Semi-numerical micromechanical model for viscoelastic microcracked masonry
Abstract
This paper proposes a semi-numerical model providing accurate estimates for the mechanical behaviour of viscoelastic microcracked masonry. It relies on two steps. The first one approximates the creep behaviour of the microcracked mortar by coupling-in the Laplace-Carson symbolic space-the Griffith's theory to the Ponte-Castañeda & Willis (PCW) micromechanical scheme accounting for microcracks interactions and spatial distribution. The PCW model is an accurate alternative to the dilute and Mori-Tanaka model frequently used to homogenize microcracked media. Accumulated damage is assumed to follow a power-law time evolution according to the Weibull's failure rate function. In the second step, by contratry to the periodic homogenization technique adopted previously in [36] which approaches the masonry behaviour, finite elements method is used to model the complete geometry of the masonry and compute accurately (up to the numerical error) its local behaviour. The sensitivity of the proposed model to the mesh refinement is validated by comparison to analytical solution. It is worth noting that the proposed model accounts for creep of both brick and mortar constituents following the Generalized Maxwell rheological model. As a first illustration, the proposed model is applied to a compressed masonry wall. For the sake of simplicity, only mortar joints are assumed to be microcracked with frictionless open cracks. Comparisons between panels with elastic and viscoelastic bricks show the additional softening effect induced by the brick's creep increasing thus the risk of failure.
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