Some practical aspects of the photoelastic stressmeter in concrete.

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.