Abstract
Directly connecting beams to a CHS (circular hollow section) column without diaphragms in a moment-resisting frame, the CHS is partially thickened at the connection to prevent local failure and excessive out-of-plane deformation. In such a case, marginal length of the thickened wall beyond the outer surface of the beam flange is crucial to the strength and stiffness of the connection, which was experimentally and numerically investigated in this study. Increasing the marginal length of the thicker CHS accommodating flange plates, outer of which is butt-jointed to a thinner CHS, strength and stiffness obviously increase and approach to those for sufficiently large margin. The rate of convergence of the strength and stiffness with increasing margin is presented in a simple formula for design practice.
