The project final report is available as NCHRP Report 631.
The "Soil-Thermoplastic Pipe Interaction System" design procedure (Section 18 and LRFD Section 12) of the AASHTO Bridge Specifications was written in the early 1980s based on the corrugated metal pipe design procedure. This procedure relies on ring compression limits even though this mode of failure may not occur in practice or in research. At the same time, the procedure ignores other relevant performance limits, such as deflection and wall profile stability, and the time-dependent nature of thermoplastic materials is largely ignored. In many cases, these factors limit the cost-effective application of thermoplastic drainage pipe. In other instances, designs may not be conservative or may be susceptible to unexpected failure modes. With more than 40 states currently using some type of thermoplastic drainage pipe, and with large-diameter thermoplastic drainage pipes readily available, this research was conducted to develop a recommended load and resistance factor design (LRFD) specification for thermoplastic pipe for culverts and drainage systems for consideration by AASHTO as well as a QA procedure for manufactured thermoplastic pipe.
