Synopsis
Values and distribution of concrete compression strain from prism and structural member tests have been reported by many investigators. Much of the information indicates that strain measurements in concrete are irregular and unpredictable. In this paper, tests are described which show that, for eccentrically loaded plain concrete prisms, the surface compression strain over the length of the failure zone can be assessed to within ± 20%. This strain is shown to be dependent upon the depth to the neutral surface and the depth of any tension concrete adjacent to the compression concrete. The length of the compression failure zone is related to the depth to the neutral surface, but does not appear to be affected by adjacent tension concrete. In studying the effects of different depths of compression and tension concrete, a theory of failure for concrete in compression was evolved. This theory suggests that the strain capacity of concrete in compression, and so the deformation capacity of structural concrete in general, is dimension- or size-dependent.
