Finite element modelling procedures for innovative built-up cold-formed beams: Fid-Bau Portal

Finite element modelling procedures for innovative built-up cold-formed beams

Landolfo, Raffaele / Portioli, Francesco / Lorenzo, Gianmaria di

The patented MLC Beam is obtained by assembling two special cold-formed C-profiles, so that a double-T symmetrical cross section with hollow flanges is formed. The two profiles are jointed each other through mechanical fasteners distributed on the web and on the flanges of the beam. Two reinforcing plates are placed inside the top and bottom hollow flanges of the double-T shapes, which provide a flange connection system between the two C-profiles. In the present paper, the first numerical results concerning the simulation of the bending behaviour of the built-up steel member are presented. Both connecting systems and contact interactions have been considered in the FE model, and an alternative method for applying geometric imperfections has been proposed. Such method consists in assigning an initial imperfection equal to the buckling mode obtained from the non linear analysis carried out on the perfect geometry. In this way, the inelastic buckling mode can take into account the contact interactions between the different parts of the beams. The numerical model has allowed the failure mechanisms of the investigated beam to be interpreted. In particular, it has been shown that the member collapses when both the web and reinforcing plate buckling occur for the compressive stresses caused by bending. The first numerical analyses carried out on the member with and without local imperfections have shown a remarkable sensitivity of the model in terms of load bearing capacity, which can be reduced up to 5% with respect to the ultimate load of the member with perfect geometry.