CMU h/r ratio use r-net or r-avg?
CMU h/r ratio use r-net or r-avg?
(OP)
This should be a quick question for the experienced CMU forks.
In ACI 530, par 3.3.4.1.1, to determine the axial strength, we need the h/r ratio. I tho the r should be the r-net, because usually net sectional properties are used for stress/strain computation, while average sectional properties are used for deflection/stiffness computation.
But then in TEK 14-1, the tables for CMU properties, they listed r-average but does not list r-net, which seems to imply you should use r-average in h/r. (They listed A-net, I-net, S-net, but did not list r-net. They listed A-avg, I-avg, S-avg, and r-avg).
Please help me clarify.
Thanks.
In ACI 530, par 3.3.4.1.1, to determine the axial strength, we need the h/r ratio. I tho the r should be the r-net, because usually net sectional properties are used for stress/strain computation, while average sectional properties are used for deflection/stiffness computation.
But then in TEK 14-1, the tables for CMU properties, they listed r-average but does not list r-net, which seems to imply you should use r-average in h/r. (They listed A-net, I-net, S-net, but did not list r-net. They listed A-avg, I-avg, S-avg, and r-avg).
Please help me clarify.
Thanks.






RE: CMU h/r ratio use r-net or r-avg?
RE: CMU h/r ratio use r-net or r-avg?
Finding the actual properties is far easier than requiring a stronger unit despite the low cost of doubling the for a specific project. I have seen an f'm of over 4500 psi as opposed the usually assumed 1900 psi. That also goes a long way to toward a realistic idea of the action of the structure.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.