In North America, close-fitting structural pipe liners are designed according to the American Society for Testing and Materials (ASTM) F1216 design appendix. This design standard is based on the structural buckling theory. A long-term material elastic modulus is introduced to accommodate for material creep for a long-term design. This paper discusses the theoretical incorrectness of applying a long-term elastic modulus in the instantaneous buckling equation, and the technical difficulties in determining the value of the modulus. Based on the critical buckling strain theory introduced in the 1960’s, the authors propose an alternative liner design method. In the proposed design method, the instantaneous buckling equation is used for short-term liner buckling design, then the creep strain and the critical buckling strain theory are used to validate the long-term design.
Compared with the current design method, the proposed design method:
1) is theoretically sound,
2) utilizes mature creep theory and simple creep tests to predict liner long-term performance, and
3) overcomes the over-conservativeness in the current design method.
A design example is given to illustrate the proposed design procedure. Discussions are presented to address some key issues in current plastic liner design, tests, and long-term performance.