Steel Beam Penetrations (Sizes and detail?) 1

[davab]

Fellow engineers,

I am running into a problem in the field where beam penetrations through my steel beams need to occur. Our detail shows that the depth of the penetration can be D/3 (D = depth of steel beam) and the length of the penetration is 3/4*D.

This rectangular penetration has fillet welded plate top, bottom, and sides.

Is this somewhat of a generic penetration requirement that every engineer uses or does anyone use different (whether it is more or less stringent) than what I have described above?

I am curious to know because unfortunately, I might be forced to provide bigger penetration than what is described above and I am trying to understand where my comfort zone lies.

Any thoughts and/or suggestions would be appreciated.

 

[skeletron]

From some notes I have (CISC):

Check your beam class. Class 1 and 2 only for holes.

Circular holes are easier to fit in. Put them in the middle third of the web and in the middle half span of the beam. No holes under direct point loads. The hole size is limited to d/3 and a second hole can only be placed greater than 2.5 x diameter(larger) away. Shear at the support must be <50% Vr.

Rectangular holes are a little more complex. There are proportion rules (something like 2.2 to 1.0 OR 3.0 to 1.0) and there are also for the stability of the compression flange. Haven't really reviewed this area of the manual, but it seems like more often than not a rectangular hole will need some reinforcing.

 

[KootK]

I might be forced to provide bigger penetration than what is described above and I am trying to understand where my comfort zone lies.

I'd get yourself a copy of the document below, fire up an Excel or Mathcad sheet, and let the numbers be your guide to where your comfort zone should lie. At the end of the day, a structural engineer's "judgement", should primarily be the culmination of numerical evaluation work performed in the past. It's not as though humans are born with native intuition for these thing. Toss in some experience and the opinion of your learned colleagues and that's pretty much the whole "judgment" recipe.

It is common for firms to have a generic "works in most situations" detail like what you've described which, when exceeded, triggers a true numerical evaluation. The attached document also has some design aids that expedite a hand calculated design procedure.