APPLICATION OF THE LOAD/UNLOAD RESPONSE RATIO METHOD IN CATASTROPHIC FAILURE PREDICTION OF STRUCTURES

The Load/Unload Response Ratio (LURR) method is a new approach to predict the failure of heterogeneous brittle media, i.e. using the ratio between response rates during periods of loading and unloading to describe the damage state of the media. To show the effectiveness of the approach, this paper firstly evaluated the LURR time series associated with a loading and unloading experiment on a two-layer structure carried out in University of Naples in Italy. The result shows that the LURR time series climb to an anomalously high peak and then decrease rapidly prior to the final failure. Moreover, the rock failure acoustic emission (AE) experiment is conducted, and the experiment data is evaluated by the LURR method with macro-axial-strain as response. Results indicate that the LURR curve is very consistent with that of the two-layer structure experiment. Then the LURR curves are compared with AE energy rate and macro-axial-strain as response respectively. It is found both LURR values show identical evolution: initial stability, abmormity, peak value, and decrease charply prior to the final fracture. In order to determine the relation between LURR evolution and the damage of the structure, the LURR values are combined with damage variable (D) to provide the damage estimation of the structure. The results shown in the paper may suggest that the LURR method provides a new approach for the health assessment of large scale structures or ancient buildings and the prediction of engineering catastrophic failure.