Some analyses simply do not fall within typical ductile yielding-based FEA studies. One such repair project involved evaluation of a collapsed internal brick arch structure. For this study, the brittle failure mode of both the brick and mortar had to be taken into consideration. Fracture toughness properties were researched and used in Abaqus’s XFEM fracture mechanics solver. A quarter symmetry model was created, startup temperatures applied in a heat transfer program, and then these temperatures mapped to a thermal-stress XFEM solution. Maximum tensile stresses were set for both the brick and mortar within a defined region, where once the thermal stresses reached this value, crack origination occurred.
As the thermal stresses increased, the cracks grew based on the fracture toughness of these brick wall components. XFEM was able to reproduce exactly where the initial cracking occurred in the brick wall, which occurred along a horizontal mortar seam right at a major point of flexure. Observing that such a weakness (the horizontal mortar) was at the highest bending stress of the brick wall, a change was made to the brick arch design to alleviate this design issue. Retesting under identical loading showed the new design no longer had the mortar placed in an area of such high bending stresses. The new design was substantially stronger and as of this writing, there have been no reported issued with this revised design.
