strengthening wood beams 1

[abusementpark]

I would like to know what are the most commonly used methods for strengthening a wood beam. The most practical one I can think of would be to bolt a another wood beam to the side of the existing, but this isn't an option in this case. Does anyone have some experience with this??

 

[msquared48]

1. Add a column.

2. Post-tension with steel rods both sides, but this may not be possible as the extra beam option is out.

3. Add steel plates to the side - they would be thinner.

4. Shore the structure and replace the beam.

Are the joists framing into the side of the beam or bearing on top?

Mike McCann
MMC Engineering

 

[abusementpark]

Mike, thanks for the response.

Option 1 is a no-go architecturally.

Option 2 isn't possible as well

I am curious about Option 3. How do you quantify the contribution of the steel plates?

Option 4 might be possible, I'll have to study it some more.

To answer your question, joists are framing into the side of the beam.

 

[STR04]

Look at it as a transformed section, similar to composite steel/concrete design.

 

[msquared48]

Exactly.

Mike McCann
MMC Engineering

 

[Lion06]

Structure Magazine had a really good article on flitch beams a while back. I have a copy at my desk, which I will not be at again until Wednesday. If you want, I'll post it then.

 

[desertfox]

Hi abusementpark

If you are going to place steel plates each side of the wooden beam, then the flitched beam principle as suggested is what you need and if you click on the link below you will find an outline on the principle:-

http://courses.washington.edu/mengr354/jenkins/notes/chap4.pdf

scroll down till you come to page 10 of the above link.

regards

desertfox

 

[SlideRuleEra]

Here is a link to the Structure Magazine article that StructuralEIT mentioned:

http://www.destefanoassociates.com/images/smJune07.pdf

and here is an additional (old) publication on flitch beams from the National Association of Home Builders:

http://www.toolbase.org/PDF/DesignGuides/flitchplate.pdf

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[NS4U]

Can you reinforcing the beam on the top creating a flanged section?

 

[msquared48]

NS4U:

If you have to do that, then you may as well replace the beam with one that works. I can see shoring and a lot of tearout to install a flitch plate on the top.

Mike McCann
MMC Engineering

 

[hokie66]

As your joists frame into the side of the beam, you will have to shore the joists, so you may as well install a new beam or another beam beside the existing. Your OP said that wasn't an option, but maybe you have to make it one.

 

[csd72]

I have seen a proprietary solution where you have a vertical post to the underside of the beam at mid span and then a cable from this to each end of the beam.

No sure where though or if it will work for you.

 

[apsix]

"I have seen a proprietary solution where you have a vertical post to the underside of the beam at mid span and then a cable from this to each end of the beam";

known as a Barrup Truss (in Aust. anyway).

 

[45North]

Working with an old wood beam suggests that it is already loaded, perhaps overloaded?

THe problem with using steel fletch plates or some other composite section is htat you have to deal with the consistent deformation issues. The steel and the wood each take their portion of new load which is distributed proportionally to their relative stiffness. You either have to shore and releive load on the wood beam prior to installing the fletch plates or else check to make sure the wood beam doesn't overload before steel starts to pick up significant load. In other words, if your wood is at 99% of ultimate its going to blow out as soon as you add any additional deflection. No new deflection, no load on the new steel, just new holes in your old beam.

If you have clearance below, one option that may work is Queen-Posting and post tensioning. Its a bit tricky but you can get sail boat rigging that is load rated.

Yeah, you can do it, but in most cases, I think Mike had it right with suggestion #4, just replace the beam.

Good luck.

 

[connect2]

That's excellent 45North.