ABSTRACT
Unreinforced masonry (URM) walls are highly sensitive to non-proportional loading histories, particularly when foundation settlement precedes lateral loading. In such cases, pre-damage induced by settlement can significantly affect the subsequent structural response and cannot be adequately represented using proportional loading assumptions or equivalent reduction factors.
A Total Sequentially Linear Analysis (Total SLA) framework is developed to investigate the combined effects of boundary conditions, geometry, and settlement-induced pre-damage on the pushover response of URM walls. The numerical model represents masonry units as linear elastic continua and concentrates nonlinearity within zero-thickness interface elements governed by discrete damage modes. Settlement and pushover are applied sequentially within a unified event-driven formulation, allowing damage states to be inherited across loading stages.
The results show that the initial elastic response is largely insensitive to the top boundary conditions, whereas significant differences emerge during the softening phase. Fixed-top configurations exhibit a more gradual degradation of stiffness. Cantilever and free-top conditions, in contrast, show sliding-dominated behavior. Settlement causes irreversible damage, reducing both stiffness and peak capacity during subsequent pushover loading. The effects are amplified in walls with openings. These results demonstrate that neglecting load-path dependency may lead to inaccurate predictions of stiffness degradation and peak capacity in URM walls.
