This paper examined the effectiveness of four prominent masonry building codes, namely,
MSJC-2011, AS3700-2011, NZS4230-2004 and CSA S304.1-04 in predicting the in-plane shear
strength of PGM walls based on the results of 89 experimental test specimens. The main conclusion of this research is that all of these code provisions are highly unconservative in predicting the shear strength of PGM walls.The minimum value for Vtest/ Vcalc was between 0.28 and 0.5 for all codes. This means that for some test results the shear strength predictions are more than three to four times higher than the test results. Consequently, the relevant code provisions need to be revised immediately as it poses a potentially life threatening problem where these shear strength values have been incorporated into structural lateral load resisting systems.The MSJC-2011 and AS3700-2011 over predicted the
shear strength of more than 70% of the test specimens,indicating that the degree of unsafety is higher in these two codes. However, the narrower scatter and smaller standard deviation of Vtest/Vcalc in MSCJ-2011 show that this code is less biased toward most of the parameters included in the shear strength equation.According to the results from both univariate and multivariate regression analyses, the effect of vertical reinforcement is underestimated in the shear strength expressions of all masonry codes. The available data suggests that by decreasing the percentage of vertical reinforcement or by increasing the vertical reinforcement spacing, the value of Vtest/Vcalc reduces and the prediction becomes more unsafe. The spacing between vertical reinforcement seems to be a signifi cant contribution factor in the shear strength of PGM that is not currently considered in the shear equation of the selected codes. Although the term fm’ is not directly refl ected in the provisions of AS3700-2011, the AS3700-2011 is the least biassed code when considering the effect of fm’ and the other codes placed excessive weight on fm’. Finally, a proposed equation has been suggested, which uses modifi cation factors 1 = 0.7 and 2 = 0.56 for the Vm and Vs components respectively in the expression of MSJC-2011, in order to obtain a better estimation of the in-plane shear strength of PGM walls. The new equation has an average Vtest/ Vcalc of 1.09, and standard deviation of 0.35. The new equation over predicts the strength of 39% of the specimens compare to the MSJC-2011equation which over predict the strength of 71% of the specimens.