Built Up Section 2

[SKIAK]

I've been designing a built up section with a channel welded to the top of a wide flange shape to help take some lateral load. I was directed to use the ASD 9th to find allowable stresses and compare that to the elastic section modulus (I was happy to see the same procedure being used in this thread: thread507-181562). The question I have is, is this the best way to do this? I saw Table 1-19 in AISC 13th ed but I couldn't find any kind of design methodology behind it and I've been hard-pressed to find anything other than section properties in text books.

 

[kslee1000]

I think the only concern is the channel-beam connection, which could cost a lot. What are the loads on the beam? Is there anything that you can provide tie-backs? Have you explored using shapes with stronger weak axix properties?

 

[SKIAK]

The beam is for a movable overhead crane so there would be no way to brace it midspan. 36'-0" unbraced length, ASD worst case in combination is 146 ft-kips vertical and 30 ft-kips lateral. I started looking at standard sections that would be able to carry this but I was directed to use the configuration I mentioned above.

 

[ChipB]

Here ya go:

http://www.aisc.org/Content/Navigat...chnical_Resources/Steel_Tools/Steel_Tools.htm

you want "Crane Beam v1.1"

 

[kslee1000]

ChipB: Excellent link.

 

[SKIAK]

Thanks, thats a heck of a lot better than the spreadsheet I made based on the same design guide 7.

 

[FLCraneBuilder]

146 kips veritical and 30 kips lateral might put you in the realm of fabricated plate girders or plate box girders. On several occasions when I've estimated heavily loaded crane runway beams, plate box girders came out a bit more economical than W40's with C18 cap channels. I have not looked in to fabricated single web plate girders, but this might be of interst.
The crane builder can most likely provide pricing of plate box girders for you.

 

[FLCraneBuilder]

One more note:

Crane beam v1.1 is a great tool.

I wish every A&E firm would use it when preparing dwgs for a project. All to often, The A&E firm calls out a crane runway beam 2 or 3 times the size that is needed. The problem is worst with WWTP facility designers. Thats our tax $$ being wasted.

Moreover, when we bid the job, we ask ourselves, should we bid the smaller beam that we know will work (and take the risk that the A&E will not accept our submitted size) or bid what is specified by the A&E (and lose the job to the guys how took the risk)

Best solution: Call out the runways beams to be sized and provided by crane builder - and have the beam provider submit calcs at submittal stage of project.