Brick Bearing Pressure
Brick Bearing Pressure
(OP)
What would be an appropriate allowable bearing pressure for brick masonry? Not finding anything in the ACI 530, but I don't think it's really applicable as this not a recent building.
Looking at a bearing plate on a 12" thick wall of 3 wythes of 4' brick.
Looking at a bearing plate on a 12" thick wall of 3 wythes of 4' brick.






RE: Brick Bearing Pressure
RE: Brick Bearing Pressure
Thanks
RE: Brick Bearing Pressure
RE: Brick Bearing Pressure
A 1982 Navy manual uses quite high bearing values based on .25 f'm but they assume that the bricks have a unit compressive strength of 8000 psi. Although the building looks good, that sounds pretty high based on concrete test results that we get nowadays, so I am not going there.
Other much earlier references show a bearing ranging from 100 psi to 400 psi depending on brick compressive strength and mortar type.
At 100 psi, the bearing plates will be unmanagable.
RE: Brick Bearing Pressure
Check out the Brick Industry Association www.bia.org
They have many technical reports available online at the following link:
http://www.bia.org/html/frmset_thnt.htm
You can scroll through them on the left side of the page. This is taken from Tech. note 17b:
"The designer should check the stress condition at bearing points for RBM beams. This applies to loads on the beam and to the beam's reaction on the wall. The MSJC Code limits the bearing stress to 0.25 f'm, where f'm is the specified compressive strength of masonry. A rule-of-thumb recommended for many years is to provide a minimum of 4 in. (100 mm) of bearing length for masonry beams. The masonry directly beneath a bearing point should be constructed with solid brick or with solidly grouted hollow brick. Concentrated loads should not bear directly on ungrouted hollow brick masonry because of the potential for localized cracking or crushing of the face shells."
If you feel better using 100 or 200 psi or something like that by all means do so. This site along with the ACI suggests that 0.25f'm is sufficient. In other technical notes on that page - such as the material properties one - the compressive strength of some of the brick them sleves exceeds 10000 psi. To me, that means assuming 1500 psi should be sufficient, giving you a bearing stress of 375 psi. 200 or 300 would be good too, and definitely better than 100 psi.
RE: Brick Bearing Pressure
RE: Brick Bearing Pressure
DaveAtkins
RE: Brick Bearing Pressure
Any chance of testing some of the brick?
Bricks expand with age as they draw in water. Yesterdays bricks were not necessarily made like today's bricks.
I am assuming no design data is available on the building or similar ones in the area?
Good luck
daniel
RE: Brick Bearing Pressure
It's an oldie, but it really doesn't look bad.