Square Hip Roof with Glulam Hip Beams and Rafters - Will a square tension ring work?

[spencerltu]

Hi all, first post here but certainly not the first thread I've read.

I'm designing an open pavilion approximately 65'x65' with center peak. Roof slope is 4:12. 12 perimeter columns HSS 12x12x1/2 with perimeter beams HSS12x6x1/2 at elevation 10'-0" to pick up the rafters. The glulam design (by others) shows 4 hip beams (36" deep) to the corner columns. The thrust of these hip beams is 89 kips (890 kip-ft moment). My concern was finding a column to transfer that force to the foundation. With that kind of moment, the only column that would work was a very heavy W14.

After speaking with the glulam designer, he said the thrust would be transferred into the perimeter beams as 63 kips tension and they would act as a tension ring. cos^-1(40/89)...I guess. If that's true, the columns will only see the axial force. I'm having a hard time convincing myself that the column won't see ANY of the thrust force.

I can understand the theory, but have any of you ever used a tension ring in a square application rather than circular? This designer has many years experience on me and says he has done it many times. I'm just trying to get comfortable with his design.

Any thoughts/comments are welcomed and appreciated.

Thanks all!

 

[medeek]

If someone can give me an accurate sketch of the arrangement I'll put it into Risa3D and look at the balanced snow load and the unbalanced snow load. I think a visual showing the deflected shape of each load case would be helpful.

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

http://www.medeek.com