ABSTRACT
Figure 1: Schematic view of typical stress-strain curve for Stiffness Damage Test over a stress range of 0.5-5.5 N/mm 2. The resulting strain is monitored using three linear transducers placed at 120° to one another. The average area of the hysteresis loops over the last four cycles is normalised over the stress range to yield a value for the Damage Index. A second test has been developed separately, in which concrete cores are subjected to torsional loading [2]. The torsional testing arrangement is illustrated in Fig. 2. The application of torsion alone to a concrete core produces shear stresses on certain planes, equal in magnitude to the principal stresses, i.e. diagonal tensile and compressive stresses. Thus, the torsion test may be considered as an indirect tensile test on the concrete cores. The main objective of the work reported here was to combine the above two test methods into one unified test procedure and to extend the stress range used during cyclic testing. The Stiffness Damage Test has been added to the torsion test so that Damage Index results are obtained by subjecting cores in the torsion rig to low cyclic loading prior to taking the specimens up to failure. A comparison of Damage Index results obtained by means of various test specimen geometries is currently under investigation.
