A penetration test to evaluate wood decay and its application to the Loggia monument

Facing the problem of restoration and consolidation of wooden beam floors and roofs of historical buildings and ancient masonry houses, it is important to evaluate wood decay in a reliable way. The techniques usually adopted require the taking of samples, laboratory tests, radiographs or ultrasound analysis, while tests in situ are usually based on yard practice and generally give only some qualitative information about wood condition. In the present work a method and an operative technique are proposed which make penetration measurements possible. The test can be regarded as an extension of the dynamic penetration test used for soil investigation and it is based on the pentration of a graduated rod, which advances by means of repeated blows of a rebound hammer. A preliminary study was done to identify and prepare the most suitable equipment. An attempt to find a possible correlation between wood flexural strength and penetration test results was also done and the correlation curve for spruce wood seems to give a reliable result. This technique was proposed and adopted for a broadbased investigation of the roof vault of the Palazzo della Loggia, a 16th century building in Brescia (Italy), and it gave useful indications of the extent and depth of the decay of the supporting wood structure.