Some practical aspects of the photoelastic stressmeter in concrete

• Main Author: Rose, Howard
• Published: University of Sheffield 1970
• Subjects: 624.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.572840

Further investigations are described in the development of a biaxial glass inclusion gauge as a practical instrument for internal stress determinations in concrete. With this technique the magnitudes and directions of the required host stresses are interpreted from the induced stresses in the gauge by photoelastic methods. Before discussing the new work the concepts and principal features of earlier stress gauges are described and existing knowledge of the photoelastic stress meter is summarised. Some elementary aspects of concrete shrinkage effects on the gauge readings are then discussed; the experimental evidence includes the problem of inclusion stresses produced by shrinkage and superposed external loads. The discussion continues with an assessment of stressmeter behaviour under the action of two-dimensional stresses of opposite sign. Experimental evidence is compared with a theoretical solution and other indirect stress measurements using conventional strain gauge techniques. The experimental results from both the shrinkage and compression-tension tests reveal significant anomalies in the inclusion stress distribution. Then comparisons are made with calculated conditions. This feature, which has not been considered by previous investigations, is discussed with reference to the assumptions implicit in the theoretical solutions. An explanation is proposed for the observed behaviour. Finally a practical application of the stressmeter in a buttress Jam is described and the readings are compared with calculated stress conditions for the buttress. Recommendations are made for the benefit of similar applications in the future. The thesis concludes by discussing the implications of the present results to the photoelastic stressmeter method of determining stresses in concrete and suggestions are made for topics of further study.