Re: Boring through GLBs

A hole this size wouldn't be a problem anywhere along the beam when bored through the center of its depth.  middle lams are of low rated wood, and are little more than spacers to hold the higher rated wood (flanges, if you will) apart.  Even at the support, you could drive a tight plug in it (not too tight so as not to split the lams).  It would be a good idea if you did that anyway.

JDCoombs

>>> On 12/8/2007 at 11:05 AM, "Donald Bruckman" <bruckmandesign@verizon.net> wrote:

I have a building I designed being constructed here in SoCal which has a clear-spanned GLB floor girder system about 35 feet long with 36" deep beams.  A few weeks ago I got a call from the GC telling me that the electrician, for reasons known only to the electrician, drilled a single 1 ¼" diameter hole through the GLB to fish some conduit through to an elevator room.  After quizzing the GC about where the holes were, I found that they were bored about 10 feet from the point of support and near the center of the depth of the beam. 

 

I was a bit miffed that it happened, but figured a hole that small in the center 1/3 of the depth of the beam away from the area of max moment wasn't going to be a big deal. 

 

Well, my engineer was extremely upset about it and threatened to make them replace the beam. He finally agreed to approve it but I could not get any impression out of him whether it really was a big deal structurally or if he was just putting on a show to teach the GC a well deserved lesson.  Meanwhile, the building inspector gets into the act and is asking for a letter from the manufacturer approving the holes, an idea I found very odd.

 

My question:   What's going on here?  What do I not know, after all these years in the biz, about holes in GLBs?  From a reduced section standpoint, away from the point of max moment and near the center of depth, such a small hole seems relatively unimportant to me. Am I missing something?

 

-DB