Evaluation of the historic wooden structure condition based on the results of non-destructive tests

Abstract

Deformation of wooden roof structures is the effect of strength parameters reduction caused by biological corrosion, passage of time, looseness in joints and assembly inaccuracies. It is a significant problem, especially in buildings built several hundred years ago. Over many years of operation, historical structures are exposed to various loads, not only from their own weight or from external environmental influences (wind, snow). There are also accidental loads such as fires or warfare. Repairs and reconstructions, carried out as a result of accidental damages, are also important for the building structure. Renovation processes often influence on changes in the static scheme of the originally constructed structural system. Rheological phenomena of structural elements and joints have a significant impact on the redistribution of internal forces.In the paper the thorough condition evaluation of the historical church building is presented. The evaluation is performed with the use of non-destructive testing (NDT) methods. The analyzed church building was built in 1579–1601. Throughout its history, it was rebuilt after a fire when the structure of the roof and ceiling above the main nave was reconstructed. Then the roof covering was changed from heavy ceramic tiles to light sheet metal covering, and finally the sheet metal was replaced with metal roof tiles. In the meantime, the roof structure suffered damage resulting from the war, and a part of the roof structure had to be replaced. The current condition of the roof truss was analyzed using finite element method (FEM) software. The influence of the condition of carpentry joints on the deformation of the roof truss was analyzed. The duration of load (DOL) effect on the deformation of structural elements, as well as the influence of biological corrosion and uneven distribution of wood strength parameters in individual structural elements were considered. Based on the presented detailed analysis of the condition of the historic wooden structure using NDT methods, suggestions regarding the general applicable area in historic structures were formulated.