Technology Transfer Department

Application sectors

Problem to solve

Intending to safeguard architectural and cultural heritage, the assessment of the health of timber is crucial, though challenging, due to the organic nature of wood and to the uncertainties of its preservation state. The use of suitable instruments and qualified personnel is therefore of fundamental importance to provide correct and exhaustive information to those who need to intervene on this material to guarantee its conservation and structural functionality.

Description

Different intervention methods may be used to maintain, repair or reinforce timber structures. Therefore, a thorough recording and analysis of their conservation state and moreover a thorough understanding of their original and present structural behaviour must be available to define the more suitable and compatible for each intervention case. Geometrical survey is the first step of the assessment, followed by Visual inspection – strength grading by means of the Italian Standard UNI 11119. Then Non-destructive tests (NDTs) can be carried out as complement to the visual inspection but, more importantly, to assess the depth of decay of each element. Three NDTs are commonly used, namely pin penetration, drilling resistance and ultrasound tests. Pin penetration tests are widely used for evaluating pole decay, or standing trees as well as sawn lumber density, since it provides fast and cheap results and induces minor damage to the timber member. Drilling resistance tests measure the energy required to perform the micro-drilling of wood at constant cutting speed by a standard drill. The advantage of this method is the access to non-visible areas of the timber elements: moreover, the drilling resistance energy may be transformed into a resistance measure The ultrasonic method gives an estimation of the mechanical properties of existing timber elements correlating the measured mean transmission velocity of ultrasound waves to the dynamic modulus of elasticity. By combining the information of the NDTs it is possible to obtain damage maps evidencing critical sections and to determine the residual/effective cross section of timber elements. The different NDTs provided important information regarding the conservation level of each element.

Research group involved