Simplified and Numerical Approaches for the Evaluation of the Plan Irregularity in Masonry Buildings

Although existing masonry buildings do not generally exhibit a high vertical irregularity, they can be affected by a relevant plan irregularity. In this manuscript simplified and numerical studies are adopted to investigate the plan irregularity of a sample of 143 residential masonry layouts. Initially the structures are divided according to building typologies; then, a simplified methodology to evaluate the plan irregularity is used to classify the structures. The results of the simplified procedure, expressed in terms of scores or percentages of irregularity are compared with the outcomes of nonlinear static analysis executed over case studies representative of wider building classes. The work shows that the evaluation of the eccentric ratio between mass and stiffness barycentre may lead to proper plan irregularity scoring coherent with the numerical results, while geometrical classifications on the architectural shape omitting the contribution of resistant area can overestimate the irregularity effect.