The assessment of Italian trusses: survey methodology and typical pathologies

The triangular truss is the most typical structural frame of Italian historic roofs. Mostly, but not exclusively, used to transfer vertical loads to walls, it has been developed during centuries into different geometrical compositions by using also different wood species and materials. The aim of this article is to describe the most typical features of the Italitan trusses and the survey procedures by using practical examples taken from hundreds of inspected structures. The complete assessment of a roof structure is an interdisciplinary activity, while this article is intended to present the point of view of the wood technologist, only partially considering the structural aspects. The survey is performed on the basis of a step-by-step procedure, with increasing levels of analysis: starting from a general analysis of the structure as a whole to the analysis of the single members and connections, gaining so far more and more detailed information, which can explain the results of the previous level of analysis. The most common pathologies occurring on timber trusses and structures are also described. Finally, before general conclusions, a quick case study, based on a roof structure from the beginning of 19th century, is shown, presenting the principal results obtained.