Conventional compressive strength parallel to the grain and mechanical resistance of wood against pin penetration and microdrilling established by in-situ semidestructive devices

This paper compares semidestructive and destructive wood testing methods. The semidestructive methods used were pin pushing, screw withdrawal, dynamic pin penetration, microdrilling, and a new construction of a diagnostic device for an in situ timber assessment based on the principle of measuring the conventional strength by means of a small size loading jack in a drilled radial hole of 12 mm in diameter. To examine the differences between the methods, we conducted measurements using four softwood beams, 1–2 m long. The aim was to discern the variability of properties caused by the distribution of structural properties along the radius and the length of beams incorporated in historical constructions of trusses. The accuracy of the prediction of mechanical properties as measured by semidestructive devices was verified using correlations with mechanical properties as established by standard tests in compliance with EU standards. The test results show a very good correlation of conventional strength with wood density and strength established in standard samples in compression parallel to the grain.