Ultrasonic methodology in in-situ investigation of historical masonries: a theoretical-experimental experience.

Ferrari, Giacomo and Andrea, Morotti (2000) Ultrasonic methodology in in-situ investigation of historical masonries: a theoretical-experimental experience. In: 15th World Conference on Non-Destructive Testing, 15-21 october, Roma, Italia.

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Abstract

The use of NDT ( Non Destructive Testing ) has a great importance in the renovation field, due to the possibility of accomplishing researches during the preventive and diagnostic phase on buildings of historical and artistic interest. The application carried out on the tower of the Galliate castle, which is based on the utilisation of indirect ultrasound surveying technique, was aimed at the experimental data re-processing, in order to correctly evaluate the static condition of the case study. The method employed for the sonic characterisation of the masonry facings, previously identified on the tower, is essentially based on the measurement of the time needed by ultrasonic waves (in this experimentation, the frequency being 54 KHz) to cover the distance between the transmitting and the receiving probe, positioned on an point of contact which is integral with the material means to be examined, where the propagation motion of the ultrasonic waves is generated, being this produced by the transformation of the electric impulses by means of a special instrument which, in this monitoring session, consisted of an ultrasonic equipment, manufactured by Controls s.r.l.. The technique adopted for this experimentation has been operationally defined on the basis of the reciprocal position of the probe with respect to the geometry of the sample to be tested, which is known as indirect or homeosuperficial transmission, where both probes are applied on different points of the same side of the wall facing to be characterised from the sonic point of view. The measurement was made by using a hypothetical grid with a 200 x 50 cm rectangular mesh represented by the intersection of pre-defined courses with certain vertical alignments of the joints of the masonry’s solid bricks. The method used to investigate the statistical dependence between causes (stress states  acting on the masonry) and effects (velocity v of sound propagation), holding true the casual antecedence constraint between the two variables, was that of regression analysis. Points ( , v) were interpolated following some considerations, by sorting the velocities having the same probability values obtained from their respective distribution functions. The analysis allowed to obtain some curves, referred to as “Stress possibility curves for compressive strains” that establish the relations of functional dependence between the observed physical quantities, or define the most probable variability range of and v for the masonry that has been monitored from a sonic point of view. The method which allowed us to emphasise the dependence between the causes and the effects was the regression analysis; therefore, by using a statistical elaboration, the “dependence curves” were obtained. The performed experiment allowed us, firstly to express remarks and considerations with respect to the static condition of the case study, secondly to implement an evaluation control methodology, in structural terms, of monumental buildings’ individual parts.

Item Type:	Conference or Workshop Item (Poster)
Additional Information:	Paper available on the CD containing the Conference Proceedings
Uncontrolled Keywords:	building, castle, ultrasound, masonry, tower,waves, receving probe, stress, velocity
Subjects:	600 Tecnologia - Scienze applicate > 690 Edifici
Depositing User:	ing Giacomo Ferrari
Date Deposited:	07 Sep 2007
Last Modified:	20 May 2010 12:01
URI:	http://eprints.bice.rm.cnr.it/id/eprint/419

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