Stress‒strain curves for masonry materials exposed to fire action

On the basis of the results obtained by an extended experimental campaign aimed to the mechanical characterization of main masonry materials subjected to fire action, the variation factors of compression strength, ultimate strain in absence of preload and the apparent modulus of elasticity were detected in function of the temperature increasing. The stress‒strain readings permitted to define sets of couples of data on which an uniaxial constitutive law, in comparison to those proposed by European standards, is defined and subsequently validated for each tested material. The error indexes produced by the various constitutive models are also determined and compared. The out-of-plane mechanical behaviour of the horizontal cross sections of full units masonry panels is then investigated: the method adopted permitted to define the axial force–bending moment crushing domains for increasing exposure time to nominal fire, considering the different types of stress–strain–temperature constitutive relations.