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