Shapes of loading surfaces of concrete models and their influence on the peak load and failure mode in structural analyses

This paper focusses on the influence of the deviatoric shape of the employed loading surface on the predicted failure of concrete. For this purpose, the Extended Leon Model (ELM) [1] and a multi-surface model are considered. The multisurface model consists of three Rankine surfaces and the Drucker–Prager surface. Whereas the Drucker–Prager surface is characterized by a circular shape in the deviatoric plane, the ELM accounts for the dependence of the strength of concrete on the Lode angle. It is characterized by an elliptic loading surface in the deviatoric plane. The eccentricity e defines the out-offroundness. It allows a smooth transition from a circular (e=1) to an almost triangular shape (e~~0.5) of the loading surface in the deviatoric plane. The significance of the deviatoric shape of the loading surface on the predicted peak load and failure mode of concrete structures is investigated by means of two example problems: a plane-strain compression test characterized by compressive failure and an anchor-bolt test characterized by shear failure.