Advanced Numerical Model for Historical Masonry Structures Subjected to Seismic Sequences

The seismic assessment of historical masonry constructions presents significant challenges due to the nonlinear behavior of materials and geometric complexity. Predicting their seismic response becomes even more difficult when subjected to seismic sequences. To overcome this challenge, a methodology is proposed that integrates Limit Analysis (LA) with pushover analyses on Finite Element (FE) models to assess seismic response while accounting for cumulative damage. By combining LA with FE models, the computational time required for pushover analyses is significantly reduced. The LA-based approach identifies the active failure mechanism and power dissipation at interfaces, enabling the localization of inelastic deformations. The FE model concentrates material nonlinearities only at interfaces involved in the failure mechanism – where most energy dissipation occurs – while the rest of the structure remains linear elastic. This enables the evaluation of structural capacity and damage progression with limited computational effort. For a given design seismic sequence, the damage induced by each shock is assessed using the N2-method. A new active failure mechanism is then determined through the LA-based approach, incorporating cumulative damage by updating the properties of affected interfaces. A corresponding FE model is subsequently defined, accounting for damage from previous seismic events and the revised failure mechanism. The proposed methodology is benchmarked on a simple case study: a one-bay, two-story unreinforced masonry frame.