Bearing behavior of large-diameter variable cross-section steel composite pile based on optical fiber monitoring

To study the bearing behavior of super-long and large-diameter variable cross-section steel composite pile, a bearing capacity test was carried out on NO.45 pile of Yushan bridge with load produced by the gravity of the pier and the box beam. The behavior of the pile was monitored by distributed optical fiber. The actual working condition was simulated using ABAQUS. The numerical simulation results were compared with the measured data to verify the rationality of the modeling parameters. Based on the finite element model, complex loads of compression load, bending moment, shear force and torque were applied and the parameters of the pile itself were changed to study the influence of pile parameters on the bearing behavior of the pile foundation. The results show that optical fiber monitoring can be well applied to the monitoring of super-long and large-diameter variable cross-section steel composite pile in marine environment. The axial force of the pile at variable cross-section has a sudden change. The side friction of the lower half of the pile is large. The side friction of the upper part of pile is less because of the existence of steel pipe. Pile tip resistance is an important part of the bearing capacity of pile foundation. The calculated results of pile axial force are close to the measured results, which indicates that the modeling method and parameter selection are suitable. The variable cross-section can improve the bearing capacity of pile foundation, but the position of cross-section should be moderated. The thicker the steel pipe and the denser the distance between the shear rings are, the more obvious the lateral stiffness of the steel composite pile is. © 2020, Central South University Press. All right reserved.