Advancing utilization of domestic timber such as Sugi (Cryptomeria japonica), Hinoki(Chamaecyparis obtusa), Karamatsu (Larix leptolepis) is important from an environmental standpoint. As log construction was supposed to be applied to a retaining wall of a wharf, the mechanical properties of the elements were investigated by loading tests in this study.
　In the tests, two points loading was applied to continuous beams with two spans supported on crossing parts with notches. Machine rounded timber beams (species: Karamatsu) with the diameter of 10cm were used. The ratio a/d, where a is the distance between a loading point and a crossing part and d is the diameter, was varied from 2.0 to 5.0.
　As the results of the tests, the ratio R/P, where R is the reaction force at the center of the beam and P is the load, was 0.574 on average for all the beams at the peak loads. This value was 83.5% of the calculated value assuming simple supports. The ratio R/P was considered to be reduced by combined effects of initial inaccuracy, embedment, spring deformation of the crossing parts, and shear deformation of the beams. The ultimate bending stress was 38.7 - 62.7 N/mm2, that was 2.2 - 3.5 times as much as the standard characteristic bending strength, and the ultimate shear stress was 6.7 - 7.5N/mm2, that was 3.9 - 4.4 times as much as the standard characteristic shear strength. It implies that stress concentration does not reduce strengths when the direction of the load is perpendicular to the depth of notches.