Helical Pile Hyperbolic Load Deflection Analysis-PPT Presentation

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This study evaluates a hyperbolic method for predicting the load–deflection behavior of helical piles, an area with less established guidance than axial capacity prediction. Earlier research offered a four-point method for constructing load–deflection curves, but comparisons found agreement in only 55 of 353 test graphs (15.6%). That method performed best in clay.<br /><br />The researchers analyzed 353 AC358 certification tests supplied by CTL Thompson: 179 compression tests and 174 tension tests from eight manufacturers. The measured load–deflection curves generally resembled rectangular hyperbolas. The study linearized the hyperbolic relationship by plotting deflection/load against deflection, allowing two parameters to describe each curve: an initial stiffness and an ultimate-load asymptote.<br /><br />The asymptote, represented by 1/b, showed a substantial relationship with predicted ultimate pile capacity: 1/b = 1.5487 times predicted capacity, with R = 0.8214. By contrast, the initial stiffness, 1/a, was only weakly related to calculated pile-shaft stiffness (1/a = 0.3658 times shaft stiffness; R = 0.2183).<br /><br />The results suggest that hyperbolic analysis may provide a useful way to characterize helical-pile load–deflection behavior and estimate ultimate capacity from test data. However, the weak relationship between initial stiffness and shaft stiffness indicates that further work is needed to predict early-stage deflection reliably.

Keywords

helical piles

load-deflection behavior

hyperbolic method

ultimate capacity

AC358 certification tests

deflection/load linearization

initial stiffness

rectangular hyperbola

compression and tension tests

pile-shaft stiffness