Non-Linear Pile Rigidity Determined from Embedded Stressmeters in Instrumented Bi-Directional Static Load Test Piles-Video

Video Transcription

Video Summary

The presentation examines how to interpret strain measurements from bidirectional static load tests on grouted auger-cast piles and convert them into internal forces. This calculation depends on uncertain inputs, especially grout modulus and pile cross-sectional area. The commonly used ACI modulus correlation can produce unrealistic force profiles, while the incremental rigidity method also has limitations. A piecewise-linear approach offers an alternative, accounting for changes from steel-only to composite behavior as grout stress increases.<br /><br />A case study used concrete stress meters alongside strain gauges in two 36-inch piles. The meters measured the grout’s in-situ stress–strain response, revealing behavior consistent with the piecewise-linear model. Using this model and the stress-meter data produced internal-force profiles that aligned with expected geotechnical resistance; the ACI method did not. The speaker recommends combining stress meters with strain gauges and applying engineering judgment, while noting that further research is needed to refine instrumentation and validate modulus estimates.

Keywords

grouted auger-cast piles

strain measurements

internal forces

piecewise-linear model

grout modulus