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Poll Question: % UDL 1
- Thread starter FoxSE14
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I also obtained 48.6 kips. Others in our office also obtained 48.6 kips.
Brad - close, I am designing some connections and annoyed, not with EOR, but with our fabricator client. On the first pass, their new detailer has taken it upon themselves to program his detailing software to make a generic first pass based on 0.6*TUL/2 i.e.: the capacities of the connections he has designed are sometimes as low as 48.6/2 = 24.3 kips. Obviously a problem, as I assume the EOR (who will ultimately approve our connection designs) is looking for the capacity to be 48.6k, at a minimum.
The fabricator we work for is accusing us of over-designing. We are about to accuse the detailer of unsafe design. Just looking for consensus.
(yes, yes, actual reactions at each connection is preferred...already barked up that tree. We've worked with this client before, the detailer change seems to be the catalyst here.)
Brad - close, I am designing some connections and annoyed, not with EOR, but with our fabricator client. On the first pass, their new detailer has taken it upon themselves to program his detailing software to make a generic first pass based on 0.6*TUL/2 i.e.: the capacities of the connections he has designed are sometimes as low as 48.6/2 = 24.3 kips. Obviously a problem, as I assume the EOR (who will ultimately approve our connection designs) is looking for the capacity to be 48.6k, at a minimum.
The fabricator we work for is accusing us of over-designing. We are about to accuse the detailer of unsafe design. Just looking for consensus.
(yes, yes, actual reactions at each connection is preferred...already barked up that tree. We've worked with this client before, the detailer change seems to be the catalyst here.)
As someone not familiar with US codes, who rarely does building design and does steel design even less, it looks like a pretty straightforward table lookup and multiply by 0.6 = 48.6 kips.
Doug Jenkins
Interactive Design Services
Doug Jenkins
Interactive Design Services
retired13 said:
That's another question, and as stated could be taken to be ambiguous.
The OP asks for 60% of the total LRFD UDL for a specified beam 20 ft long, which appears to be straightforward.
Doug Jenkins
Interactive Design Services
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Well, here's an interesting development. The help file for a known piece of connection software actually gives the following (which aligns with detailer's approach):
So...if I follow that approach, I need to input "120%" into their UDL input box if I want to obtain 48.6 kip capacity [ 1.20*1620/(2*20) = 48.6k ] ..seems very counter-intuitive to me.
I've sent an inquiry to their support staff.
"The UDL % is a way to have the link calculate the design shear forces on a beam in your model. This is done considering the AISC 14th edition manual Tables 3-6, 3-7, 3-8 and 3-9 for wide flanges and channels. These tables have a Wc/Ωb for ASD and a φWc for LRFD and units of kip-ft. Using the length, L, and the UDL % input the shear force calculation is as follows:
VASD = (UDL %) * ( Wc/Ωb) / 2L
VLRFD = (UDL %) * (φWc) / 2L"
VASD = (UDL %) * ( Wc/Ωb) / 2L
VLRFD = (UDL %) * (φWc) / 2L"
So...if I follow that approach, I need to input "120%" into their UDL input box if I want to obtain 48.6 kip capacity [ 1.20*1620/(2*20) = 48.6k ] ..seems very counter-intuitive to me.
I've sent an inquiry to their support staff.
FoxSE14 - again as a non-USA, non-building, non-steel person, that seems fairly intuitive to me. If you want the connection to take 60% of the total maximum design load, that's 120% of the maximum section end shear load.
Designing connections to have a higher capacity than the beam section also seems reasonable to me.
Doug Jenkins
Interactive Design Services
Designing connections to have a higher capacity than the beam section also seems reasonable to me.
Doug Jenkins
Interactive Design Services
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48.6 kips
Detailer is being blindly clever and not understanding the concept. There is definitely a nuanced misunderstanding in their judgement. But assuming a bolted connection for the W16, you'll have 4 bolts in the web anyway and the capacity will be reliant on the trickle down effect from that.
The wording of the desired load is not exactly clear. We use to short-form it to "one-half UDL" but only within our office. Anytime it would go on drawings it would be "one-half of the total uniform load that will result in the full bending capacity of the section." So just switch the "one-half" to "sixty percent."
Detailer is being blindly clever and not understanding the concept. There is definitely a nuanced misunderstanding in their judgement. But assuming a bolted connection for the W16, you'll have 4 bolts in the web anyway and the capacity will be reliant on the trickle down effect from that.
The wording of the desired load is not exactly clear. We use to short-form it to "one-half UDL" but only within our office. Anytime it would go on drawings it would be "one-half of the total uniform load that will result in the full bending capacity of the section." So just switch the "one-half" to "sixty percent."
(off topic - when scanning or photographing pages, placing black paper behind the target page will eliminate print-through from the reverse of the target page and the face of the next. This is because most light that makes it through the page is then absorbed and, since the ink on the reverse side of the page is already doing that, that printing will not stand out. Instead only the light reflected from the front of the target page will be recorded.
That's it.
Design safely.)
That's it.
Design safely.)
FoxSE14 - I only just saw your post from 22:16, which explains some of the later comments.
Whatever the ambiguity of the stated requirement, it should be obvious to the detailer that having a generic requirement for connections that only allows 60% of the maximum design load on the beam does not make any sense; so I agree with your position.
Doug Jenkins
Interactive Design Services
Whatever the ambiguity of the stated requirement, it should be obvious to the detailer that having a generic requirement for connections that only allows 60% of the maximum design load on the beam does not make any sense; so I agree with your position.
Doug Jenkins
Interactive Design Services
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