Strain gradient effect on the behaviour and strength of masonry

Twenty-four masonry prisms, including both grouted and hollow specimens, were tested to investigate the strain gradient effect on masonry compressive strength. Results showed that a reduction in load capacity as a result of an increase in eccentricity is more significant for grouted prisms than for their hollow counterparts. At a relatively large eccentricity to thickness ratio, e/t, hollow prisms attained a higher ultimate load than grouted prisms. Compressive stresses calculated at the extreme fibre using linear elastic analysis showed that the strain gradient effect increases with an increase in the eccentricity for grouted prisms, whereas the increase is marginal for hollow prisms. Coefficients for the equivalent stress distribution block, based on experimental stress–strain curves, were obtained for prisms under eccentric loading. An evaluation of the rectangular stress block used in both the American design code and Canadian design standard showed that the rectangular stress block provides an adequate and somewhat conservative estimate of masonry compressive strength and this conservatism increases as the strain gradient effect increases.Key words: masonry, strain gradient, eccentricity, compression, prisms, rectangular stress block, code, standard.