FEM analysis of conventional and square bird-beak SHS joint subject to in-plane bending moment — experimental study

This paper presents the results of an experimental study of square hollow section joints subject to in-plane bending moment. A theoretical model of an XX-type traditional joint and the same one with the chord rotated through 45∘ about its longitudinal axis is considered. Models are analysed with the Finite Element Method and the results are compared with those obtained from the experimental study. The geometry, the material and the overall parameters concerned are in agreement with the general requirements of the EC3. A classification of joints due to their stiffness and M–φM–φ diagram is examined according to the last CIDECT guide No. 9 and Part 1.8 of EC3. The results showed that EC3 underestimates the design resistance of the conventional joints about 50%–70% and joints with β→0.5β→0.5 according to the rotational stiffness are classified almost as pinned while those with β→1.0β→1.0 react as semi-rigid connections.Chord orientation showed that has a very important effect in joints with β<0.85β<0.85 and increases their strength up to double when β→0.50β→0.50. In this same area for ratio ββ, connections react as rigid while for β→1.0β→1.0 they have strength almost equal to the conventional ones and behave as semi-rigid connections.