In the past, recycled plastic materials had been used for products which were not structural elements, however, in recent years they are being used as structural members due to their cost effectiveness, low maintenance and good buildability. Fibre reinforced plastic (FRP) material has long been available and has been commonly used to construct structural elements overseas for many years. There is currently no Australian Standard for the use of recycled plastic, WPC material or testing of FRP as structural elements. Companies around the world have had the WPC and FRP structural engineering properties established by series of laboratory testing.

 

SIS have commissioned NATA accredited testing to undertake a number of tests using WPC and FRP samples of various sizes, in order to determine the relevant engineering properties of the material for use in design calculations. The testing has generally been undertaken in accordance with the ASTM (American Society for Testing and Materials) International standard test methods for testing of plastics. ASTM International was formally known as ASTM. The European standard EN 13706:2002 Reinforced Plastics Composites- Specifications for Pultruded Profiles  is commonly used for testing FRP material. The testing has established such values as bending, compressive and tensile strengths, Young’s modulus of elasticity, screw pullout capacities and thermal expansion coefficient. Tensile properties from FRP tests can be obtained as per AS 1145:2001 Determination of tensile properties of plastic materials,  which is based on ISO 527.

 

For ultimate and serviceability design loading of structures, AS1170:2002 has been adopted. For boardwalk structures considered to be ‘bridge’ structures, AS5100.2 Bridge Design – Design Loads has been used for the appropriate ultimate design factors.

 

In the absence of specific Australian Standards for the design of WPC material as structural elements, our engineers have opted to follow the ultimate load formulae in AS1720.1 Timber Structures, for bending, compression, deflection and connection design using the material properties determined during testing. Due to the variability of timber as a natural product, the reduction factors built into the strength and deflection calculations in AS1720.1 provides a conservative design result for using the WPC material.