The final design of reinforced concrete pipe walls is not specified in detail on the plans. The required strength of the concrete pipe is indicated on the plans by the D-load that the pipe will be required to support in the test for acceptance. With this designated loading, the manufacturer can determine the most economical structural design of the pipe walls and reinforcement that comply with the applicable American Society for Testing and Materials (ASTM) specification.

The D-load is written as a number followed by (-D). For example, consider the shorthand notation of 1350-D, which represents 1350 lb./ft. of pipe length per foot of pipe diameter (lb./ft./ft.). For this example, multiply 1350 by the pipe diameter (in ft.) for the total allowable loading per foot of pipe length. (65-D represents 65 N/m of pipe length per millimeter of diameter (N/m/mm). For this example, multiply 65 by the pipe diameter in mm to obtain the total allowable loading per meter of pipe length.)

Design load (D-load) values have been computed for a range of conditions and are tabulated in the document. The D-load values depend primarily on the following:

The soil weight used for preparing the tables is 120 lb./cu.ft. (18,857 kN/m

3

). Live loads are determined using AASHTO methods, and the design loads for the various pipe diameters and corresponding fill heights are based upon the American Concrete Pipe Association Design Manual (Rev. 1978).