Uplift on masonry wall
Uplift on masonry wall
(OP)
I have a general question about uplift on a fully grouted masonry wall. I am looking at FEMA 361, Second Edition / August 2008, page 6-26 (166 of 374) Figure 6-4. Here is a dropbox link to that page:
https://www.dropbox.com/s/5zjiqca8qo8v1it/FEMA%203...
This is a diagram showing continuous load path from roof to foundation. See position 3 in the diagram. It shows a steel roof beam bearing on an embed plate with hooked anchor bolt(s) into a masonry bond beam. It also shows vertical reinforcing extending into the bond beam.
Question: Would you consider this an interruption in the continuous load path? It seems to me that the vertical reinforcing would have to develop past the embed plate.
Secondary Question: If you agree that the vertical bar should develop past the embed plate, would you consider the point of beginning for the development length, the top of the hook of the hooked anchor bolt or the bottom of the embed plate?
My concern is that during the tornado the roof and single course bond would detach from the rest of the wall failing the storm shelter.
https://www.dropbox.com/s/5zjiqca8qo8v1it/FEMA%203...
This is a diagram showing continuous load path from roof to foundation. See position 3 in the diagram. It shows a steel roof beam bearing on an embed plate with hooked anchor bolt(s) into a masonry bond beam. It also shows vertical reinforcing extending into the bond beam.
Question: Would you consider this an interruption in the continuous load path? It seems to me that the vertical reinforcing would have to develop past the embed plate.
Secondary Question: If you agree that the vertical bar should develop past the embed plate, would you consider the point of beginning for the development length, the top of the hook of the hooked anchor bolt or the bottom of the embed plate?
My concern is that during the tornado the roof and single course bond would detach from the rest of the wall failing the storm shelter.






RE: Uplift on masonry wall
RE: Uplift on masonry wall
RE: Uplift on masonry wall
Alternatively, you could try a precast system (hollow core planks or double tees) with a topping slab. Construction is quick and simple and the detailing isn't too bad.
RE: Uplift on masonry wall
1) If you think that you'll reliably have vertical bars right under the embed plate, then you would develop the bars beyond the point where they intersect the pullout cone for the anchor bolts. This would be very similar to how you would normally deal with anchors and pier reinforcing at a column base plate connection in tension.
2) You can anchor the bolts to the bond beam, transfer the tension along the length of the bond beam to where there are vertical wall bars, and then anchor those vertical bars into the bond beam from below. This seems to be what the FEMA document is suggesting. Trouble is, it's really an anchorage problem rather than a development problem and I don't really know how to assess that in a masonry/rebar connection.
I'd like to use a two course bond beam and use embedded deformed bar anchors on the bearing plate to get a more convincing "lap" with the adjacent vertical bars. That might be tough to sell to your contractor, however, as it will tend to look unconventional.
FEMA really doesn't mess around with spelling out the load path continuity thing, do they?
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.