Building Research Establishment

The use of flat jacks to carry out in-situ measurements of compressive stresses with minimal, easily repairable damage, is well documented in the literature. For structures accessible on two sides the eccentricity of stress in the section may be estimated, simply, by measuring the stress in each face. In this paper a technique is proposed for the measurement to be carried out from one face by use of different sized jacks or by changing the orientation of a rectangular jack. This allows the technique to be applied to cavity cladding walls forming the outer envelope of framed and loadbearing masonry buildings with no disturbance to the occupants. This laboratory trial demonstrates that the technique is feasible and is capable of giving a very good estimate of the stress state in such structures.