MILAD M ALSHEBANI* and S N SINHA** * Al-Fateh University, Tripoli ** Indian Institute of Technology, Delhi

Experimental investigations were conducted on forty two specimens of half-scale sand plast (a form of calcium silicate) brick masonry panels to study the behaviour of the material under uniaxial cyclic compression in two orthogonal directions -normal to the bed joints and parallel to the bed joints. The mortar mix was 1:0.5:4 (cement:line:sand) by volume and the water-cement ratio was 0.95 by weight. Test data were used to establish evelope, common point, and stability point stress-strain curves, as well as energy dissipation capacity. Stiffness degrades and strength deteriorates with the increase in number of load cycles, greatly influenced by the intensity of the cyclic loading. The variations of stiffness degradation, with respect to envelope strain, plastic strain, load level, and energy dissipation ratio, are presented together with suitable mathematical expressions for these variations. This research indicates that linear elastic analysis of masonry under cyclic load can be performed up to a load level of 20% of failure load above which the stiffness remains constant. Plastic strain accumulation due to cyclic loading can be used to define the permissible stiffness degradation.