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

Deformation characteristics of brick masonry under cyclic compression can p rovide vital information regarding material ductility, stiffness degradatio n and energy dissipation capacity. Cyclic biaxial compressions of five prin cipal stress ratios were applied to half-scale sand plast brick masonry squ are models and the stress-strain curves of envelope, common point and stabi lity point were established. The peak (failure) stresses of these curves we re used to obtain a family of failure interaction curves which can be expre ssed in terms of principal stress invariant. A general formula was proposed to obtain the cyclic stress-strain envelope, common point and stability po int curves. The envelope, the common point and the stability point curves c an be drawn on the absolute stress-strain coordinate system for any princip al 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, p rovided that cyclic uniaxial strength is known. Fifty-two half-scale brick panels were tested for the principal stress ratios considered.