1.25" hole in existing metal building frame column and portal column

[braves25]

Hello all,

I am needing to drill a 1.25" dia. hole thru the web of a metal building main frame column and thru the flanges of a portal frame column. My attempts to avoid this issue failed. There is no "give" with regards to hole placement. Portal frame flange is 8" wide....I have 3.5" from inside face of web to the edge of the flange (1.25" hole to be centered on the 3.5" dim.). Hole will be cut thru the web of the main frame column about 6" from the flange of the main frame column. With this being an existing metal building, I do not have a good feel for the exact loads on these two members. My thought was to reinforce the web and the flanges with equal to (or greater than) the thickness of the web and flange being drilled thru and then developing the steel past the hole to transfer the forces. Thoughts? Suggestions? Thank you in advance!

 

[PaulRansom]

As you have ruled out the option to not do this ... Without qualification for the stress state of either the flange or web, that's your task, it is reasonable to reinforce as suggested. Note that the reinforcement of one side of the flange is a little tricky since it will create an eccentric local stiffness irregularity - that's a big piece of flange to remove - and reinforcing with a cover plate with same hole does not improve that. You could drill and reinforce both sides of the flange, equally. Web shear is typically low. Check shear lag in sizing cover plates.

 

[ajh1]

Some of this is a function of how high up the building column and portal column you are at. Most portals on metal buildings tend to be fixed knee and pinned base (as opposed to a wind post that is a fixed base), so a hole near the floor is going to have minimal moment in the portal frame column while a hole near the top of the portal is going to have significant moment forces. Normally portal frames are used in situations where there has to be a wall opening in that area that would be infringed upon by rod bracing. If you are running a pipe through your hole it would seem that could also interfere with the clearances required. For the main building column, shear forces are going to tend to be higher near the base. In all cases, it is a good idea to do some reinforcement work.

 

[KootK]

Certainly, reinforcing is an option. That said:

2) It's a pretty rare steel column web that's so heavily taxed in shear or squash that the addition of, effectively, one large bolt hole is going to doom it. I'd be inclined to not sweat this.

3) For the beam flange, my first stop would be evaluating it like any other bolt hole, albeit with consideration of the process used for making the hole. If flange axial capacity based on rupture stress with the hole exceeds flange axial capacity based on yield stress without the hole, no reinforcing required. I'd be inclined to put the hole as close to the beam web as you can get it if you have say in the matter.