2013 Volume 59 Issue 3 Pages 152-161
To study the effect of degradation of structural wooden panels on the performance of nailed joints, plywood and medium density fiberboards (MDFs) were decayed forcibly by Fomitopsis palustris (brown-rot fungi) or Trametes versicolor (white-rot fungi) and strength tests of nailed timber joints with wooden panels were conducted. As a result, plywood was considerably deteriorated, and mass-loss when decayed by F. palustris was greater than with T. versicolor, but MDFs were hardly decayed by either fungus. Lateral nail resistance of wooden panels and shear strength of nailed timber joints were decreased by decay of wooden panels as side members and lumber as main members, but high moisture content seemed to greatly affect strength degradation of each member in the early stage of decay. Yield and ultimate shear strengths of degraded nailed timber joints could be estimated properly based on European yield theory by using measured strength values of lumber and wooden panels and in consideration of mass-loss and moisture content of wooden panels. However, nail-head-pull-through strength of MDFs was estimated as low because of its modified density and the reduction coefficient for high moisture content established by the current standard for structural design of timber structures in Japan.
