ASTM AASHTO Standards technical note provides information about design requirements for thermoplastic structure systems.

Design Requirements for Thermoplastic Structures are: structural design 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

properties.

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. Since the polypropylene and polyethylene, thermoplastic materials now used for subsurface structures are very stable in the stormwater environment; 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

There are two components to ensuring long term performance of any structural product: the product must be designed, tested and manufactured to meet meaningful product standards and the system must be designed to meet meaningful design standards. ASTM and AASHTO, the most respected, dependable standards available, have developed standards for buried structures.

Buried thermoplastic products must be designed for three conditions: short duration live loads under shallow cover, minimum 1-week sustained loads and permanent earth loads. Load duration is a key criterion for the design of thermoplastic structures since the “apparent strength” and stiffness decrease with increasing load duration.

For live load design, the thermoplastic product must be able to withstand the dynamic load from moving vehicles. Live load design is based on short duration loads and short term material properties. Intermediate load design requires the thermoplastic product to withstand 1-week sustained loads from parked oversized loads.

Additional information on dead loads, strain limits, deflection is explained. AASHTO & ASTM standards are defined and explained.