UDO MEYER Arbeitsgemainschaft Mauerziegel e. V. Bonn
Restrained movements due to shrinkage or thermal action are among the main reasons for cracking in masonry. Cracks due to restrained stresses parallel to the bed joints can be limited by bed joint reinforcement. Control of crack widths may be necessary for reasons of durability (external members) and aesthetics. The paper describes the basic interdependence between the relevant material properties and the necessary minimum ratios of reinforcement. Information about the tensile and flexural strength of masonry parallel to the bed joints is summarized and a formula for the determination of relevant steel stresses at a crack, based on bond theory, is developed. The results of the calculations were checked by tensile tests on reinforced walls. The correlation between the calculated and observed crack widths was acceptable. Based on these results, minimum ratios of reinforcement for masonry under different boundary conditions are proposed and design aids for the determination of these values are presented.