Nonlinear Predictions for HDPE Pipe Response under Parallel Plate Loading

Abstract

Polymer sewer pipe load carrying ability when deflected to 20% pipe deformation under parallel plate loading is used in industry as an index of pipe quality. New developments in limit states design also require the assessment of pipe response beyond the small deflection limits currently specified (between 5 and 7.5% change in pipe diameter). New material models recently developed to predict the nonlinear time-dependent response of high density polyethylene (HDPE) are used in a materially and geometrically nonlinear finite-element analysis to predict pipe response during the flattening test. Comparisons are made with test results for two different plain HDPE pipes. The new analysis permits good quality predictions of pipe response to be made at large deformations (20% vertical diameter decrease) where materially nonlinear polymer response occurs at crown, invert, and springline. Modeling permits pipe response to be evaluated under a constant rate of deformation, stress relaxation, and other load paths.