published_or_final_version / Civil Engineering / Master / Master of Philosophy

Under static of dynamic loadings, the junction (interface) between a structure-foundation system can experience contact, slip, separation and rebonding modes of deformations. Two interface models are proposed for simulation of interface behavior in finite element analysis of dynamic soil-structure interaction problems. The first element called the thin-layer element has (small) finite thickness. Geometrically, this element is similar to the continuum (soil or structural) element; however, its constitutive relations are defined differently. The normal behavior is defined as a function of the material properties and stress-strain characteristics of the neighboring continuum element. The shear behavior is defined in terms of observed shear stress-relative displacement behavior expressed as function of factors such as normal stress, number of cycles of loading and amplitude of load (or displacements). Mohr-Coulomb criterion is used to define activated sliding strength of interface. Modes of deformations are simulated by using appropriate stress redistribution iterative schemes. The second model called the mixed interface element has zero thickness. Both displacements and tractions are treated as primary unknowns. Constraints associated with modes of deformations are included using a variational approach. An incremental solution scheme is proposed. Material parameters related to the proposed models are evaluated from the results of sand-concrete interface tests in a Cyclic Multi-Degree-of-Freedom shear device. Accuracy of the proposed models are verified with respect to a number of example problems. In general, consistent and satisfactory results are obtained. For further verification and evaluation of these models, several soil-structure interaction problems are solved and detailed results are presented. It is observed that behavior of structure-foundation systems can be significantly influenced by interface conditions. An analysis based on bonded interface condition appears to underestimate actual response. Hence, it will be appropriate to include interface behavior in the analysis and design of structures subjected to dynamic and earthquake loadings.

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