Three-wyth, unreinforced, freestanding wall
Three-wyth, unreinforced, freestanding wall
(OP)
I have a client who is dealing with an existing mechanical enclosure without a roof constructed of three-wythe masonry. His client wants to punch 4' wide x 28" tall holes near the bottom of this wall for additional ventilation. Building is only 5 years old, but there are no drawings for this enclosure, and apparently ties have been cut between the owner and the architect...
One exploratory opening was made to determine the construction. Outer wythes are 4" utility size brick. Inner wythe is 4" CMU. No grout between wythes. No 4 dowels 16" long, 24" on center. 9 gage ladder reinforcement at 16" on center vertically. No other reinforcement.
Is there a way to reinforce and grout the collar joints after the fact? How much room do you need to grout? Is it possible to reinforce the 4" cmu?
Thanks,
One exploratory opening was made to determine the construction. Outer wythes are 4" utility size brick. Inner wythe is 4" CMU. No grout between wythes. No 4 dowels 16" long, 24" on center. 9 gage ladder reinforcement at 16" on center vertically. No other reinforcement.
Is there a way to reinforce and grout the collar joints after the fact? How much room do you need to grout? Is it possible to reinforce the 4" cmu?
Thanks,






RE: Three-wyth, unreinforced, freestanding wall
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Three-wyth, unreinforced, freestanding wall
RE: Three-wyth, unreinforced, freestanding wall
Is it a brick-CMU-brick wall configuration? If so, how wide are the areas for possible grouting? - 4" CMUs cannot the filled with grout from a practical standpoint the they are commonly filled with mortar if the dowels are somehow connected to the other vertical steel.
If it is what I imagine the voids between the brick and CMUs are not adequate for grouting according to codes, but there are alternate non-complying methods that will increase the lateral strength
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Three-wyth, unreinforced, freestanding wall
RE: Three-wyth, unreinforced, freestanding wall
The dimensions of the enclosure are 20'4" x 30'-6".
I tried to check the wall spanning horizontally. The shorter wall worked this way if it was fully composite, but I cannot confirm that the void is packed with mortar or grout. The long wall does not check out even if it is fully composite. I didn't really get into checking with the wire joint reinforcement to help with that yet.
We floated the ideas of simply adding roof joists to restrain movement at the top of the wall (this is a 3-sided enclosure with the 4th side being a school building), but the owner didn't like that. At this point I might be running some sort of vertical steel (either internal or external) to add moment capacity to this cantilever wall...
RE: Three-wyth, unreinforced, freestanding wall
Since the owner wants the holes and will not accept and open joist without a roof surface throw the concept of providing vertical reinforcement on the unexposed side, it does not sound like the owner realizes a roof surface over the joists is needed, since he is apparently interested in increasing circulation.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Three-wyth, unreinforced, freestanding wall