APPENDIX B2. Continued - LR-03-190068

LR-03-19
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9.2

9.3

Thermoplastic polymers are known to creep under a sustained stress. Have you

established the creep rate for the final polymer mix that constitutes the material of your

vinyl sheet pile products? If so, what it is.

See attached report from Polymer Diagnostics Inc.

9.4

Impact Resistance:

Have you established any change with time the impact resistance of the material

constituting your vinyl sheet pile products by exposure to out door conditions (sunlight).

If so, what is the rate of change?

See answer to 9.1 above.

10. Any other information you consider pertinent to these studies.

Contrary to popular engineering practice, we feel very strongly that Allowable Moment as

determined by the product of Section Modulus x Design Stress never be used in determining

suitability of a specific section for a given application. This is due to the fact that, to my

knowledge, no wall has ever failed due to exceeding the yield strength of the plastic. Our

feeling is that the modulus of elasticity of vinyl is so low that a vinyl wall will fail due to

unacceptable deflection long before it will fail in yield (see attached Tech Note). As a result,

our published Allowable Moment value is determined by the amount of moment that will

cause approximately 1" of initial deflection and 3" of deflection after 30 years of service.

This is the single largest cause of confusion in the industry. Because of the relatively broad

curve of the stress-strain curve for pvc, you have three different manufacturers calculating

allowable moment using three different design stress values. Quite honestly, we only publish

the value so we can be included on projects where the engineer has used allowable moment

as the design criteria.