IN SITU NON-DESTRUCTIVE EXAMINATION OF TIMBER ELEMENTS

Structural timber is a traditional construction material. Timber structures belong to essential parts of almost all historical buildings, especially roof and ceiling structures. Their actual condition affects durability of the whole building, therefore it is necessary to check the conditions of the structure regularly and take care of possible undesirable changes. If these structures have historical value we have to use non-destructive or semi-destructive methods during this investigation. Penetration methods in combination with ultrasonic method are used nowadays [1]. Penetration devices are suitable to determine the density, surface and internal biological degradation, growth defects and moisture content of the element [2]. The density and the velocity of ultrasonic wave represent input information to derive dynamical modulus of elasticity. Penetration devices work on the principle of measuring the depth of penetration of a steel tip or on the principle of resistance drilling. Another method of determining the density of inbuilt element is the radial core. These methods are semi-destructive. It is the subject matter of the author's research to replace these penetration methods by radiometric measure of mass density. This method is based on the principle of gamma rays dispersion or on the principle of gamma rays absorption in a timber element. Radiometry as a measurement of density is often used for concrete constructions and asphalt pavement now. This measurement can be applied to the inbuilt elements, which is its a main advantage [3].