SPIDA Method for Reinforced Concrete Pipe Design

Abstract

The required supporting strength of a buried pipe is affected by the total load imposed upon the pipe and the manner in which the pipe is supported by the surrounding soil. The classic procedure for designing reinforced concrete pipe is the indirect design method, which is based on: (1) Determining the moment that will occur at the pipe invert under the specified loading conditions; (2) determining a three‐edge bearing load or D‐load that produces the same moment; and (3) designing the pipe reinforcing for that D‐load. Direct design methods determine the actual moments, thrusts, and shears in the entire buried pipe and they design the reinforcing to carry these forces. The advent of finite element modeling of soil behavior now allows an even more direct design method in which the actual soil conditions around a pipe are accurately modeled. This paper will demonstrate the differences between the various design methods by analyzing an actual installation with both methods. The finite element analyses are completed with the computer program SPIDA (Soil Pipe Interaction Design and Analysis).