A finite element program is developed to depict the behavior of a sheet pile interlock connection in an axial pull test. Two types of sheet piles, PS32 and PSX32, are considered. The thumb and finger in the interlock of a sheet pile will provide three contact points for connection with another sheet pile. The problem is highly nonlinear in nature which involves large deflections and rotations, elastic-plastic material response, and a nonlinear boundary effect due to multi-contact surfaces.

The Updated Lagrangian formulation is adopted in this study. When the response is in elastic range the Updated Lagrangian with Transformation is used while the Updated Lagrangian with Jaumann stress rate is employed when the element starts to yield. An elastic-plastic with isotropic strain hardening material model is used. The yielding of an element is detected by the Von Mises yield criterion. The finite element formulation also includes a moving contact algorithm to incorporate with both geometric and material nonlinearities. Incremental potential of contact forces for a discretized system is constructed such that geometric compatibilities are maintained between contacting bodies. A method to calculate contact tractions from residual load of internal element stresses is employed. The incremental equilibrium equation is solved by a Newton-Raphson technique. Convergence criteria based on incremental displacement, incremental internal energy of the system, and the changes in contact forces can be chosen to advance or terminate the iteration process.