Abstract
Generally steel portal frames carry vertical load, for instance of dead load and snow load on the roof, and horizontal load, for instance of earthquake and wind. Then bending moment of the members grow bigger at corner crossed beam and column, result in strengh of whole frame is almost fixed by rigidity of the corner knee members. Especially in case of truss structure of that rigidity out of loading plane is extiemely weak compared with rigidity in plane, how to brace the truss members become the most important point. In effect truss structures have certainly bracing members (for instance of purins and furring strips) at the outer cord member, but at the inner cord member often no bracing members. Then if the inner cord member carries compressive axial load, it is in danger of laterally jumping out before attaining to prearranged strength. Truss member of large depth come into question of influence on strength and differection by bracing members, and whether the bracing member at the outer cord member take effect for jumping out of inner cord member. For explaining these question, we made an experiment on lateral buckling of knee members of truss structure composed by angle and pipe sections.
