A multiscale approach for the seismic analysis of concrete gravity dams

In this article, the problem of cracking in concrete gravity dams subjected to seismic loadings is examined under a multiscale perspective. Preliminarily, the size-scale effects on the mechanical parameters entering the nonlinear constitutive models of the interface crack are discussed. From a wide review of existing experimental results, it is shown that the material tensile strength, the fracture energy, the friction coefficient and the concrete compressive strength are strongly size-scale dependent. This evidence pinpoints the necessity of performing experimental testing on large scale specimens to assess the value of the parameters to be used in nonlinear fracture mechanics simulations. Moreover, the size-scale dependency of the interface constitutive properties implies the necessity of updating their values during crack propagation simulations. To do so, interface properties are not given in input a priori, but they are selected at each step of the simulation according to the specified scaling laws. The numerical simulations, based on the finite element method and a generalized interface constitutive law for contact and decohesion implemented in the node-to-segment contact strategy, show the high sensitivity of the phenomenon of crack propagation by the parameters of the damage law used to degrade the cohesive zone properties in case of repeated cycles.