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RE: Openings in concrete beams

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I'm glad to hear from you.
I've done a lot of deep steel beams with large opening in them.
For those It's simple static.
For RC beams, depending on your beam depth and size of the opening, in addition to calculation of the section properties you would also want to detail it with add'l diagonal rebars fully developing well back into the solid section of the  beam.

Casey (Khashayar) Hemmatyar, SE

From: Gaines, David [mailto: David.Gaines(--nospam--at)]
Sent: Friday, December 07, 2007 11:57 AM
To: seaint(--nospam--at)
Subject: Openings in concrete beams


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
HDR ONE COMPANY | Many Solutions
251 S. Lake Ave, Suite 1000
Pasadena, CA 91101
T: 626.584.4960
F: 626.584.1750
email: david.gaines(--nospam--at)