Wood Open Web Truss lateral load connection

[smb4050]

I have a small commercial building using bottom chord bearing open web wood joist @ 16" o.c. spanning 54' with 1/2":12" slope, and bearing on a 2x6 wood wall. Low side heel depth is 32"-36". Not sure what is the most common or economical means to transfer the horizontal diaphragm to the shear wall below. I'd use solid blocking with TJI or solid lumber joist, but the open web joist makes it more complicated. Local truss manufacturer suggested having them build a small framed box that fits between the trusses. Any suggestions or references will be appreciated. Thanks!

 

[BAretired]

You could use a rim truss of the same depth and have the typical trusses butting into it.

Why are you using 16" spacing?

BA

 

[smb4050]

To use a rim joist, wouldn't it have to be the depth of the trusses which is 32"-36" on low side & 59"-63" on the high side? If it's 2 layers of 3/4" plywood, than the roof sheathing would have to be nailed to into the plywood edge. The truss manufacturer isn't real keen about notching the top chord back 1 1/2" for solid blocking.

Short answer to why the 16" centers is making it simpler. 24" spacing will work if I modified the details, but the contractor is geared towards 16" and changing it means I have to change their mindset. I don't know if that's a good answer, but it's an honest one.

 

[mike20793]

I have done as BA stated, but typically I just detail a shear panel I want them to use between the trusses and call out their location on plan, since I often don't need them between every truss. Usually, it just consists of 2x members around the opening with some Simpson RBC clips and sheathing tying everything together.

 

[KootK]

I typically see a continuous 2X6 ribbon set into the end of the truss at the top. Then the wall sheathing is run all the way up and fastened to both the sill plate and the ribbon. I used to be a truss supplier. It's easy as pie.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[smb4050]

On SBCA's website, I found a tech note on heel blocking that shows a in-fill panel, and is likely what I'll use.

KootK, that is what I suggested to the truss mfr, and they weren't keen on notching back the top chord.

Mike, I've used the Simpson's HGA10 in a similar, but the RBC looks simpler.

Thanks for your ideas.

 

[EngineeringEric]

Check plate bearing on a 54' span and i actually see the notched heel on nearly every floor truss that is similar to yours. You could add blocking between and a strap along the top and still use a modified version of Kootk is you truss guy is that complainy.

 

[KootK]

KootK, that is what I suggested to the truss mfr, and they weren't keen on notching back the top chord.

I'd be asking why the heck not or if the truss supplier would like to foot the bill for the shear blocking panels. I used to be the truss supplier. The ribbon system is commonplace and a piece of cake from a fabrication perspective. The top chord isn't really "notched". Rather, it's just just shorter to begin with. Worse come to worse, have them fab the truss 1.5" short and add in the extra vertical block in the field.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[medeek]

The ribbon system is very typical for bottom bearing floor trusses:

I've even seen some with a ribbon top and bottom.

Take a look at the images on Mitek's website:

http://www.mitek-us.com/floortrusses/mitekfloortrussadvantages.aspx

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[Brad805]

If you do have a bearing issue, be sure to watch out for the CP1-6 truss bearing enhancer. It is a terrible simpson product that is very difficult to install correctly, plus one cannot toe nail the truss as one typically does unless you drive nails thru it.