Selected methods of diagnosis of historic timber structures - principles and possibilities of assessment

The paper presents a survey of state-of-the-art nondestructive and semi-destructive diagnostic techniques of testing timber structures and examples of their application. Nondestructive testing is a field of study which covers: identifying the mechanical and physical properties of materials and structural components, detecting material defects and discontinuities, and measuring the geometric dimensions of objects without affecting their performance. The nondestructive and semi-destructive methods are described in a systematic manner and the relevant equipment, technology and applications are discussed. The paper focuses on acoustic methods, resistance drilling techniques and radiography, which are suitable for detecting internal defects, decay and cracks, determining the location and dimensions of degraded areas and assessing the mechanical properties of structural timber members. Much attention is devoted to the techniques that are used in practice and have shown significant promise for future development. The results of several drilling resistance tests carried out on historic timber structures are presented.