Patchwork of holes in the web of a steel beam

[gcs3pe]

Ahhh contractors. I was brought onto a site where a 24' long W10x88 has been installed flush in a ceiling and the contractor has taken some liberties with pipe penetrations (see attached).

A quick beam analysis shows no real issues with the selection of the beam - it's effectively uniformly loaded (deflection controls by a wide margin, shear and moment are covered in spades).

The photo shows a 3" pipe and two 1" pipes that apparently need to pass through the beam. The wood packing the web flush to the flange edge (for face mount joist hangers) has been attached with 1/2" bolts staggered at 16" on center. Unfortunately, one attachment hole is clearly in the mix with the other holes.

The holes for the pipes are 5", 2" and 1.75" in diameter, and they were created with the engineer's favorite tool - the acetylene torch. The three small holes (two pipes/one bolt) are so close that they should probably be taken as one large hole. And the torch cutting discounts what, another 1/4" of steel all around?

This condition occurs 10' from one end, so shear is relatively low at this location. The center of the large hole is above the neutral axis, and the three small holes are not far from the bottom flange. The beam has so much shear and moment capacity (525% and 100% excess, approximately), that my primary concern goes to the deflection.

Any suggestions for a decent analysis of this issue? Any down and dirty field-type solutions come to mind? This is a residential project, extremely budget sensitive, and taking that beam out will send the owners off a cliff.

 

[ishvaaag]

You can calculate the loss of inertia at the worse point and create a 3 segment beam with the restraints at ends, load it and see the deflection. Or more segments, representing the issue from an inertia viewpoint.

As easy as that is to model it 3D in fem today, and any of the two may give you an appraisal of the situation.

 

[connectegr]

Another small concern...
The holes appear to be torch cut and jagged. They should be ground smooth, to prevent stress concentrations and to avoid perpetuating cracks.

http://www.FerrellEngineering.com

 

[BAretired]

I agree with grinding the holes to remove stress risers. It might be a good idea after grinding, to reinforce each hole with a short length of pipe welded to the web.

BA

 

[SkiisAndBikes]

The Canadian Handbook of Steel Construction has a section on web openings including formula's for reinforced and unreinforced web openings. The fomulae are for beams of class 1 and 2 sections with openings between 0.3 and 0.7 x depth of section.

Horizontal reinforcing plates are usually welded above and below the openings.

CISC guideline - The corners of the opening should have a radius at least 16mm or twice the web thickness, whichever is larger.

 

[apsix]

The above advice is good practice, but the excess capacity is such that I would probably just let it go as is, seeing that it's a residential property.

The 20% (rough conservative guess) reduction in stiffness over 1 ft will only affect deflection by a few % and shouldn't be significant.

 

[csd72]

At one of my previous employers we once forced the contractor to reinstall the beam just to make an example of it (the beam probably just worked). It should be reinstated at the contractor expense anyway as they have carried out modifications to the structure without approval.

We bend over backwards too often to make these things work in my opinion.

 

[SteelPE]

csd72

I often fantasize about making an example out of projects but have never done it.... those steel erectors are all to often very large people.

 

[csd72]

You need to develop a thick skin.

Concretors are big too. I once had to tell a site full of concretors and steel fixers that they still had several hours of reinforcement to install before they could leave for their long weekend. They had all their boats and caravans lined up outside ready to go - I think they were contemplating throwing me down the nearest hole!(lucky that most of those were already filled with concrete).