NONLINEAR PREDICTIONS FOR HDPE PIPE RESPONSE UNDER PARALLEL-PLATE LOADING

Polymer sewer pipe load carrying ability when deflected to 20% pipe de formation under parallel plate loading is used in industry as an index of pipe quality. New developments in limit stares design also require the assessment of pipe response beyond the small deflection limits cu rrently specified (between 5 and 7.5% change in pipe diameter). New ma terial models recently developed to predict the nonlinear time-depende nt response of high density polyethylene (HDPE) are used in a material ly and geometrically nonlinear finite-element analysis to predict pipe response during the flattening test. Comparisons are made with test r esults for two different plain HDPE pipes. The new analysis permits go od quality predictions of pipe response to be made at large deformatio ns (20% vertical diameter decrease) where materially nonlinear polymer response occurs at crown, invert, and springline. Modeling permits pi pe response to be evaluated under a constant rate of deformation, stre ss relaxation, and other load paths.