The grouted reinforced masonry beam (GRM beam), being a composite of a reinforced concrete (RC) and a reinforced masonry (RM) beam, has been shown to have a shear capacity between that of a RC and a RM beam. It is believed that as the grout width to beam width (bg/b) ratio increases, the shear resistance of the GRM beam will increase proportionally. A review of published evidence provided no systematic data on the influence of the bg/b ratio on shear strength, vu. Hence an experimental study involving a total of sixteen beams was undertaken to investigate the bg/b effect. Of the sixteen beams, fourteen were built at one third scale. A review of literature provided no information on the effect of scaling GRM beams. Therefore, this study also investigated the size effect.

GRM beam results indicate an overall increase in vu (compared to vu of RM beams) due to the bg/b effect. Results also indicate that the size effect has a minor effect on vu, and hence it appears that third scale GRM beam studies are feasible alternatives to full scale studies.