The Influence of RC Nonlinearity on p-y Curves for CIDH Bridge Piers-Article

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The study examines whether nonlinear shear deformation should be included when deriving and applying p-y curves for reinforced-concrete cast-in-drilled-hole (CIDH) bridge piles. Conventional p-y analyses commonly account for nonlinear flexure but neglect shear, an assumption that may be unsuitable for piles with rotation-restrained, fixed-head conditions.<br /><br />Researchers modeled two 0.61 m-diameter piles in OpenSees: a free-head “flagpole” pile and a fixed-head pile. Both models included nonlinear flexure; one also incorporated shear–flexure interaction. The soil response was represented by experimentally derived p-y curves, and model predictions were compared with large-scale test results.<br /><br />For the flagpole pile, shear forces and deformations were small: shear contributed less than 1% of peak lateral displacement. The response was primarily flexural. In contrast, shear significantly affected the fixed-head pile’s behavior. Shear deformation accounted for as much as 30–40% of total lateral displacement, and the coupled model predicted roughly 10% lower maximum lateral load than the flexure-only model. Importantly, shear effects emerged before the pile reached its nominal shear capacity.<br /><br />The results indicate that p-y curves calibrated using flexure-only models may underestimate lateral displacements and may lead to unconservative designs for fixed-head or similar piles. The authors recommend accounting for nonlinear shear deformation in these conditions and propose additional sensor-based testing to validate the findings and recalibrate p-y curves.

Keywords

p-y curves

shear deformation

reinforced-concrete piles

CIDH bridge piles

fixed-head piles

flexure-shear interaction

OpenSees modeling

lateral load response

nonlinear analysis

soil-structure interaction