The approach used in this work is based on idea of concentrating all the damage in the relatively weak joints and, if necessary, in potential tension cracks in the bricks. The joint interface constitutive model should include all important damage mechanisms. Here, the concept of interface elements is used. An interface element allows to incorporate discontinuities in the displacement field and its behavior is described in terms of a relation between the tractions and relative displacement across the interface. In the present work, these quantities will be denoted as
**, generalized stress, and
****
**, generalized strain. For 2D configuration,
** and
****
**, where and are the normal and shear components of the traction interface vector and and subscripts distinguish between normal and shear components of displacement vector.

(55) |

For a 2D configuration

(56) |

where and are Young's moduli, and shear moduli for brick and mortar, and is the thickness of joint. One should note, that there is no contact algorithm assumed between bricks, this means that the overlap of neighboring units will be visible. On the other hand, the interface model includes a compressive cap, where the compressive inelastic behavior of masonry is lumped.

2018-01-02