Nonlinear Buckling Analysis of Piles with High-Rise Pile Cap

To study the buckling stability of piles with high-rise cap widely used in bridge and harbor engineering, the advantages as well as the insufficiency of traditional analysis methods (e.g., the method using the minimum potential energy theory and variational method by treating the pile shaft as ideal axially-compressed bars) were first discussed. Then, based on the second type of stability problem (i.e., the pile shaft is viewed as an unideal bar with initial quality defects) and the nonlinear finite element method (FEM), a new method was presented to consider the nonlinear pile-soil interaction. And influencing rules of various factors especially those initial defects on the critical buckling load P_cr were discussed through the numerical analysis model by ANSYS. The analysis result shows that, with the increase of the free length at the pile top from 2.5m to 5.0m, the P_cr will decrease to a relative extent of 32.5%, and similar changing rules are also found with the increasing degree and location of initial bending and necking along the pile shaft. Moreover, the increasing inclination degree of pile shaft will result in an obvious linear cut down of P_cr. Finally, the present method is applied to analyze the data from a site loading test, which found a good agreement between the calculated buckling load 18.27MN and the measured failure load 17.28MN with a relative error of 5.7%.