Wood built-up-beam connection to wood post 1

[ajk1]

I am reviewing a cottage that was built last year. One of the items I am concerned about is the detail at the top of the wood post. I have prepared the attached sketch of the interface of top of wood post to underside of the wood beam. The load bearing exterior stud wall has no exterior face sheathing, and sits on top of the 1st floor joists which in turn sit on a a 4-ply wood beam (4-2x12's) which in turn sit on top of a 5½ x 5½" wood post. Connections are only toe-nails. Is that how that would normally be done? It seems a bit wobbly and not particularly effective against uplift forces.

Questions:

1. Should there be a metal strap from the built-up wood beam to the post, or a metal bracket fastened to the top of the post and the beam?

2. The built-up wood beam spans about 11', and alternate plies are spliced within the spans. Does the built-up wood beam require any lateral bracing to its bottom?

 

[msquared48]

Simpson makes post to beam connectors. Perhaps one could work for your application. It is normal to provide one for decks or exposed roof conditions


Mike McCann, PE, SE (WA)

 

[Jerehmy]

A personal cottage likely falls under the IRC prescriptive design. I'd check that and see what the minimum connections are. A lot can be toenailed.

Also, I can't open that file. Is it a photo?

 

[ajk1]

ok.

It is not a photo. I will try attaching again now.

 

[BAretired]

Toenails may be normal for some contractors but it isn't the way it should be done, particularly if you have uplift. You should select an appropriate connector capable of resisting your uplift forces.

BA

 

[msquared48]

This is a brace connection that will generate tensile uplift forces due to the geometry alone, aside from any wind uplift. Toenails are not good for tension connections and marginal for shear. Use the beam to columns plates for the loads needed as BA said.

Mike McCann, PE, SE (WA)

 

[ajk1]

I realize that the diagonal generates up force, but that is countered by the dead load of the floor and load bearing wall above, so that is not the part of the connection that I am[highlight #FCE94F][/highlight] concerned about. I am more concerned about the fastening of the built-up beam to the post of which it sits. I will check if there are any net uplift forces, but if there are not, then the question is, are the toenails from the built-up beam to the post sufficient, or should a metal strap be added just to have a positive tie? Please keep in mind that I am reviewing something already built (by others). I personally would not have built it like this.

 

[msquared48]

Regardless what you do, do not rely ONLY on toenails for anything.

Mike McCann, PE, SE (WA)

 

[BAretired]

As it stands, the post and beam together form an unstable member with three hinges in alignment, not perfect hinges admittedly, but close enough. That brings us to your second question. Bracing the top of post or bottom of beam back to the joist would be another way of stabilizing the post and beam but of course would not help in resisting uplift.

Please keep in mind that I am reviewing something already built (by others). I personally would not have built it like this.

I don't believe this matters at all. If you would not have built it this way, tell the client how you would have built it and what he should do now to bring the structure to an acceptable condition. Personally, I would recommend appropriate hardware connecting post to beam but your recommendation must be based on your best engineering judgment.

BA

 

[ajk1]

Thanks msquared and BAretired.

Very good advice...I especially like the point about hinges...that is really what I was trying to say, but you stated it much better than I. Much appreciated. Just one little point ... and please don't take this the wrong way, because your advice is very much valued and appreciated...about whether it matters whether I designed it or not. In my opinion it does matter in the sense that I have a professional obligation to mitigate the damages. When I used to act as expert witness in litigation cases, the construction law lawyers said that "repair" was different than "new design". In other words, even though I would not have designed something the way it was designed by others, the question to be dealt with is whether what was designed figures in accordance with sound engineering principles. The standard is what would the reasonably prudent engineer have done, not what the exceptionally brilliant or very cautious engineer would have done. If I recommend remediation that can be shown not to have been necessary, then I will become liable for the cost of those repairs, and I think that is only fair. So in this case, I have to set aside what I would have done, and evaluate what has been done by others.

Again, thanks very much for your advice about the hardware and that is what I am going to recommend.

 

[Jerehmy]

I can open it now, thanks.

I agree with everything everyone said, just thought I'd throw in my 2 cents.

My comment about the toenailing was in regards to the joists resting on the beam, not the beam/post connection. Thought I should clarify. Also, I didn't see the detail til now.

Is this exposed to the weather? Is "rock" grade?

Is the post attached to the pier in any way?

Is the beam continuous over the post? With negative bending over the post and the cantilevered wood column, which is terrible, I'd want the bottom of the (4)2x12 braced somehow. Maybe with a 2x12 glued and screwed to the joists, then run it down to the 4ply beam. One on either side of the post. Attach the blocking to the beam with HGA10 Simspon connections(by far my favorite simpson product). Or maybe run a 2x4 vertically, 2x4 at an angle as a strut then have a plywood gusset connecting them together. Then use the simpson connector to attach it to the beam.

OR run a horizontal member from the strut to the top of the post. This is in addition to a simpson post cap.

Maybe JUST use a simpson cap. I don't know if I'd be comfortable just using a cap though. The cap would have to "fix" the beam to the post to get rid of the hinge that BA was talking about. Maybe there are other connectors that I can't think of that will make this setup more stable.


I would look at it this way:

Let's say there's a point load at the bottom of the beam/top of the post. How do you have to brace the beam/post to make the system stable?

Also, per NDS you need restraint against torsion at the beam/post connection.

 

[BAretired]

@ajk1,
I agree that "repair" is different than "new design". The main difference is that in repair, you do not have the luxury of changing the existing structure unless it is so bad that demolition is easier and more cost effective than repair.

If you have been retained to specify repairs to an existing structure, the professional responsibility for the work rests with you, not with the original engineer, assuming there was one. You are no less responsible for the repair measures you specify than you are for the design of a brand new structure. So, in that sense, it does not matter whether you designed the original work or not but I agree that you have a professional obligation to mitigate the damages; I can't imagine a recommendation of suitable hardware in the present case could be construed as failure to mitigate damages.

BA

 

[ajk1]

ok, thanks