Assessment of unreinforced masonry cross sections under eccentric compression accounting for strain softening

The mechanical behaviour of unreinforced masonry cross sections subjected to eccentric compressive loading has been studied through laboratory tests, analytical procedures, and numerical models. Several macroscopic constitutive models have been implemented in beam-like analytical approaches in order to derive axial force – bending moment limit domains. This paper investigates the influence of different macroscopic constitutive models and strain softening on the strength domain evolution from the elastic limit state to the ultimate limit state. Simplified equations are proposed for the Eurocode 6 constitutive model and strength-degrading stress–strain relationships. The corresponding limit strength domains and those derived from other constitutive models are compared to experimental data available in the literature. It is shown that more conservative estimates of ultimate moment capacity are obtained if some of the proposed equations, or those corresponding to the elastic-perfectly brittle constitutive model, are used. Finally, evolutionary strength domains defined in a dimensionless axial force – bending moment – strain ductility space were developed to investigate how bending moment capacity changes with masonry ductility in compression. Such domains could be implemented in equivalent frame models to simulate moment capacity variations with deformation demands on individual macro-elements as static pushover analysis proceeds.

► The influence of masonry strain softening on bending moment capacity of URM cross sections has been investigated.
► Classical limit strength domains have been derived for strength-degrading constitutive models.
► Evolutionary strength domains have been proposed to consider strain softening in the structural assessment.