******* Electricians 6

[SteelPE]

So, I designed this multi family house over a year ago. Construction has been slow. I was last at the house 5 months ago with framing complete. Now, 5 months later I received the attached photos:

So the electrician in his infinite wisdom decided it was best to drill through one of my fancy LVL's vs bringing his conduit down at the perimeter wall of the house. Now I have been tasked with accepting the situation, or fixing the situation.

The GC has given me the position of the pipes in relation to the end of the beam. Other than checking moment and shear at this location for the reduced section, what else can I do?

Reinforcing of the beam is going to be incredibly difficult as we used CCQ style caps on the columns (meaning "adding another ply) is going to be incredibly difficult. I may be left with the option of adding a column under the hole.... but I don't want to do that unless I have to (although I would love to do it out of spite).

 

[phamENG]

Post under the hole is a bad idea - you'll put the hole in tension and that'll cause problems.

Since it passes through the top of the beam, there's not a lot you can do. Maybe some fancy steel weldment that can slip on and be screwed into place? Short of that, the damaged plies probably need to be replaced.

 

[SteelPE]

Pham,

I get your point about tension in the hole.

However, if the beam was 10' long working as a simply supported beam what difference does it make if it's 5' long and we say it's working as a simply supported beam? That is, I know tension may cause damage to the beam... but if the beam does end up cracking it will work as a simply supported beam.... so it doesn't matter. Not a great situation but not terrible either.

 

[Celt83]

However, if the beam was 10' long working as a simply supported beam what difference does it make if it's 5' long and we say it's working as a simply supported beam? That is, I know tension may cause damage to the beam... but if the beam does end up cracking it will work as a simply supported beam.... so it doesn't matter. Not a great situation but not terrible either.

With the LVL it will be more of a tearing action that depending on how the effective grain works out could propagate down the length of the member.

Also you may want to double check they used proper bolts to attach the plies together and not carriage bolts (those rounded heads in the picture look like the latter)

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[Enable]

I can't speak for phamENG but I would be worried about the timing of events with respect to serviceability, not ultimate by putting the post in. So you put the post in and because of lack of superimposed dead load or the design live load being applied or whatever the beam seems to work. Then finishes go on and now you have floor tiles, still an intact beam. But then a party happens and all of a sudden the tension causes that hole to split and we have new, large deflections in spans (opposite sides of the post) where they were not present previously; tiles / finishes get fuckulated and SteelPE gets a rather annoying callback.

 

[dauwerda]

If the additional post is the solution and you are that worried about the tension in the top, just cut the beam in half on top of the post, problem solved.

In general, wood is much stronger in compression parallel to the grain than it is in tension. As this section loss is in the compression zone, is it small enough that the beam still checks out? It's obviously not ideal, but I'm guessing its not detrimental either.

 

[GC_Hopi]

Depending on the loading, you could try sistering on steel plates or wood. Probably should have the electrician remove the offending conduit as a start.

 

[SteelPE]

I guess at this point..... other than checking shear and moment in the beam at this point, what other checks would you do?

 

[GC_Hopi]

Deflection...

 

[kipfoot]

I don't think I'd be too concerned with the negative moment over a new post, if that's what you need. As long as you check it as a continuous beam and not two simple spans. You'll have 1/4 the bending moment at the support (compared to the full simple span), so presumably the stresses will be very low and not risk the flexural tension failure of that bit of LVL above the hole.

It's a bit of an esoteric approach, but like dauwerda suggests, you could snip that bit of lvl with a reciprocating saw in about 2 minutes. Though, you just have to explain how you'll have a better and more reliable structure by cutting part of it away.

(Also a word about electricians: I find that they're usually the smartest people on the site. So, the plumber must have some satisfaction that it wasn't him this time. I don't even know whey they'd need conduit in this case.)

 

[phamENG]

Celt and Enable picked up on my concerns, and dauwerda has a great solution if you decide to put in the post.

In terms of checking the adequacy of it as is, I would look at it as if there is a notch through the whole beam at that point. APA has an LVL Hole Drilling guide, but it would be good to check the literature from the manufacturer (I don't see a logo in your pictures).

General guidance is this:

When necessary to cut a small notch in the top of an LVL beam (in the compression side) to
provide passage for small-diameter pipe or conduit, the cut should be made in an area of the beam
stressed to less than 50% of the allowable bending stress. The net section in this area should be
checked for shear and bending stresses to ensure adequate performance.

 

[rb1957]

can you reinforce the web ... and coincidently block his conduit ?

another day in paradise, or is paradise one day closer ?

 

[Celt83]

The article by Franke and Harte on Failure Modes and Reinforcement techniques is pretty good if you want to put numbers to it. Link

Also This New Zealand Resource: Link

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[sandman21]

Take solace in the fact that the electrician is blaming you, as engineers never know how things "really" work in the field.

 

[IRstuff]

Adding the column won't spite the electrician, since he's long gone, but it will annoy the owner forever.

But, it could be worse; in San Francisco, many warehouses have been converted into condos, and I recall one sales photo that shows a diagonal beam coming out of a cabinet in the kitchen, heading down to the floor in the middle of the kitchen, yeesh.



TTFN (ta ta for now)
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[XR250]

It might be fine as is. Have you checked strength? Deflection has likely not been affected too much as the compromised section is small. Its a round hole so stress concentrations are probably pretty low.

 

[BAretired]

Also a word about electricians: I find that they're usually the smartest people on the site.

Hopefully, that was not the case in this instance.

BA

 

[Ron247]

Does it calculate to be ok as is when checking moment, shear and deflection?
The picture looks like they messed up one layer and maybe part of a 2nd, is that correct?

In the first picture, the wall under the beam appears to be load bearing. I do not see a gap between the beam and wall. So other than the wall now must remain in place, I do not see a problem.

 

[Aesur]

Probably not going to be a popular response here, but ask them how much they are willing to pay you to engineer a fix for their mistakes. Depending on the fee, determines the amount of work you put into this, could be "replace the beam", "add a column", "strengthen the beam" or dig into tons of research and go theoretical on this and check if it's even an issue, let what they are willing to pay you determine which solution you give. If contractors don't feel the pain when it comes to their mistakes they won't learn to pay more attention and hold their subs more accountable.

 

[IFRs]

Would it help to remove the pipe and fill the hole with epoxy?