Shear resistance of masonry walls and Eurocode 6: shear versus tensile strength of masonry

In the case of masonry structures subjected to seismic loads, shear failure mechanism of walls, characterised by the formation of diagonal cracks, by far predominates the sliding shear failure mechanism. However, as assumed by Eurocode 6, the latter represents the critical mechanism for the assessment of the shear resistance of structural walls. The results of a series of laboratory tests are analysed to show that in the case of the diagonal tension shear failure the results of the Eurocode 6 based calculations are not in agreement with the actual resistance of masonry walls. The results of calculations, where the diagonal tension shear mechanism and tensile strength of masonry are considered as the critical parameters, are more realistic. Since the results of seismic resistance verification, based on the Eurocode 6 assumed sliding shear mechanism, are not in favour of structural safety, it is proposed that in addition to sliding shear, the diagonal tension shear mechanism be also considered. Besides, in order to avoid misleading distribution of seismic actions on the resisting shear walls, the deformability characteristics of masonry at shear should be determined on the basis of experiments and not by taking into account the Eurocode 6 recommended G/E ratio.