Replacing a load-bearing beam

[dpb]

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Yes, see below for more on that...

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Indeed, that's where I was confused before...I had misunderstood and thought this U was the full-length beam replacement and were trying to figure out how to get it in place on one end. I couldn't figure out how, since the main load was, as you say being carried by the columns one needed anything anyways near that stout as the intermediate beam between them. That it's a gusset plate I can go with at the dimensions.

But, that leaves me w/ the problem of not understanding what's the issue in the installation I think.

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No, I don't think that would work; what I was envisioning was a full length side plate of (say) 1/2" x 10" bolted thru the existing beam to handle the longer span w/ the upstairs load handled by the columns.

I thought your original proposal was to replace the existing beam in its entirety and my suggestion was to leave it in place and rather than put something underneath it over the existing column to trim the joists and rehang them leaving the vertical primary support on the column.

I think there's still some talking past each other owing to each having a vision but not a common set of drawings/concepts...

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Always is when get an engineer involved... ;)

Altho I commend you for getting somebody to actually look at the situation given the nontrivial nature of the loading distributions and particularly that discontinuous beam that complicates things.

Good luck; knowing the guy didn't try to fit in a full-length U to bridge the gap and claim it had a stress problem makes me feel much better about his doings...I believe it for the 1/4"T short section to hold the end moments; I wasn't so sure when presumed it was much heavier material and full length.

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[Phil]

Yes, the main confusion comes from the fact that my original question was not about this plan. I was asking about a different plan that I'm considering due to the problems with this solution.

Plan 1: 2 columns (4 and 20 feet) under ground-floor columns with steel U supporting the beam's gap Plan 2: single column @ 16 feet with beam replacement. (this post was about this plan)

Ideally, I'd have a single column @ 16 feet, but this doesn't seem possible without replacing the beam.

Thanks again, Phil

[jamesgangnc]

What's the distance in the other directions, aka 90 deg from your beam. Is it possible to put a smaller steel I beam 90 deg in place of the column you want to remove?

[Phil]

Interesting thought!

The house is 20 feet wide and the beam is not exactly in the middle. I'm not at home currently, so I can only estimate that it's 8 feet from one wall and 12 from the other.

You're suggesting that the column at 4 feet could be replaced by a 20 feet long steel beam?

Thanks, Phil

[jamesgangnc]

Yea, but I was hoping for a shorter distance :-) Oh Well.

[Wayne Whitney]

[Also, from previous posts, there is a column coming down at x = 4 feet carrying half the load from a 16 foot span of floor joists for the second story.]

The only difference between these two plans is the column carrying the second story floor joists. The load from the first story floor joists is the same in both case, 16 feet of span. But in Plan 1, the ground floor column is above your basement column, while in Plan 2, the ground floor column hits the basement girder 4' from the basement column, imposing extra bending moment on the girder.

By my calculations, which I am not qualified to do, that extra point load increases the maximum moment in the basement girder by a factor of 25/16, or plus 56%. [Assuming the floor joist loads for the first and second story are the same.] So unless your steel flitch plate solution for Plan 1 is at the edge of what is feasible, I would expect it to be possible to do Plan 2 the same way using more or thicker flitch plates.

Of course, there may be other irregularities not presented, or there may be a difficulty in making the connections properly in Plan 2. Your structural engineer should be able to tell you.

Cheers, Wayne

[dpb]

Sounds about right. My thinking, (again, w/o _any_ calculations :) ) while a little more installation effort, was to extend the side plate the full or nearly the full distance and beef it up to 3/8" or even

1/2". I'm pretty confident that would handle the deflection pretty easily if the vertical loads are on the columns, wherever he chooses to end up putting them.

But, he's got an enganier who's gettin' the big bucks and my registration ain't no good anywhere but TN and here and I'm not working anyway (other than farming again, that is)... :)

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[DD_BobK]

dpb-

Great minds think alike........... flitch plates with a piece of angle iron or channel welded on to serve as a joist seat.

I would suggest using plates both on both sides (symmetry & all).

Rather than bolting through I would recommend to your engineer that plates have offset hole patterns & use Simpson SDS 2 inch "lags". They usually can be installed without pre-drilling unless the timber is very hard / dry.

Make sure hole pattern considers joist locations.

OP- You didn't give the exact dims of the 3x12's (true 12" or 11.25"?) or the depth of the joists (2x8's?) but my rough calc says that plates (1/2" x 12") both sides should just about do the trick.

Tell your engineer that "through bolting sucks", results in a very sloppy fit up and removes too much material from the original member The Simpson SDS are the way to go.

How about some photos?

cheers Bob

[bambam]

Huh????

Either trust your engineer, or hire a second one as a double check.

Do you not intend to get a permit and a municipal inspection for this job???

My city would require an engineer's drawing and an engineering sign off on the correctness of the work carried out for the type of structural alteratrion you contemplate.

Incidentally, the job you outline is neither unusual nor complicated. Pay an engineer!!!

Ken in calgary.

[DanG]

If you intend to remove the existing wood beam, you will need to build a temporary wall on each side of the beam that will carry the load while you remove and replace. Getting a beam of size into location and situated where it can be lifted into position are usually the hard part. There was a similar project taken on this past year in JLC.

This one is your project exactly:

Here is one other approach:

Here is another, though you may have to pay to access the archive

[Phil]

I was referring to the contractor, not the engineer.

Same here. But the engineer's plan will layout the result of the work, not exactly how the work should be carried out. For example, it says that proper support must be put in place during the work. It doesn't say how to put that proper support in place.

By posting here, I was hoping to get an insight on how to properly execute the plan. I want to be able to verify that the contractor's solution is sensible.

Cheers, Phil

[Phil]

Thanks! This is great stuff! Didn't know about JLC.

Cheers, Phil

[Phil]

The 3x12 are probably true 12 feet, but it's hard to know for sure due to the fact that they're not completely visible (haven't torn down everything yet).

I did measure the joists, but can't remember off the top of my head. I think they're 2x12.

You're saying that with a single column @ 16 feet and 2 1/2" plates of 12 feet along the beam should hold up? There's a split @ 12 feet in the beam, so would these new plates span 6 feet on both sides of the split?

Is this achieved by the use of the SDS instead of bolting through, or is that a separate concern?

The engineer's current solution is 1/4 inch U spanning 20 inches on both sides of the split, but requires 2 columns: @ 4.5 and 20 feet. The U would be bolted through the member with 9 1" bolts on either ends.

Interesting, I'll see what he has to say about this.

I'll see what I can do.

Thanks! Phil