Cyclic biaxial stress-strain curves of masonry: a generalised approach

Deformation characteristics of brick masonry under cyclic compression can provide vital information regardʹ ing material ductility, stiffness degradation and energy dissipation capacity. Cyclic biaxial compressions of five principal stress ratios were applied to half-scale sand plast brick masonry square models and the stress-strain curves of envelope, common point and stability point were established. The peak (failure) stresses of these curves were used to obtain a family of failure interaction curves which can be expressed in terms of principal stress invariant. A general formula was proposed Co obtain the cyclic stress-strain envelope, common point and stability point curves. The envelope, the common point and the stability point curves can be drawn on the absolute stress-strain coordinate system for any principal stress ratio using an interaction curve and a relation between principal stress ratio and strain at peak stress. The study allows the determination of peak stresses of envelope, common point, and stability point curves of brick masonry under any combination of cyclic biaxial compressive stress, provided that cyclic uniaxial strength is known. Fifty-two half-scale brick panels were tested for the principal stress ratios considered.