Back analysis of tensile test drilled shafts and barrettes

Abstract

This paper presents a method to interpret the tensile test results for a concrete pile when the concrete is stressed beyond its tensile limit, which results in anomalies in the strain gage data that is collected during active load testing. Two drilled shafts and two barrettes are studied using the proposed method. Any pile loads that are computed using strain data and which are greater than the specific applied load are discarded because these results are physically impossible. A Spline function is then used to fit the remaining valid data for pile load along the depth. Using the fitted Spline function and assuming that the behavior at the pile/soil interface can be modeled as a hyperbolic model, a back-analysis method is used to determine the parameters for the model. The software, SHAFT is used to compare the results for the back analysis and the measured gage data. It is found that the back-analysis method that is used in this study gives a reasonable interpretation of the pile loading test results, such as the t-z curves, using the pile force and a depth fitting function.