A comparative analysis of the resistance of tubular joints

The resistance of tubular joints is conventionally determined by the failure mode approach where strength formulae are often determined in a semi-empirical way. The European standard EN 1993-1-8 is under the revision with the goal to have a new version in 2020. The design equations for hollow section joints in Chapter 7 of EN 1993-1-8, which have been calibrated against available experimental results in the 80’s, are compared with the design formulae in the international standard ISO 14346. In ISO 14346, the design equations have been re-analysed, adopting the results of extensive numerical investigations initiated in the 90’s. Considering that a new version of EN 1993-1-8 is being drafted, which aims at adaptation of the newest generation of design equation for tubular joints, a comparative study between the codes have been performed. The results showed that a significant inconsistency exists between current EN 1993-1-8 and ISO 14346. The difference in strength prediction by the standards in some design situations reaches around 400%, e.g. for RHS T, Y and X joints with small β ratios and high compressive chord stress. A selection of available experimental and numerical results, in general, showed a better agreement with ISO 14346. The recently proposed amendments and corrigenda on EN 1993-1-8 Chapter 7, by a group headed by Prof. Wardenier and Prof. Puthli, minimize the identified differences with ISO 14346 yet they adapt most recent research outcomes for hollow section joints. Another proposed method, based on the component approach, is proved to be applicable to determination of the resistance of tubular joints. FE analyses preformed in this study confirmed the reduction of axial resistance of RHS X joints due to tensile axial chord stresses. Recommendations are given based on the numerical study on RHS full width T joints under in-plane bending moment with chords made of HSS.