ABSTRACT
We study the Y-shaped joints using rectangular hollow sections, so called "bird-mouth" or "bill-shaped" joints. Experiments on local failure of such a joint subjected to out-of-plane bending moment were conducted. Two types of failure were observed as a result. One is the local failure of the chord near the joint and the other is the collapsing of the leg of the bracing by the bending. It is shown that the moment capacity for the former case can be estimated by using the punching shear model assuming the effective punching shear region of the chord member. This region is determined from the experimental results. In case the diameter ratio is small and the width-thickness ratio of the chord is large, these moment capacities of joint are equal to or greater than that of the conventional type joint of CHS and RHS, comparing with the moment capacity estimated by use of the design strength formulae proposed by CIDECT.
