Shortening A Tall Masonry Wall

[ctm]

Can I insert an intermediate poured concrete bond beam at the mid height of an exterior reinforced concrete masonry block wall and proceed to design the wall for lateral wind, not axial gravity, as two walls of height h/2 each? I would use different axial loads on each and would use the unity equation for axial and bending.

Please assume that the wall is carrying a concentric axial gravity load and a perpendicular lateral wind load.

Please also assume the bond beam is properly reinforced and terminates at a perpendicular shear wall on either end.

 

[dik]

Not unless the bond beam is secured against lateral movement, if I understand you correctly.

 

[phuduhudu]

ctm,

Do you mean the beam runs along the length of the wall? If you can do that so that the top half of the wall is entirely supported by the beam and the beam can take the loads back to the supports then it can work. You also need to laterally restrain the bottom half of the wall at the top (without attracting additional vertical load). There are standard details for this kind of thing where you have infill panels in a concrete frame for instance. If you can do all this then you can design it as you suggest. Although removing the vertical load from the bottom half of the wall will not help in dealing with the lateral loads. Why are you doing this? Carl Bauer

http://www.bauerconsultbotswana.com

 

[ctm]

dik,

I was hoping to treat the reinforcing in the bond beam and the shear wall end anchorages as security against lateral movement.

carlbauer,

The beam does run along the length of the wall.

I was doing this to make a wall more contractor friendly without changing any of the wall externals thus architect friendly.

Recently encountered a wall a bit less than 30 feet high in a 110 MPH coastal wind zone that had to be 12 inches thick with 8 to 16 inches spaced #6 vertical rods.

Can either of you suggest an idea; if nothing comes to mind, so be it.

Thank you both for your replys.

 

[dik]

Carl:
I've no idea of how close the vertical elements are, but if the ends of the bond beam are close enough to be of use, then lateral support of the wall is likely moot...

Unless bond beams are braced (and could be by relatively close vertical elements) I usually don't consider these as points of lateral support. I prefer to treat masonry as a flexural element, not a membrane.