Determination of Tensile Elastic Modulus in High Density Polyethylene Piping at Seismic Strain Rates

For corroded piping in low temperature systems, such as service water systems in nuclear power plants, replacement of carbon steel pipe with High Density Polyethylene pipe is a cost-effective solution. Polyethylene pipe can be installed at much lower labor costs than carbon steel pipe and High Density Polyethylene pipe has a much greater resistance to corrosion. Data was developed by the three testing tasks for use in the seismic design of above ground High Density Polyethylene Piping systems. This paper presents the results of testing to determine the relationship between tensile elastic modulus and strain rates commensurate with seismic loading. This is accomplished by first establishing a seismic strain rate for High Density Polyethlene using detailed finite element analysis. The results of this analysis are used to establish a test matrix tensile testing. Next, tensile tests are conducted using standard ASTM D-638 Type III tensile specimens. The tensile testing is conducted at three pull speeds to establish a basic relationship between tensile elastic modulus and strain rates. This relationship is then used to calculate the modulus at the strain rates expected under seismic loading. This paper presents the results of this testing and the suggested tensile modulus for use in seismic analysis.