The Japanese Building Code provides formulas to calculate the buckling strength for structural lumber and structural wooden engineered products such as glulam and LVL. The adaptability of these formulas against cross laminated timbers is discuss in this paper. To determining the buckling strength properties for cross laminated timbers a series of buckling test were operated for full-size cross laminated timber of certain structural grades. The buckling loads obtained though these tests were compared to those derived from the formulas given in the Japanese Building Code. The measured buckling loads and the calculated buckling loads were almost equivalent. The result indicated that in general the formulas given in the Japanese Building Code can well evaluate the buckling strength of cross laminated timbers.
In the past study, we conducted compression tests with laminated veneer lumber of Japanese Larch. We observed the deflection and strain behaviour. As a result we could evaluate the bucking strength with Euler’s equation and Tetmajer’s method. For structural design we should expand the versatility of that method. Three wood species for structural members would be selected for these tests. Those were Japanese larch, Japanese cypress and Japanese cedar. For the test parameter, we set the 8types of slenderness ratio for the compression test and we conducted monotonic compression tests with pin-supported on both edges. For the mechanical properties we conducted compression tests with short column members and got yield compression for those materials. In the compression tests, we could see the bending deflection. We would get the ratio the maximum strength and yield strength for distinguish the limited slenderness ratio. As a result it was cleared that the limit slenderness ratio of these wood species was 100. And we could confirm that the Tetmajer’s method is useful for evaluation the yield strength.
Slender timber beams subjected to gravity loads may buckle in the out-of-plane direction. Normally, the same bracing system that is used to prevent lateral movements of the beams, caused by external transversal loading, also serve to increase the buckling strength of the beams. For the idealized case of a perfectly straight beam with full-bracing there is no force in the braces even at buckling because there is no displacement at the brace points. However, in real beams brace forces do develop during loading. This paper describes experimental and analytical studies performed on slender glulam beams subjected to gravity loads laterally stiffened by means of discrete bracing. In particular, the influence of relevant parameters such as i) brace stiffness, ii) brace position, iii) shape and magnitude of initial imperfections on the brace force were investigated.
