This StormTech Structural Design technical note explains Thermoplastic design requirements, structural design and analysis of standards. Table and detail provided.

This Technical Note summarizes key components of structural design and national standards for subsurface thermoplastic structures. The purpose is to provide a single point of reference for North American structural design principles and a cross-reference to Eurocode structural design methodology. Although the focus of this guidance is on arch-shaped chamber systems, the principles apply to the wider category of buried products of various structural shapes and material properties.

Design requirements for thermoplastic structures must evaluate short-term live loads, intermediate-term loads and long-term soil loads. The materials used in production must provide necessary short-, intermediate- and long-term mechanical properties. The structural design must be completed by experts in the field of soil-structure interaction. The product must be designed and manufactured to meet meaningful standards and the structural design of the subsurface stormwater system must be up to the standards that a professional engineer expects from short-, intermediate- and long-term soil loads.

The objective of structural design is to ensure a proper safety factor over the intended service life of the buried system. Typically, the intended service life of a subsurface storm drainage system ranges from 20 to 100 years. The polypropylene and polyethylene thermoplastic materials used for subsurface structures are very stable. The limiting criterion for service life is generally long-term structural stability. The primary benefit of subsurface systems is to facilitate additional paved surfaces for the purpose of parking or traffic flow. For a design to be safe, structural safety factors must be demonstrated for the entire service life of the project to account for uncertainties in loading, installation and material performance.

North American structural design approach with short-term, intermediate and long-term property’s strain and deflection discussed. AASHTO and ASTM standards listed with linking them to Eurocodes. Eurocode modelling study with cover per chamber table included.

Load cases and analysis with results are explained. CANDE FEA detail provided.