R. LOVEGROVE and R. C. DE VEKEY
Building Research Establishment, Garston, Watford, UK
When a method for determining a property of a material has been established it is important to check that any changes do not alter, to any practical extent, the quantity to be measured. It has at various times been suggested that the method for determining the flexural strength of masonry, given in BS 5628: Part 1: 1978, should be altered by changing the number of bed-joints in the constant-moment zone. This paper presents theoretical and experimental investigations into the effect that such a change might have upon the characteristic strength. The observed changes are in broad agreement with those to be expected in theory. For example, changing from five bed-joints to three would increase the characteristic strength by about 15%. It is concluded that the number of bed-joints cannot be altered by more than one without producing a possibly unacceptable change in the observed characteristic strength.