Optimization Analysis of Internal Force Data within Piles Based on Concrete Damage Models

The elastic modulus of concrete is one of the critical parameters in calculating the internal forces of pile structures. Due to its inherent complexity and variability, it directly impacts the interpretation accuracy of internal force measurements in piles. This study addresses the issue where significant discrepancies arise between the interpreted internal force data of bored piles and the applied loads at the pile head during static uplift load tests, when a fixed elastic modulus of concrete is used for interpretation. Such discrepancies are inconsistent with fundamental mechanical principles. This paper begins by conducting a detailed analysis of the variation characteristics of sensor data at the calibration cross-section of bored pile internal force measurements. By integrating the static load application conditions and the deformation characteristics of the pile body, a method is developed to inversely determine the elastic modulus and tensile strength of the pile concrete using multi-stage load data. Subsequently, a reinforced concrete damage model based on measured data is established, enabling the interpretation and optimization of internal force measurements in bored piles during static uplift load tests. Case study results demonstrate that the strain variation characteristics at the calibration cross-section during the static uplift load test are closely correlated with the magnitude of the pile head load, reflecting the damage characteristics of the pile concrete. When calculating the elastic modulus of the pile concrete, the inverse analysis of damage model parameters yields results that are more consistent with actual conditions compared to the empirical parameters recommended in design codes, providing axial force calculations that align well with the pile head load. Therefore, the interpretation of internal force measurement results in bored piles during static uplift load tests must fully account for the damage state of the pile concrete.