Keywords: zero-thickness interface, artificial scaling stiffness, soil-structure interaction, benchmark.

For the modeling of realistic soil-structure interaction interface elements are needed. These are important to incorporate the interaction effects. Interface elements connect the rigid body (structure) with the deformable body (soil). In addition, this allows the incorporation of important features e.g. sliding, separation and debonding of a thin zone. The use of such elements is also important to prevent mesh locking. Further by the use of interface elements, it is possible to use different material models. In general two major types of interface elements exist. The "zero-thickness" interface element proposed by Goodman and Beer. Further, the "thin-layer" interface element proposed by Desai et al. In the first kind of these elements the stiffness must be scaled to an unrealistic high stiffness to achieve adequate results in the computation.

Normally the stiffness scaling is introduced by an artificial parameter which acts as a multiplicator for the scaling. Desai et al. argued that the high stiffness is not realistic and that the transition zone between the soil and the structure has a thickness. The choice of stiffness scaling in these elements has a major influence on the computed behavior and the results of such models. The stiffness scaling in zero-thickness interface elements is investigated using different case studies.

These studies are carried out using different numerical simulations which are simplified examples of soil-structure interaction. The studies start with a simple two block example where different loading cases are conducted: axial compression and tangential loading. The second study uses a verification example from Desai et al.. The third case is an elastic longitudinal block benchmark example by Hird et al. This case study is used to compare the influence of the stiffness scaling to an analytical solution.

The goal of these study is to show the importance of the stiffness scaling in zero-thickness interfaces elements. The variety which can be found in the literature between the thin-layer thickness approach and the zero-thickness interface elements will be discussed. The results of these studies show the importance for a defined use of the stiffness scaling parameters.

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