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Re: Openings in concrete beams

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How deep are your beams for a 32' span? Standard beams for US parking structures are often much deeper than actually needed. Australia and Asia tend to use different beam shapes that provide much shallower beams!

At 05:57 AM 8/12/2007, you wrote:
Has anyone seen this in practice or done concrete beam design with openings before?
We are working on a new underground concrete parking structure with limited height and overhead clearance restrictions. The footprint is large, like 600 feet in the short direction so we need ventilation. We have 32 foot long and 63 foot long beams and 32 foot long girders. The longer beams are governed by bending, not shear at mid-span. I have preliminary beams designed to just fit the height. The architect is asking us if we can put an elongated hole in the beams and girders for ducting and pipes. These of course would be at the mid-span and not exceeding 1/3 the depth. I would prefer to use a round hole but they are asking for elongated holes. I can't find anything in text books or literature for designing an opening in concrete beams.
Has anyone done this type of beam design method before? Has anyone seen concrete structures designed with openings in the beams? Does anyone have a book or reference I can look for to find examples or methodology?
Seems like it would be more efficient to increase the floor to floor height and run the ducting underneath. Any comments on this?
Any help or input would be appreciated. Thanks,
Dave Gaines

Dave Gaines, P.E.

Structural Project Engineer
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