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The present paper is a review of the research works carried out on the cohesive crack model and its applications at the Politecnico di Torino during the last decade. The topic encompasses experimental, numerical and theoretical aspects of the cohesive crack model. The research work followed two main directions. The early work concerns the development and the implementation of the cohesive crack model, which has been shown to be able to simulate experiments on concrete specimens and structures. It is referred to as the dimensional analysis approach, since it succeeds in capturing the ductile-tobrittle transition by increasing the structural size owing to the different physical dimensions of two material parameters: the tensile strength and the fracture energy. On the other hand, the later research direction aims at extending the classical cohesive model to quasibrittle materials showing (as they often do) fractal patterns in the failure process. This approach is referred to as the renormalization group (or fractal) approach and leads to a scale-invariant cohesive crack model. This model is able to predict the size effects even in tests where the classical approach fails, e.g. the direct tension test. The two research paths, therefore, complete each other, allowing a deeper insight into the ductile-tobrittle transition usually detected when testing quasi-brittle material specimens or structures at different size-scales.

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Abstract. Natural sintering in ice is a fundamental process determining mechanical properties of various ice forms. According to the literature, limited data are available about the complex subjects of snow sintering and bond formation. Here, through cold laboratory mechanical tests with a new shear apparatus we demonstrate time-dependent effects of isothermal sintering on interface strengthening at various normal pressures. Measurements showed that interfacial strength evolved rapidly, conforming to a power law (mean exponent ≈ 0.21); higher pressure corresponded to higher initial strength and sintering rates. Our findings are consistent with observations on homogeneous snow, provide unique records essential for slope stability models and indicate the significant importance of normal load on data interpretation.

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