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- To: <seaint(--nospam--at)seaint.org>
- Subject: Re: steel connections/ fabricator
- From: THunt(--nospam--at)absconsulting.com
- Date: Tue, 25 May 2004 07:11:55 -0700
The UBC intent is that the Engineer who designed the structure also design the connections that resist seismic loads. The Engineer of Record (PE or SE) provides the number of bolts, sizes of welds, and thickness of plates then the detailer provides the nitty gritty dimensional details such as actual spacing of bolts, coping cut outs, actual end to end member dimensions, etc. As previously mentioned, most West Coast engineering offices (and other offices around the country I am sure) have a set of typical details that the detailer feeds off of. These typical details generally provide the size/number requirements but leave enough dimensional wiggle room for the detailer to make everything fit. I have had very few calls from fabricators wanting to drastically change the connection details.
As a side comment, I discussed this issue with some "East Coast" engineers once and asked them how do they actually transmit the loads to the fabricator. There were several methods ranging from giving the fabricator a one inch thick STAAD report to all sorts of spreadsheets. The problem was how does the fabricator combine the loads, when and how does he use the 1/3 factor, and if using LRFD which load factors does he use. I found in many cases engineers were giving the fabricator the maximum of each load type (DL, LL, S, W, E) thinking this was conservative. It may be conservative for column compression but certainly not if there is potential uplift.
Thomas Hunt, S.E.
05/24/2004 08:04 AM
Is this meant to read that the SEOR must design the connections, or that the connections must be designed by a SE? You'll probably find little disagreement that the detailer/drafter shouldn't be designing connections without the supervision and seal of a PE. On large steel structures (in my old firm - I don't do much large steel now) we provided only reactions and moments unless the connection performance required a specific detail, in which case we would provide it. I would say 98% of all connections were designed by the Fabricator, and sealed by the Fabricators engineer. (the big F in Fabricator is meant to be the company, Joe's Steel Corp., not a particular draftsman/welder)
Actually, we would usually get requests to modify nearly all of our in-house designed connections. As building designers, rather than full time steel detailers, our connections were usually 50-200% more expensive to fabricate than the "preferred" method, for the same strength and performance connection. That "preferred" method varied by steel house, based on their expertise and shop equipment - as we found out when re-using an "efficient" connection method on a subsequent job, only to find that the new steel house "didn't usually do it that way". The cost in construction administration manpower was not justified for all but the most critical situations.
At 07:16 AM 5/24/2004 -0700, you wrote:
I missed the original post on this thread but in regards to the East Coast versus West Coast detailing issue part of the reason it is rarely done on the West Coast is that it is discouraged by the building code. UBC Section 1633.2.3 reads "Connections that resist design seismic forces shall be designed and detailed on the drawings". The commentary to this section from the SEAOC "Recommended Lateral Force Requirements and Commentary C108.2.2 reads "In some geographical regions, particularly those with low seismicity, a practice has evolved that leaves the design and detailing of connections to the fabricator or constructor (notwithstanding its criticism by the American Society of Civil Engineers). This practice is absolutely prohibited by this provision......".
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