Connection to Glulam beam below neutral axis

[smokiibear]

I have a situations where connection jack trusses to the bottom of a 28.5" glulam beam would be convenient. the jack truss is only carrrying 400# at the glulam. I know that shear in cross grain tension below the neutral axis is not optimal. I'm also aware of ANSI/TPI 1-2002/2007 talks about this kind of connection, but does not include glulams and other materials.

Does anyone have any comments on this and/or sources for understanding this type of connection better?

Thanks,

 

[IsaacStructural]

Not much experience with this specific problem, but I was just reading on glulams earlier and I do know that in theory the adhesives between layers and butt joints provide strength equal to or qreat than the base material, so if the theory works for sawn lumber, it should be applicable for glulam. Do keep in mind that the material strength in glulams often varies throughout the depth of the member.

M.S. Structural Engineering
Licensed Structural Engineer and Licensed Professional Engineer (Illinois)

 

[msquared48]

If the jack gtruss is serving as a drag link imparting a tension force to the glulam, is there a member on the other side of the glulam to which a thru-bolt could be attached from the jack truss, through the glu-lam, effectively taking the glulam out of the picture in regard to this force?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[smokiibear]

No...they are not acting as drag struts. Just needing to use Lus410 hangers. There is a vertical load on the hanger, and there is blocking between jacktrussed taking lateral through the diaphragm.

 

[a7x1984]

Your link is broken. Wrap the gluelam with straps?

If I got paid for every hour I worked, I'd be a wealthy man.

 

[smokiibear]

Here is the link again. Sorry about that.

Detail

 

[msquared48]

How is this different with a rafter with a ceiling joist condition? Where is the "truss"?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[smokiibear]

Apologies. Trusses were changed to rafters by the architect. I was just updating the link per A7x1984. I'm still tranfering drag along the axis of the beam from wall above to the sheating on the rafters out to shear walls. Any other thoughts?

 

[msquared48]

Well, you are going to not only transfer the shear in the shear wall to the rafter diaphraqm that spans to shearwalls out of the detail, but also the shear in the floor diaphragm that is nailed to the beam has to get to the same rafter diaphragm.

Just block and nail appropriately for the load path. The nailing of the shearwall plate to the beam should suffice if enough.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[smokiibear]

Yes...the floor, too. thanks. My original concern was just the load below the access. With such small loads, I didn't think there would be an issue. I suppose with higher loads of a few thousand pounds, I'd elect to use a attach above the neutral axis.

Thanks for the help.