Parametric finite element study of branch plate-to-circular hollow section X-connections

The limit states design resistance of plate-to-hollow structural section connections subjected to branch plate axial load is generally relatively low, due to an imposed deformation limit of 3% of the connecting face width for rectangular hollow section (RHS) connections or 3% of the diameter for circular hollow section (CHS) connections (Lu et al. 1994, Wardenier et al. 2008a). Though a deformation limit is practical and necessary, the potential strength of the hollow section member is being under-utilized, particularly with the increase in use of heavily-loaded plate-tohollow structural section connections in tubular arch bridges and cable-stayed roofs. The need to develop a means to strengthen these connections becomes apparent. One method of strengthening these connections is to pass the branch plate through the chord member and weld the plate to both sides of the tube, producing a "through plate connection". Through plate-to-RHS connections have previously been studied (Kosteski & Packer 2003) and design recommendations have since been incorporated into CIDECT Design Guide No. 9 (Kurobane et al. 2004). However, design recommendations for through plateto-CHS connections have been absent in published literature, indicating the need for further research.