For the materials of the brace member in bearing walls of Japanese wooden houses, sawn lumber, laminted veneer lumber (hereinafter called "LVL") et al would be used commonly. Those members would be needed to resist compression and tensile force. Under the compression load, those member would be reduced the strength depending on the geometry. This phenomenon would be called buckling, and the evaluation of buckling strength is very important in structural design.

In calculation of buckling strength, the Euler's method is famous and useful, so it is refered by some standard. For Standard for Structural Design in Japanese, we couldn't use that method directly, because timber material don't have the clear yield point. In our past study, we proposed a new method of evaluation method of buckling strengh, and evaluation method of yield strain from short-column compression tests. In this study, we would apply that method to LVL of Japanese Larch.

For the material, the wood species is Japanese Larch, the strength grade is 100E in Japanese Agricultural Standard(hereinafter called "JAS"), and the cross-section is 45×90 mm.

As a material tests, we conducted short-column compression tests and bending tests based on Japanese Agricultural Standard of plywood and LVL. We compared the yield strain from the both tests, and defined as a yield strain from short-column compression tests. The yield strain was almost 2400×10^{-6}.

Next we conducted compression tests with different length or different slenderness ratio with 50, 60, 79, 80, 100, 130, 150 and 190. From the compression tests we would get the some types of bucking strength, the one is the strength from southwell's method(σ_{1}), the second is the maximum stress(σ_{2}) and the last is yield buckling strength (σ_{3}). As compared the σ_{1} and σ_{2}, the both values would be almost the same.

When we compared the σ_{1} and σ_{3} with large slenderness ratio, both values are almots the same. On the other side we could clear difference in both value in small range of slenderness ratio. The border would be called "limit slenderness ratio" theoretically. Then we focused on the ratio (σ_{2}/σ_{3}), between the 50 and 80 of slenderness ratio, we could find a difference between σ_{2} and σ_{3}, and the ratio was bigger than 1.2. In the area from 80 to 190 of slenderss ratio, the ratio was almost 1.0. As a result, we could define the limit slenderss ratio was 80 in this study. In fact the elastic buckling occuered over 80 of slenderness ratio and the yield buckling occuered under 80 of slenderness ratio.

Finally we would apply the Euluer's method for the evaluation of elastic buckling, Tetmjer's method and for the yield buckling. Then we could get the lower limit strength with combination of both method. In this method, we used 5% lower limit value in JAS for the Young's modulus in Euler's method, experimental 5% limit strength for the strength in Tetmjer's method.