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RE: allowable hole in wide flanged beam

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I was taught to also specify that a field cut be done using a template
(i.e. don't let the torch guy go hog wild) and also make sure all corners
are rounded (that typically goes with out saying).


On Thu, 5 Apr 2001, Jones, Mark A wrote:

> I worked for the Navy for a number of years.  EVERY beam had holes to
> lighten them.  Most "Land" Structural Engineers seem to have a fit about
> putting holes in a beam.    I have to chuckle given the quantity we used and
> the loads those beams saw.  It's not that big of a deal IF you put them in
> the right place.  I don't have any references for you but here are a couple
> of rules of thumb.  Basically, you are taking advantage of the neutral axis
> by removing material in the area of VERY low stress.
> 1) Holes are BAD in shear zones.  Hence, never put them in bearing areas and
> under concentrated loads.
> 2) Rule of thirds:  If you keep them in the middle third, both ways, you are
> ok.
> 3) Limit the diameter of the hole to 1/2 the beam depth.  
> 4) Keep the hole circular or semi-circular (hexes and octagons).  I've seen
> ovals for ducts but I would always calc these.
> 5) Space the holes 1.5 - 2 times the diameter.
> 6) Smooth the edges.  If you field cut, which I don't recommend, make sure
> they grind the hole smooth not just remove the burrs.
> If we were concerned about a particular hole, then we would draw the shear
> and moment diagrams (remember those?) for the beam, then check the reduced
> section at the point of the hole.  Computing the reduced section should be
> easy if you keep the hole centered and it's not that hard if you keep it in
> the web.  
> Holes in the flanges are a completely different story as Jason pointed out.
> Mark Jones
> Jacobs Engineering
> Structural Engineer, formerly a Naval Architect.
> -----Original Message-----
> From: Pat Clark [mailto:bcinc(--nospam--at)]
> Sent: Wednesday, April 04, 2001 4:31 PM
> To: seaint(--nospam--at)
> Subject: allowable hole in wide flanged beam
> What kind of references are available for designing holes through the web of
> a wide flange beams.  Should I just check a reduced section, and moment of
> inertia?  Is there any code references? Any help would be appreciated.
> Pat Clark, P.E.