Deck joists attached to floor joists 1

[buleeek2]

Hello everyone,

Every once in a while I need to design a deck with joists fastened to the side of floor framing. See attached. I am wondering what your approach would be to come up with shear forces in bolts B1, B2, and B3.
See attached and thank you for your input.

 

[buleeek2]

ENG16080,

Double channels connection is not the worst idea, thanks.

Conservatively assumed a person standing at the tip. Otherwise, there is only dead + snow (balanced + drift).

XR250,

As I said, I modeled it as each bolt is a spring support.


Thank you,

 

[phamENG]

I don't like this at all, but you seem undeterred. At least use full height sheathing in conjunction with the packing so you can actually engage the full section without relying a little glue between the web and the chords. It works well enough for shear flow, but concentrated loads? Not as much.

 

[Celt83]

"I modeled the bolts as spring supports (100 lbs capacity / (1/16" deflection) = 19.2 k/ft)"

The vertical spring of the bolts is going to be tied to the vertical deflection of the joists, which is just going to make the bolt nearest the exterior wall have the most stiffness. Distributed bolts is not the way to go for something like this in my opinion.

I would likely bear the steel beam on the wall and give it a healthy back span to an LVL blocking beam between the joists and fasten to that.

 

[buleeek2]

Celt83,
That sounds like a good idea. Would you attach the new beam to adjacent TJIs with top flange hangers?

 

[Celt83]

Personally I don’t prefer the channel suggestion as it complicates the waterproofing installation at the envelope, tube gives 4 flat surfaces to flash against and the natural deformation tendency would send water to the exterior tip. I would give consideration to installing on a slight slope and adding a weep hole to bottom of the tube at the exterior to deal with any condensation that may form from difference in environments across the tube.

 

[phamENG]

If doing the tube with bolts, I'd oversize the hole on the side not in contact with the joist so the head of the bolt can fit through and bear against the inside face of the other side.

 

[Celt83]

Celt83,
That sounds like a good idea. Would you attach the new beam to adjacent TJIs with top flange hangers?

Believe you said the I-joists are existing if so I'd avoid top flange hangers, you'll need to look at your loads as I imagine with a lightly loaded canopy you might end up with wind uplift being a design consideration which would change the back span reaction direction.

I'd look at packing out the joist web on both sides, some form of full depth cap piece either 2x or plywood, dependent on load magnitudes maybe an inverted face mount hanger to deal with uplift reactions combined with A35 or sim clips to deal with downward reaction. I'd look at bolting the steel beam to the LVL blocking beam with angles.

 

[Eng16080]

Double channels connection is not the worst idea

Thank you. I will take the compliment.

Conservatively assumed a person standing at the tip. Otherwise, there is only dead + snow (balanced + drift).

Ok, so this is a roof then, and not a deck which would be supporting people (live load of 60 psf)? I was thinking the latter, which was why the loads seemed low to me.

If doing the tube with bolts, I'd oversize the hole on the side not in contact with the joist so the head of the bolt can fit through and bear against the inside face of the other side.

I'll second this if going with the tube option.

Personally I don’t prefer the channel suggestion as it complicates the waterproofing installation at the envelope

True, but I would still prefer channels due to them not trapping moisture like an HSS could.

 

[SWComposites]

If doing the tube with bolts, I'd oversize the hole on the side not in contact with the joist so the head of the bolt can fit through and bear against the inside face of the other side.

Agree 100%. Bolting thru a hollow section is likely to not result in much if any clamp-up of the tube wall to the joists (unless you somehow insert blocks into the tube). And not having clamp-up is very bad for bolted joint strength. And oversize the outer tube wall holes on both sides to allow for bolt heads, washers, nuts and sockets to fit thru.

 

[milkshakelake]

Can you add a hanger or kicker to that canopy? The cantilever span is large.