Hip Roof
Hip Roof
(OP)
Hello Guys;
I am currently working on a patio cover, please see the attached sketch. The architect wants me to remove two interior beams where the king posts are landing. I have seen several hip roofs without interior supports, but I just don't get how they are working. It seems that the diaphragm is somehow holding the roof together, but how do I calc this out.

Any ideas, I will appreciate them.
Thank you.
I am currently working on a patio cover, please see the attached sketch. The architect wants me to remove two interior beams where the king posts are landing. I have seen several hip roofs without interior supports, but I just don't get how they are working. It seems that the diaphragm is somehow holding the roof together, but how do I calc this out.

Any ideas, I will appreciate them.
Thank you.






RE: Hip Roof
RE: Hip Roof
RE: Hip Roof
I think it can possibly still work but you'd have to think it through.
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RE: Hip Roof
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.
RE: Hip Roof
Mike McCann, PE, SE (WA)
RE: Hip Roof
Regards
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RE: Hip Roof
You need a ring beam capable of transmitting axial tension and compression across the corner joint and up into the rafters. That ring beam could potentially be just your top plates if detailed correctly. I guess it's less a ring beam than a ring tension tie.
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.
RE: Hip Roof
It will also let you keep you ridge. Although, I doubt a short ridge like that would make Kootk's idea unstable.
RE: Hip Roof
Without the ridge beam, it is just a two way arch with a pin at the ridge.
Mike McCann, PE, SE (WA)
RE: Hip Roof
RE: Hip Roof
RE: Hip Roof
Mike McCann, PE, SE (WA)
RE: Hip Roof
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.
RE: Hip Roof
if ridge eliminated, i'd design as others said above and for constructability i'd look at a peak connection made with something like 1/4" or 3/8" custom fabricated steel bucket and bolt system connecting two diagonally opposite hips together as a stable standalone system first and then 'hanging' from that the other two hips also supported by buckets shop welded to the others, ie all one fabricated piece. i'd probably specify tight fit everywhere to take the compression but design the bolts to take all the compression too. you could add a square non structural fill plate from the underside where the 4 buckets converge to get a nice symmetrical look from below.
if i'm see it right, the tension ring at the bottom seems complicated by the design with the rafter over the tension ring beams...the lateral component of your hip thrust is above the centroid of the tension ring members introducing a vertical plane moment at this condition. perhaps a deeper hip beam combined with a shallower rafter can get the eccentricity to a palatable point, or perhaps you introduce a shallow steel member, so not too obvious, affixed on top of the perimeter beams and aligned with the centroid of your hips to act as the true tension tie.
RE: Hip Roof
If with unbalanced snow loading the tension in the tension ring would be the same all around or not?
Mike McCann, PE, SE (WA)
RE: Hip Roof
RE: Hip Roof
Mike McCann, PE, SE (WA)
RE: Hip Roof
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.
RE: Hip Roof
RE: Hip Roof
Mike McCann, PE, SE (WA)
RE: Hip Roof
Considering how short the ridge is and the need to make a moment connection of it, perhaps that entire 2' chunk should just be steel.
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.
RE: Hip Roof
Mike McCann, PE, SE (WA)
RE: Hip Roof
Also, has anyone had much success with wood moment connections period? Most studies I've read and connections I've seen in person have a problem with excessive rotation before any moment is transferred.
RE: Hip Roof
RE: Hip Roof
I was thinking of something like the detail below. As XR250 alluded at the top, the demand here would be nominal. Additionally, as you pointed out, the issue with wood moment connections tends to be deformation. And this particular connection wouldn't be too sensitive to that. I wouldn't do this for a serious moment connection.
In general, I agree with these sentiments. My wife's firm actually runs a brisk trade doing side work as timber connection specialists in delegated design situations. They've had a good deal of success with wood to wood moment connections using things like timber rivets and the sexy hardware -- and associated design methods -- coming out of Europe.
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.
RE: Hip Roof
checkinganalyzing a multi-bolt wood moment connection seems like a headache.RE: Hip Roof
RE: Hip Roof
@XR250: I see it and I agree. My faith in it would be, in part, a function of roof pitch. What I'd agree with at 12:12, I might object to at 3:12. For stability stuff, I just prefer a load path that's a little more... discrete. I'll stamp yours if you'll stamp mine.
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.
RE: Hip Roof
RE: Hip Roof
The short ridge does make it unstable in IMO. Something like a steel flitch there that runs down the opposing hips might be viable to give reliable stability. Then, good connection at the 4 corners and tension in the top plate of the wall should do it.
I have used the "bent" steel frame many times and like that idea too. Might be able to use two of them here, one at each end of the ridgeline (or the peaks of the hips).
RE: Hip Roof