination at their arbitrary point in time value. ASD's load factors are generally 1 for dead load and the the load at maximum lifetime value and less than 1 for loads at their arbitrary point in time value. But we do still call LRFD loads "factored" and ASD loads "service" to distinguish between them.
A potential confusion creeps in when you shift thought to serviceability. Design for serviceability is largely uncodified, identical whether you use LRFD or ASD, and generally based upon service-load combinations other than those in ASCE 7. There are several AISC design guides that address serviceability and provide recommendations for appropriate load combinations.
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