A regression analysis for estimating the strength of skin timber using the density and boring diameter

Skin timber can be defined as hollow timber that is circular or rectangular in cross section with an inner cavity whose cross-sectional area is more than 90% of the total cross section. Using small samples instead of full-scale skin timber, we examined the different failure types and the strength properties of bored and non-bored specimen. From these results, we prepared strength estimates as a function of the boring diameter. Adding wood density as a second independent variable, we were able to estimate the strength properties more accurately. We conclude that it will be important to perform similar measurements and regression analyses for full-scale skin timber is need, and development of hybrid structure using skin timber which can complements the strength loss of it due to its boring area is also required.