Wood I-joists repair 3

[reverbz]

Hey Guys,

I am trying to detail a repair for wood I-joists where the top chord is partially notched. IS there a common fix for this? I'm thinking of sistering 2x's to develop the compression load through and then back into the member but would like to hear what other people have done.

Thank you!

 

[ChorasDen]

I'm curious to see what the general audience responds with on this one before I fully comment, but I would avoid the approach of:

thinking of sistering 2x's to develop the compression load through and then back into the member

this assumption is not typically effective nor achievable. Wood i-joists typically do not behave in such a manner where we can take load into and out where ever we want. Stiffness controls how that load moves.

 

[phamENG]

I think it depends on how deep the notch goes. If it's all in the top chord, I can get behind your approach. But if the connection of the web to the top chord has also been damaged, I think you need to be a bit more holistic in the repair. In that case, I'd likely go for packing the webs flush with the chords and then sandwiching it with structural sheathing.

I-joists tend to be pretty fragile. They are great products when used properly, but are very problematic if they aren't.

 

[XR250]

I-joists tend to be pretty fragile. They are great products when used properly, but are very problematic if they aren't.

I think it depends on how deep the notch goes. If it's all in the top chord, I can get behind your approach. But if the connection of the web to the top chord has also been damaged, I think you need to be a bit more holistic in the repair. In that case, I'd likely go for packing the webs flush with the chords and then sandwiching it with structural sheathing. I-joists tend to be pretty fragile. They are great products when used properly, but are very problematic if they aren't.

Yea, that's the problem I have with them. I only spec them when requested or they make some sense in the application. They are fine in a perfect world that does not actually exist. Make renovations harder, do not tolerate abuse from trades well, do not handle moisture well, buckle at loads much lower than stated. For top chord repairs, it really depends where along the span it is. Many times, i will just add a 4x4 post on a footing.

 

[DoubleStud]

Flange Notches in TJI Joists - tb-818

Technical information for repairing TJI joists with side top flange notches

www.weyerhaeuser.com

 

[reverbz]

I think it depends on how deep the notch goes. If it's all in the top chord, I can get behind your approach. But if the connection of the web to the top chord has also been damaged, I think you need to be a bit more holistic in the repair. In that case, I'd likely go for packing the webs flush with the chords and then sandwiching it with structural sheathing.

I-joists tend to be pretty fragile. They are great products when used properly, but are very problematic if they aren't.

Interesting approach. In this case, the chord is the only part notched and it isn't interfering with the connection to the web. I'm also planning to have them jack up the joists 1/8" while they install to help with the slip issue. Just out of curiosity: what would you pack it with? I like the idea of the sheathing on the outside over the chord and packed web. Would it be packed with sheathing as well?

 

[reverbz]

I'm curious to see what the general audience responds with on this one before I fully comment, but I would avoid the approach of:

this assumption is not typically effective nor achievable. Wood i-joists typically do not behave in such a manner where we can take load into and out where ever we want. Stiffness controls how that load moves.

I understand it's not ideal in theory. To help with this, I'm having them jack up the joists 1/8" during the repair to help with the slip issue. I still think this is practical and justifiable. I'll think it through a bit more but I believe I've seen similar repairs before( I get it that doesn't make it right but I don't think everyone is just straight up replacing these for a tiny notch in the top chord)

 

[phamENG]

Would it be packed with sheathing as well?

Depends on the size of the chord. The document DoubleStud posted is essentially what I do when it comes up.

 

[ChorasDen]

What most fail to realize is that when a compression flange on a wood i-joist is repaired, we are not somehow magically taking the load out of the flange, diverting it around the joist, and then magically putting it back into the flange at whatever location we see fit. If that were the case, there would be no tension or compression couple within the flange (we took that load out and put it into the repair), and thus no fiber elongation, and therefore, no deflection at this location. To simplify, there is significant difficulty getting the load out of the flange and into the repair member, due to the significant stiffness difference and connection methodology of the repair member compared to the original joist.

What compression flange repairs typically provide is a reduction in the joist failure mode, which is typically euler buckling at the reduced section of flange (combined with the induced eccentricity from the notch). The repair helps to provide additional buckling restraint for the reduced flange section, but it does not typically return the joist to full strength. There are ways to achieve full strength, or near full strength, but they require significant composite action development of the repair, as well as resolution of the eccentricity to prevent failure prior to achieving allowable design loads.

 

[RontheRedneck]

Something similar to the table that DoubleStud linked to should be available for most any manufacturer. I'd suggest going with their recommendations rather than reinventing the wheel.

 

[dik]

Make renovations harder, do not tolerate abuse from trades well, do not handle moisture well, buckle at loads much lower than stated. For top chord repairs

and can be a real problem when subjected to a fire.