Supporting truss with beam and hanger

[Said the Sky]

Hello,

client requests that the door be raised up to underside of wall top plate and hence we cannot have a header between the top plate and top of door,

the truss is cantilevered quite a big distance past the door, looks to be about 6ft (is this normal?)

proposed solution with beam and hanger in attached pictures,

I'll provide straps from top of beam to web for bracing but I've analyzed the beam to span support to support without any top chord bracing at all (Lu for top and bottom chords is full span)

I'll check the bottom 2x4 chord for bending due to the hanger being slighly offset from the vertical web truss member.

looking for critque of this detail and anything to look out for

TIA

 

[Said the Sky]

another picture

 

[Said the Sky]

plan view of area

added beam spans about 15ft, picking up about 4 trusses that runs above the door.

 

[driftLimiter]

Is the truss new or existing? New truss can be designed for this condition might alleviate some concerns. Existing truss....

I would be worried about the bottom chord in shear/bending for one thing. Can you get the hanger to be where the web comes down? Best when working with existing trusses to keep the bearing in the same locations where possible. You could consider adding a web

I don't see any reason why the truss cant cantilever past this door 6ft, seems normal to me.

I'm hoping that your new header is going to be locked into a wall at least at it's ends. There are some straps or other hardware that you can use to provide torsional restraint to the header ends if needed.

Biggest concern is just that little bottom chord pretty much like your thinking.

 

[Said the Sky]

thanks, it is existing trusses, owner wants super high doors.

I have to estimate the loading, I've estimated each truss has a vertical reaction factored load of 1.2kips, and it is offset from the web by about the width of the hanger, I guess I need to size the width of the hanger requirement based on bearing of the bottom chord on the hanger, then use that as my offset distance to calculate bending and shear of the bottom chord.

I tried asking to add a HSS tube steel (4x4 or 5x5 should work) for header just to span the width of the door, but they MUST have the full height door...

 

[phamENG]

they MUST have the full height door...

No, they WANT a full height door. They MUST have a safe and reliable way to walk into their house. Don't go overboard, but don't loose sleep over what you come up with either. If they want this, they have to pay for what it costs to make it happen. If that's replacing 3 roof trusses or significantly re-working them to make it happen...so be it.

To keep bearing for the truss where it is (which I would strongly recommend), you'll be putting a fair amount of torsion on your header. One: how will your header resist that? Two: How will your end connections resist that? You'll probably end up with a steel tube above the bottom chord with a custom fabricated bracket at each truss. Your connection to the outer walls will be thick steel plates that can break your torsion down into a tension load (transferred into the wall somehow - probably need to add a stud or two with a hold down) and compression through bearing.

 

[rb1957]

what if you gave them a false ceiling, 4" lower ? I assume there is a roof over the verandah ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[KootK]

...looking for critque of this detail and anything to look out for

1) On balance, I think that your proposed solution is very clever. Naturally, I can do it a bit better.

2) Your original solution does introduce a big shear in to the bottom chord as others have mentioned. Luckily, this is a pretty easy thing to evaluate. It won't have much of an impact on chord flexure or the plate connection which is helpful.

3) If you adjusted your detail as shown below -- and the number checked out -- I feel that you'd be off to the races.

 

[Said the Sky]

thanks all for all your comments

I've drawn out hte details before I read some of your comments, I like your idea kootk (as always.... you know what to do..)

I'll post my details for you guys if your curious but I might incorporate kootk's detail into mine after I think about it some more....

 

[Said the Sky]

det 2

 

[Said the Sky]

det3

 

[KootK]

I'm not sure how difficult it will be to get the beam up into that space. You might consider planning to cut and field splice the cantilever bottom chords. That shouldn't be a big deal.