9-Arms Probe for Measuring Deformations of Cementitious Materials.

Based on the concept of measuring six strain-components within a cast element a device, that is described in the paper, has been developed at the Warsaw, Poland, Polytechnic Institute. It consists of 9 arms of equal length interconnected by nodes. The arms are provided with sensors (strain gages) chosen for each particular tested material and anticipated magnitude of strain. Under the assumption of symmetry of the strain tensor the device supplies three additional readings which enables errors to be assessed and correct results to be obtained even in the case of a simultaneous malfunctioning of three gages. Operation of the probe is shown on a practical case.