Strength of masonry made of ceramic brick with ground and unground surfaces (comparison of Russian and European norms)

Introduction. In recent years, much attention has been paid to the issues of reducing labor costs and increasing the reliability of test results of masonry ceramic wall products (brick, stone, and blocks). It is noted that when determining the masonry strength limit, the levelling of brick support surfaces is performed with mortar. However, when levelling the support surfaces by grinding, the masonry strength limit is artificially overestimated by at least one grade. In order to increase the reliability of erected buildings and structures, Note 1 to Table 6.1 of SP 15.13330.2020 “Masonry and reinforced masonry structures” gives an indication of the need to introduce appropriate correction factors in determining the strength of masonry. In the previous version of the SP, the values of reduction factors were adopted without appropriate justifications.

Aim. To justify reduction of design compression resistance of masonry made of ceramic soft-mud brick (when determining its compressive strength with grinding of supporting surfaces) in order to increase the reliability of erected buildings and structures.

Materials and methods. Comparison of normative and calculated values of the strength of masonry made of ceramic soft-mud brick on conventional mortar according to the norms of the Russian Federation, as well as Britain and Germany, on the basis of which the European norms have been developed.

Results. The conducted comparison of British, German, and Russian norms showed that the calculated values of masonry strength given in the norms of European countries are lower than those in the norms of the Russian Federation due to higher safety factors.

Conclusions. The decrease in the design compressive strength of masonry made of ceramic soft-mud brick by 10 % (when grinding the supporting surfaces to determine the compressive strength) is recognized as reasonable.

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