Failure analysis of interacting masonry arch-wall structural systems: A micro-mechanical FEM insight

Masonry structural elements constituted by arches interacting with the spandrel walls are widespread in historical buildings, bridges and culverts, but the prediction of their behavior at failure both in presence of vertical and horizontal loads by means of adequate numerical modelling is still challenging. The difficulties arise because of the interaction at the interface between the arch and the surrounding wall, the latter typically behaving as a deep beam. The present paper proposes a viable general procedure to follow to predict their behavior at collapse. It is based on advanced Finite Element micro-modeling, where mortar joints are lumped to interfaces and units are meshed with plane stress elements. Bricks incorporate confined compression elastic-plasticity, whereas a cohesive zone model is used to simulate joint failure. The validity of the numerical approach is assessed through a comparison with some existing experimental results, obtained for arches built in a single and double rowlock-stretcher configuration and subjected either to a concentrated eccentric vertical load or a shear horizontal force applied at the base of one of the springing. Simulation results show that the proposed numerical model can effectively replicate load–displacement responses and failure modes. A further insight demonstrates that the response near collapse is governed by arch-wall interaction, progressing through three distinct stages: elastic deformation, strengthening through combined arch and wall failure, and collapse. Specimens with stretcher bricks exhibited delayed crack penetration, more uniform stress distribution, and enhanced deformation capacity—effects particularly pronounced under horizontal loading.