Comparative analyses of contact algorithms for interface modelling in non-linear soil structure interaction.

The response of a structure to dynamic loading is collectively affected by the interaction between the foundation and the underlying soil surrounding the foundation. SSI can have considerable influence on the calculated structural response due to geometrical and material non-linearities of the interface. The paper aims to establish appropriate contact formulations for the soil structure interface elements through the direct method of analysis. The geometric non-linearities associated with the interface; primarily sticking and slipping are investigated using both kinematic and inertial interaction methods. A series of simulations are performed on a symmetric structure resting on a soil domain with non-reflecting boundaries by applying quasi-static and cyclic loading in MASTODON, a MOOSE based software application developed by the Idaho National Laboratory. The tangential behavior at the interface is simulated using a simple Coulomb friction type formulation. The shear stresses and strains are obtained at the interface and compared to the theoretical values. A thin-layer-element based interface formulation is also developed using a phenomenological soil model I-SOIL in MASTODON, which takes material damping into account. Upon establishing the appropriate contact formulation for the interface, a full-scale soil-structure interaction analysis is performed. The response at the interface is compared using algorithms like Lagrange Multiplier, Penalty and Kinematic contact methods in ABAQUS and MOOSE.