The Portland Cement Association (PC

The Portland Cement Association (PCA) has publications for designing rectangular and circular tanks. Some of the design provisions differ from that of the American Concrete Institute (ACI) specifications. Many in the industry use these PCA design concepts, so we will adapt them for our calculations as well. Much of the PCA publication is comprised of tables of coefficients for calculating moment and shear in two-way slabs. These tables should simplify the calculations. We will refer to the PCA Rectangular Concrete Tanks design manual as PCA-R, and the circular tank design manual as PCA-C.
An additional safety factor is used for the loads called the “Sanitation Coefficient”, we will denote it with SC for brevity. Note that this notation is not an industry standard. The purpose of the sanitation coefficient is to indirectly reduce the stress, and thus the strain, in the steel reinforcing. The result is lower strain in the concrete, and thus less cracking. The ultimate load will be multiplied by SC, which has different values for different calculations:
1.3 for flexure
SC= 1.65 for direct tension (hoop tensile stress in reinforcing)
1.0 shear provided by concrete
1.3 for shear beyond that provided by concrete
Another change is the fluid load factor is 1.7 rather than 1.4 as stated in the ACI specification. For the purposes of this class, the following load combinations and factors will be used:
Mu = 1.3(1.4D + 1.7F + 1.6H) for flexure
Pu = 1.65(1.4D + 1.7F + 1.6H) for direct tension (hoop tensile stress in reinforcing)
Pu = 1.0(1.4D + 1.7F + 1.6H) for direct compression (hoop compression stress in concrete)
Vu = 1.0(1.4D + 1.7F + 1.6H) shear provided by concrete
Vu = 1.3(1.4D + 1.7F + 1.6H) for shear beyond that provided by concrete
D = dead load F = fluid pressure H = earth pressure