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Soundness assessment of historic structural timber by the use of non-destructive methods

Kandemir, Ayşenur
The use of non-destructive testing (NDT) methods was needed for the conservation studies of historic timber structures. The aim of this study was to develop combined use of ultrasonic pulse velocity (UPV) measurements and infrared (IR) thermography, together with visual analyses for soundness assessment of timber. An important timber structure in Ankara, Aslanhane Mosque and traditional timber dwellings, in Ayaş and İstiklal District were selected for in-situ analyses. Representative laboratory samples such as mud brick, fired brick, mud mortar, mud plaster, lime plaster, historic timbers of different species and some new timbers were used for analyses in the laboratory to develop reference data for in-situ analyses. This study has shown that direct and indirect UPV measurements taken parallel to fiber direction were good at estimating the soundness of timber elements. UPV measurements taken from timber samples were affected by atmospheric humidity, at which the timber was in equilibrium with or by its water content, cuts of timber and type of species. Quantitative Infrared thermography (QIRT) was good at soundness assessment and defect inspection of timber. The study showed that, the even or heterogeneous distribution of surface temperatures, different thermal inertia characteristics, reflected by the rates of heating and cooling of materials and their ratios to sound timber were good parameters to assess the state of deterioration of timber elements, dampness problems and the compatibility of neighbouring materials with timber. The joint use of QIRT and UPV methods combined with laboratory data has enhanced the accuracy and effectiveness of the survey.