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RE: Openings in concrete beams

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The portions of the beam above and below the opening are designed for their portion of the flexural and shear stresses, at the point of the span where the opening occurs, based on each section’s relative stiffness. The portion of the beam at each side of the opening is then designed for Vierendeel action.  Lastly, you must analysis the deflection of the beam based on the variable inertia of the beam in combination with the Vierendeel distortion.


D. Matthew Stuart, P.E., S.E., F.ASCE, SECB

Senior Project Manager

Structural Department


200 Route 9

Manalapan, NJ 07726

732-577-9000 (Ext. 1285)

908-309-8657 (Cell)

732-298-9441 (Fax)



-----Original Message-----
From: Gaines, David [mailto:David.Gaines(--nospam--at)]
Sent: Friday, December 07, 2007 2:57 PM
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)