A PROPOSAL FOR THE EVALUATION OF THE PENETROMETRIC PROFILES OBTAINED BY RESISTOGRAPHIC TESTS: QUALITATIVE ESTIMATION OF THE DENSITY OF TIMBER STRUCTURES FOR SUPPORTING THE INTERPRETATION OF THE RESULTS

Among the different testing techniques for timber structures, the common tests are based on slightly destructive methods which provide results of qualitative order. The resistance drilling tests, for example, are able to detect the decayed areas of the material. Nevertheless, the interpretation of the results is influenced by several factors: the correct execution of the test and the estimation of the damage, according to the comparison between decayed and non-decayed areas, supposed to be representative of a sane condition of the structure. Other testing methods for timber structures are very close to sclerometric tests, but the penetrometric tests allow a more effective control on the wooden element for interpreting the decay problems. The penetrometric tests, carried out through resistographic devices, provide a profile represented in a amplitude vs drilling depth graph. This result does not allow a direct correlation between the recorded amplitude and the density of the material. After several on-site applications of the resistographic tests, the authors carried out some laboratory tests trying to use the measured amplitude as a key-parameter for supporting the final interpretation of the data. During the tests performed in laboratory at fixed environmental conditions, a preliminary estimation through densiometric profiles of the density levels obtained for some specific wood categories was identified. The comparison between the profiles obtained from timber structures of an unknown type (the recognition of the wood type is a time-consuming problem) and the one interpreted in laboratory can provide an important support to the interpretation of the penetrometric tests results.