Connecting a non load bearing masonry partition wall to a wood truss roof system.

[CivilPipe]

We are designing a building which includes a 16’8" tall masonry partition wall with seismic loading. I would like to connect the partition wall to the roof diaphragm with a connection that transfers the out of plane loading from the wall into the diaphragm but detail it such that the diaphragm does not transfer in plane loading into the wall. I have done this before with two steel angles where I need to transfer the loading into a concrete or steel roof system. This building will have a wood truss system with 5/8 inch plywood ceiling and 5/8 inch plywood roof. Can someone point me in the direction of a simple detail for this?
Thanks!

 

[Nor Cal SE]

I would be nervous about any scenario that would put out-of-plane loads directly onto the sides of trusses and force the trusses to resist that out-of-plane bottom-chord load. Two ideas come to mind, but neither is extremely simple:

1) You could bypass trusses altogether and put diagonal braces every 4' or 6' (whether steel or wood) directly from top of CMU wall to roof, transferring load into your roof diaphragm with appropriate blocking/nailing, etc.

2) You could add a series of blocking (again, every 4' or 6') between bottom chords of all trusses, in every single bay in both directions from the CMU wall, until the blocking hits the exterior walls. Then it would be entirely tension/compression of the blocks the entire length, not relying on truss weak-axis bending.

I probably prefer #1 slightly. Admittedly, both are complicated, and others might have better suggestions. I've probably never had a CMU partition wall in a wood-roof building.

 

[CivilPipe]

I am using 5/8-inch plywood ceiling which should do a good job of transferring the load into the roof trusses.
What do you think about using blocking behind the plywood and bolting a steel angles through the blocking on each side of the wall. See attached.

http://files.engineering.com/getfil...-ae69-362b50c68d91&file=20170329092300751.pdf

 

[JGard1985]

I'd be concerned with prying on your bolted angle connection. Is there anyway to dowel the CMU wall into the blocking/plywood above? Maybe let the rebar run long into plywood/blocking above?



Jeff
Pipe Stress Analysis Engineer

http://www.xceed-eng.com

 

[structuralsteelhead]

To confirm. Complete new building? Or alteration to existing? And is the building design engineer regularly engaged in building design? Sorry had to ask before moving forward.

 

[dik]

Just a caution, in some areas due to changes in humidity, there is a feature of trusses called 'truss uplift'. Careful how and where you connect.

Dik

 

[hokie66]

CivilPipe,

I like your detail. Connecting to the ceiling diaphragm is really your only option. If you didn't have a ceiling diaphragm, I would be at a loss for suggestions.

 

[CivilPipe]

structuralsteelhead - This is a new building SDC D - Occupancy Category III

We design many single story masonry buildings with wood truss roof systems. Normally I would stop the partition walls short of the trusses with no connection. I normally check the walls for seismic where applicable assuming a free top and fixed base. This requires vertical steel in the masonry partition to resist moment at the base of the wall as well as designing the slab under the wall to resist the moment. This particular design requires a 16'8" high masonry partition wall. Rather than try to design with a fixed base, I would like to try pinning the top. Can't seem to find any good details for this (easy to construct). Thanks.

 

[structuralsteelhead]

CivilPipe,

Sorry never got back to you last week.

I would tend to agree with Nor Cal SE in regards to getting the lateral force to the typical diaphragm. Why have two diaphragms?,...you'd definitely have some additional redundancy, you'd be repeating all nailing/blocking requirements at the ceiling level at the bottom chord of all joists then and then what at the roof sheathing? Duplicate? Seems like a lot of extra material and labor. Better to keep the better quality construction at the weathering interface above.

If you need the hard top ceiling I would almost still be incline to keep the top chord sheathed and fastened/blocked properly and let the ceiling, which is exposed to the potential of owner modification throughout the unforeseen future not knowing what he/she is doing to a structural element, left to a minimum non-structural fastening schedule.

Maybe a 3x flatwise strongback every 4 ft. across the top of the bottom chords of three or more trusses with kickers in both directions up to some top chord blocking. Drop a couple 2x's, depth to match bottom chords below the strongbacks, with a space for bolting. Kickers detailed similarly to top plate bracing you would place at an gable end wall condition. Truss block or cross brace this group of trusses together at each location. Let the truss designer in on this detail solution as well. Through bolt the sandwiching steel angles to the strong back/double 2x assembly with your required deflection criteria.

Hope this helps,...but maybe for next time due to delay in response.