MASONRY WALL JAMBS
MASONRY WALL JAMBS
(OP)
When designing a masonry wall jamb at a door or window opening can you use the effective width in compression as defined in ACI530 (least of c/c bar spacing, six time wall thickness, or 72”) or should it logically be half that?
Does anyone else find that this tends to be a weak link in a masonry wall system particularly if the openings are large and the walls are tall? I’ve been using concrete columns or 12” thick jambs often on large overhead doors.
Does anyone else find that this tends to be a weak link in a masonry wall system particularly if the openings are large and the walls are tall? I’ve been using concrete columns or 12” thick jambs often on large overhead doors.






RE: MASONRY WALL JAMBS
DaveAtkins
RE: MASONRY WALL JAMBS
All to often the 6t is superceded by tighter reinf. spacing, generally 48" oc, cutting the effective compressive width to 28". It's been difficult to explain to architects that the maximum opening size must be less than the typical bar spacing because of the reduction of nearly half the wall section spanning vertically.
Yeah, I specify to grout and reinf. multiple jamb cores where it works but still have difficulty with large openings.
I should mention that most of my work is in the high wind areas of south florida. We use the hollow precast lintels with notched bearings to allow the reinforcment to pass thru the first core.
RE: MASONRY WALL JAMBS
DaveAtkins
RE: MASONRY WALL JAMBS
The c.c. spacing between bars or 72" should be referring to the maximum effective wall width per bar. That means, the maximum effective flange width for compression corresponding to a bar at yeild, for beam action.
These are two diffent issues.
The effective jamb width should be the BP + 4t. This should be the maximum design width also for bending for wind jamb, unless the jamb as mentioned earlier is broken or discontinuous at the lintel bearing.