Inauguration UNESCO Chair on Preventive Conservation, Maintenance and Monitoring of Monuments and Sites
Inauguration UNESCO Chair on Preventive Conservation, Maintenance and Monitoring of Monuments and Sites date:24-25 March 2009
3. Acoustic Emission Technique: crack initiation and damage accumulation is associated with energy release. The AE technique, detects transient energy waves emitted by a material as a result of stress redistributions. Besides the experience built up for the evaluation of masonry within short term and long term creep tests, its applicability has been looked for at a few case studies: Maegdentoren (Zichem, B); Castle Ter Laenen, (Geetbets, B), multi-storey building at Recife (Brazil). The technique is based on measuring emission of acoustic waves from (very small) cracks that are developed in the material at high stress level. The analysis of the intensity and of the frequency of appearance of cracks allows to identify the level of stress in material and more particularly how close the stress is to ultimate strength resulting into creep; the original theories on which this method is based are from the hand of Richter who studied earthquakes, however the same theory is applicable to masonry or even materials. The non destructive technique can be used as a monitoring tool and can correlate directly to understanding the risk for overloading structures. On site measuring of stress level can correct calculations that usually overestimate stress. Having correct information can contribute to preventive conservation.