Performance Assessment of Wave Equation Analysis for Driven Steel H-Piles in IGM-Article

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The study evaluates the Wave Equation Analysis Program (WEAP) for estimating the resistance of driven steel H-piles in intermediate geomaterials (IGMs), whose properties fall between those of soil and rock and are difficult to represent with standard WEAP inputs.<br /><br />Researchers analyzed 26 H-piles from Wyoming projects, comparing WEAP bearing-graph resistance estimates with capacities measured using CAPWAP. They assessed two toe-quake approaches: WEAP’s default values, and user-defined values of pile dimension divided by 120 (D/120) for IGM-soils and 1 mm for IGM-rocks. Because WEAP does not model IGMs directly, the materials were entered using soil-based parameters and procedures.<br /><br />The default toe-quake approach produced a mean resistance bias of 1.07 and a coefficient of variation (COV) of 30%; the user-defined approach brought the mean bias to 1.00, with the same variability. Overall, WEAP estimates were generally close to CAPWAP results, though some piles were substantially over- or underestimated. The authors conclude that WEAP bearing-graph analysis can be a useful construction-control method for verifying pile capacity in IGMs.<br /><br />Using a preliminary First Order Second Moment calibration, the study recommends resistance factors of 0.58 and 0.55 for the two approaches at a target reliability index of 2.33—both above the AASHTO value of 0.50. These factors are preliminary: they are based on a limited dataset and require validation using more rigorous reliability methods and additional pile cases.

Keywords

Wave Equation Analysis Program

WEAP

CAPWAP

steel H-piles

intermediate geomaterials

pile resistance

toe-quake

bearing graph analysis

AASHTO resistance factor

pile capacity