Keywords: minor-axis beam-to column joints, finite element analysis.

The rotational behaviour of minor axis steel joints is in most cases governed by the deformation of the column web in transverse bending. According to Eurocode 3, these joints may be characterised only if loaded by equal moments on both sides of the web, therefore not activated in bending, as the column web deformed in bending is not covered by EC3.

A finite element analysis of minor axis joints is described, covering different configurations, varying the column web thickness and height, the end plate thickness and the bolt diameter, with special emphasis on the column web behaviour. The numerical results are compared to the analytical results from existing models: the Gomes model [1], for the prediction of the plastic moment, that is based on plastic analysis, and the Neves model [2,3] for the prediction of the initial stiffness, that assumes a numerically and experimentally validated unidirectional behaviour of the column web, trough a one-way spanning strip model.

The numerical models were grouped in three categories according to increasing column web slenderness: class 1 for low column web slenderness (up to 20), class 2 for medium slenderness (from 20 to 30) and class 3 for large slenderness (over 30).

Both class 2 and class 3 models show a behaviour governed by the column web compared to the other joint components. Nevertheless, for models with low column web slenderness (class 1), this contribution was not so dominant.

For the initial stiffness, numerical and analytical results from [2] and [3] presented a reasonable agreement, with an error smaller than 20%.

The plastic moment results obtained from the analytical model proposed in [1] showed, for the class 2 and 3 numerical models, both of them with the theoretical web plastic moment resistance as the governing factor, a reasonable approximation to the part of the moment-rotation curve corresponding to the onset of a horizontal or quite smaller stiffness. Nevertheless, for class 1 numerical models, this comparison is not adequate, since the moment capacity was governed by other joint components (bolts and end plate).

1

Gomes, F.C.T., Jaspart, J.P., Maquoi, R., "Moment Capacity of Beam-to-Column Minor-Axis Joints", in "Proceedings of the IABSE Colloquium on Semi-rigid Structural Connections", Istanbul, Turkey, p. 319-326, 1996.

2

Neves, L.F.C., Silva, L.S., Vellasco, P.C.G.S., "A model for predicting the stiffness of beam to concrete filled column and minor axis joints under static monotonic loading", in "Proceedings of Eurosteel 2005 - 4th European Conference on Steel Structures", Maastrich, The Netherlands, 2005 (in print).

3

Neves, L.F.C. "Monotonic and Cyclic Behaviour of Minor-Axis and Hollow Section Joints in Steel and Composite Structures". PhD. Thesis, University of Coimbra, Coimbra, Portugal, 2004, (in Portuguese).

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