Wood Joist Connection to LVLs 8

[Vrpps EIT]

Hi,
Can a 12" Joists be connected to the bottom half of a 3x24" deep LVL 2.0E wood beam via face mount hangers. The LVLs are connected to wood columns studs. Will this connection withstand an overturning effect? as the LVL is loaded on only one side with a 4' parapet wall attached on top of it. The span & loadings are attached in the drawing.

 

[Triangled]

your compression edge of beam is unsupported.

 

[XR250]

Looks sketchy to me. Also, how is the wind load on the parapet resisted?

 

[JAE]

What resists the lateral wind load on the parapet? I don't see any legitimate load path there.

The gravity connection of the hangers to the LVL is fine.

But you need to deal with twisting of the LVL from the parapet and from the eccentric joist load.
Many face mount hangers have no qualified lateral connection capacity or moment resisting capacity.

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[Agent666]

Any reason why you can't drive some long screws from the outside face into selected joists to resolve the moment? I'd agree with the others that the joist hangers certainly seems a little weak for resisting the moment as they are usually very thin plate.

Our local non specific engineering code (can use with no engineering input) has a similar detail for handrails/barriers for safety from falling, it calls for 2 x M12 x 250mm long coach screws to be driven through the supporting member into the joists and also metal straps top and bottom to deal with the moment transfer, perhaps you could use/adapt something similar if the numbers work out.

 

[hokie66]

I would look at a cant above the joists to brace both the parapet and the LVL beam. You need a cant in the roofing anyway, that just gives you a decent size one.

 

[JoshPlumSE]

How does the moment get into the LVL? Then how does it go from the LVL into the joist?

I might run the parapet full height past the LVL and then add a strap from the Joist to the bottom of the LVL / parapet. That's one half of the force couple needed to transfer the moment. Then I'd add something to the top of the LVL as well maybe a Simpson H2.5. But, then we still need to tie the top of the LVL into the joist or else we're putting a significant torsion on the LVL.

 

[KootK]

Kinda looks like your parapet will be loading you LVL in cross grain bending no matter what you do with this.

Our local non specific engineering code

Looks like a respectable document. Can you share the title?


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.

 

[hokie66]

Agree with Josh that the parapet framing should be on the outside of the LVL. Then add my cant, appropriately screwed to the joists and LVL. Problem solved.

 

[Agent666]

KootK, its NZS3604:2011 Timber Framed Buildings

Theres a freely available handbook for use on site by builders/site engineers which contains selected excepts from the standard.

 

[Vrpps EIT]

To resist the wind load on parapet wall I 've attached a dense sheathing connected to the LVL and then have connected that sheathing to the 2x4 studs of the parapet wall. Hope this will work for the lateral load. To avoid the twisting of LVL, I am thinking of connecting the 12" joists to the top of LVL with a simpson H2.5 tie. Will this connection work guys?

 

[KootK]

Thanks Agent666. I'm glad that I asked. Most countries have a version of that document but the NZ version is the most comprehensive that I've seen so far. Full of candy I can use on future projects...

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.

 

[hokie66]

Veerapps,
The sheathing on the left side of that parapet is not doing much for wind loading.

That cant is not what I had in mind. Think a 2x12, ripped on each edge at 1/1, running parallel to the parapet, screwed to both the LVL and the roof joists.

How does that higher roof figure in? Does it connect to the parapet?

 

[Vrpps EIT]

hokie66,

The higher roof is not connected to the parapet, its a new addition and those 11-7/8" roof joists rests on walls at the front and back. To the left side of the LVL is a 8' ceiling(existing building) and the right side (high roof joist - new building) is a 10' foot ceiling, so I need to tie the existing 8' foot ceiling joists to some support and then my new 10-foot ceiling starts.

 

[Agent666]

Kootk, this might also be of interest. Engineering basis of NZS3604

 

[Vrpps EIT]

well in the case to brace the compression flange, I guess I need to bring down the LVL 1' down and connect the 12" joists on top of LVL via top mount hangers. Hope in this way the buckling could be avoided and the end of LVL's could be connected to wood posts via column cap to prevent the rotation.

 

[Vrpps EIT]

wont a 2x top plate prevent the bowing out of beam?

 

[KootK]

Kootk, this might also be of interest.

Oh yes. Like Christmas in August.

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.

 

[Triangled]

dropping in on this again, an i apologize for not studying the comments of my betters above, but, based upon your last detail 18:52
1. looks kinda like an architectural detail, not structural, and if structural details dealt with elsewhere in your plans, hey, that's great.
2. a 25' span beam supporting unknown length roof joists can carry a big load with a significant reduction in capacity if not braced properly. As it is, I don';t think it is braced adequately, but you're close.
3. i'd extend roof sheathing 100% over the 3-ply beam and be nailed down to it, not stop short at face of dbl bottom plate
4. guessing the horizontal lines below the IJoists represents drywall and not plywood, this drywall is of no value to resist buckling of 3-ply beam
5. therefore when 3-ply beam tries to buckle out of plane towards the IJoists, the mechanism(s) resisting this movement is , nails thru nailed down edge of roof sheathing + nailes down thru top flange of hanger and that connection to the 2x12 joists - which connection I'd bet the connector fabricator did not envision for that hanger.
6. also when 3-ply beam tries to buckle out of plane towards the IJoists, the plies may want to separate, especially if the left ply is held in place somewhat by the hanger and the right ply is not - this mechanism will strain your fastening system between your three plies - all that to say, I would not rely upon nails to fasten together your 3 plies in this case (although i may in other cases), but, in this case i'd consider bolting with washers under nut and bolt-head, at the least, screws.
7. consider using a simpson hurricane tie that nails to side of 2x12 joists goes up and over the 3-ply beam and bends down the right side, all nailed off.
8. Your parapet is not laterally braced, but has a 'hinge' at the bottom. you can easily connect the parapet studs at the top of the IJoist level with blocking and connectors.

 

[Vrpps EIT]

thank you very much Triangled! for the detailed explanation, you made my day!