Fabrication Rules of Thumb - Beam Length 2

[MegaStructures]

Are there rules of thumb for specified lengths of hot-rolled steel beams considering fabrication quality?

There's a conversation in the office whether a W10x45 can be rolled in one 30ft piece, or if it needs to be split and spliced in the field to avoid warping from the mill. My hunch is that this shape would be just fine to be milled at this length, but I am curious if there are certain rules of thumb that other offices follow for this. I do know all members should be limited under 40ft to allow for transportation on the main roadways without special permitting.

Thanks

 

[BridgeSmith]

My hunch would be that whatever special handling considerations would be required to prevent warping would be far less expensive than a bolted field splice, especially if it's not going to a fabrication shop for other additions, i.e. it's a plain beam without any stiffeners, etc.

It may have a bit of camber from the milling process, but I think usually they're just placed with the camber up so that there's less sag when it's loaded.

If the final shape is critical, consider using a welded plate girder.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dhengr]

NetTension:
30’ is no problem for a W10x45, we would have mill ordered those in 60’ length as warehouse stock, and cut them to length. Look in the AISC Manual or ASTM A6 (I think it is) for mill tolerances for steel material. We would normally pick and orient that beam so that any mill tolerances did not hurt you. Allowable camber (any existing camber) would normally be placed upward as we fabed the rest of the member, connections, etc. so that it was counteracted by the deflections when put in place.

 

[dhengr]

NetTension:
I believe, that within reason, over length motorway shipping permits are less difficult to manage (and get), than over width or excess heights, which just can’t be managed easily (or practically) under bridges and the like. Under normal conditions length becomes an issue on lighter beams because they’ll buckle under single point lifting. Fabricators have generally learned to live with mill tolerances, and still provide you with a good/quality finished product. But, you should still read and understand ASTM A6 because it will help you understand how steel products are made and when things that you do, design, detail and otherwise, make the fabricator’s job more difficult. Almost anything you would do with field welding a splice, etc. would likely introduce more problems and cost than dealing with mill tolerances.

 

[BridgeSmith]

Also, that 40' length limit without a permit seems low. 53' long box trailers are fairly common, as are flatbed trailers in the 50'+ range. I'm fairly sure the 60' rebars we regularly specify don't require any permits to get delivered to our jobs, either.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[SlideRuleEra]

Check the catalog of a major AISC member manufacturer of your choice, like Nucor-Yamamato.

Their answer, for W6 through W44, (page 23 of the .pdf above), up to 80'... and manufacturing tolerances (length, camber, sweep, crossectional area, weight and ends out-of-square) are spelled out in the AISC Manual of Steel Construction, as dhengr mentioned.

http://www.SlideRuleEra.net

 

[DrZoidberWoop]

Yes. W10 members can be rolled 30'+ and still fall within ASTM A6 tolerances (AISC Table 1-22 for reference). I'm looking at my company's "Available Inventory" spreadsheet, and we have a lot of light W10's that are 40' long (even 1 60 footer).

 

[MegaStructures]

Thank you all for the helpful and well thought out responses

 

[phamENG]

I absolutely agree with what everyone else has said, but I will give you a word of warning - pay attention to how the erector installs it! I had two projects with small outfits doing the steel (a 4 storefront commercial building and a convenience store) where the erector screwed up. The shopping center had a spandrel girder with about the maximum allowable sweep (curvature out of plane) from the mill, and they installed it with the sweep out of the building. This wasn't caught until joist seats were already welded into place (with inadequate bearing near midspan) and it caused an absolute nightmare when it came to supporting the trusses for canopy out front without telegraphing the shape of the beam into the canopy. On the other, a long window sill was installed camber down, leading to angry phone calls accusing me of under designing the beam.

It's important to understand mill tolerances and erection tolerances, how they should be handled in the field, and how to detail around them. In both cases the mistake was on the other guy, but all the clients remembered were the additional fees to redesign the canopy attachment and support the joists on the one hand and a delay due to a perceived (though disproved) design flaw.