Research on residual bending capacities of used wood members based on the correlation between non-destructive testing results and the mechanical properties of wood

Abstract

To quantitatively assess the residual strength of wood members after rot and infestation using non-destructive testing (NDT), the multi-point Resistograph method was applied to test six used wood beams with initial imperfections. Each wood beam was then divided into a shorter segment for mechanical tests and a longer one for bending capacity tests. With the help of finite element analysis using ANSYS, bending capacity is predicted by taking account of the initial imperfections. Results show that there is a significant correlation between drill resistance values and strengths for small specimens. Therefore, the strengths of wood at other measurement points may be obtained through drill resistance values. The beams showed a near linear behaviour up to the maximum load with poor ductility performance in bending capacity tests. It can also be found that the effects of initial imperfections on failure modes and ultimate loads are significant. The lateral side of specimen BA1 has serious infestation and the bottom of BA2 has a long longitudinal crack, the ultimate bearing capacities of these specimens are respectively only 67.6% and 64.8% of BA3, which has fewer cracks. BB1 and BB3 have knots at the bottom and their ultimate bearing capacities are respectively 83.9% and 81.0% of BB2, which has fewer cracks as well. Furthermore, there is quite good agreement between test results and numerical prediction using strength values obtained by NDT results. Therefore, the bending capacity of used wood beams can be obtained using NDT, which can provide the basis for the protection and retrofitting of wood structures.