Connections of double branch plates to circular hollow sections under axial loads

Circular hollow sections (CHS) are widely used in modern structures because of their lightweight and aesthetic appearance. CHS can be found as a truss chord receiving connections from other branch members. Literature is rich with research on the behavior of connections using a single branch plate (SBP). Also, design rules are available in international codes to calculate the capacity of this type of connection, depending on the branch plate orientation and the type of loads transmitted to the chord. Few studies have been conducted on the connection with double branch plates (DBP) to rectangular or square hollow sections, aiming to enhance the connection behavior and increase its capacity; however, it is still not studied for CHS and is not covered in the design codes. This paper investigates the behavior of longitudinal DBP under axial load to the CHS chord in a T-joint. For this study, a nonlinear finite element analysis is performed using ABAQUS software. The geometry of the DBP in terms of plate thickness, length, and spacing are studied. The results are compared to the available design rules for connections having SBP. The failure modes are presented, and the effects of the different parameters are studied. The paper ends with a proposal to calculate the capacity of longitudinal DBP, showing a greater capacity than the common SBP.