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Re: Steel I Beams

From: kevinmurray@sbcglobal.net
Category: Structural
Remote Name: 67.119.90.98
Date: 14 Nov 2005
Time: 10:14 AM

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Question: We are trying to free-span 30 feet with two steel I beams that will support about 13,000 lbs of live load (floor at L360) located from one side to just past mid-span, plus a dead load of about 7,000 over and above the weight of the I beams. The beams are to be spaced roughly 16’ apart (open area between). Can this be done with beams that are less than 14” deep? Flange width is not limited, but the 14” depth is critical.

Builders Websource Answer: Your description is slightly insufficient to compute the minimum steel i-beam size. Specifically, the precise loading diagram would be required showing how the loads are transferred to the beams (and where) and whether there are other point loads, non-uniform loads, or other loads such as wind/snow loads, seismic loads, etc. Furthermore L/360 may be the minimum code requirements for live load floor deflection, however, for a long span, this level of deflection may not "feel" adequate. Many quality construction jobs require very stiff floors, particularly if the floor will have tile, concrete, or other brittle material. It's not uncommon to specify deflections limited to L/480 or even L/1000 for longer spans. If you can fax or mail us a simple loading diagram so we can better see the precise dimensions and how the loads are transferred to the steel i-beams, we can give you a ball-park answer to your question. Please note, however, that specification of structural members must be performed by a structural engineer licensed in your state and any answer we provide will be for illustrative purposes only. Builders Websource also offers BeamChek, which is a cost-effective structural wood and steel i-beam design software application for professionals. Click HERE for more information on BeamChek.

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