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PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
Edited by: B.H.V. Topping
Finite Element Modelling of Laser Welded Connections for Built-Up Cold-Formed Steel Beams
R. Landolfo1, F. Portioli1, O. Mammana1, G. Di Lorenzo2 and M.R. Guerrieri2
1Department of Constructions and Mathematical Methods in Architecture, University of Naples "Federico II", Italy
R. Landolfo, F. Portioli, O. Mammana, G. Di Lorenzo, M.R. Guerrieri, "Finite Element Modelling of Laser Welded Connections for Built-Up Cold-Formed Steel Beams", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 148, 2007. doi:10.4203/ccp.86.148
Keywords: finite element model, nonlinear springs, laser welds, cold-formed built-up members.
The numerical simulation of laser welds is a key aspect in the calibration of reliable finite element models of built-up members, especially when the ultimate strength of the elements is influenced by local buckling of compression parts between connections.
Different modeling approaches for welded connections can be found in literature. They are generally relevant to resistance spot welds and use solid or line elements for the simulation of connections. The first ones involve the use of brick elements and fine meshes at connection zones. Such methods are used to analyze in detail interactions between steel sheets and welded zones but in this case the computation becomes too much time consuming if the global response of whole structural members is investigated. The modelling of connection by line elements is suitable for developing finite element models of whole structural assemblies connected by spot welds. In this case a link or beam element is used for joining the steel sheets. These modeling approaches present some problems which are mainly related to the bending stiffness of the beams used for connection, which is coupled to translational degrees of freedom. As a consequence, secondary bending moments are transmitted to the plates at connection points causing early buckling phenomena in compression elements.
The approach proposed in this paper for simulating the laser welded connections is based on nonlinear spring elements. The elements were formulated independently for each direction by uncoupling the effect of shear and bending on the steel sheets.
The numerical model of connections was calibrated on the basis of several experimental tests carried out on single-lap laser welded specimens .
The finite element model of the lap-shear specimens was implemented using the ANSYS finite element software package. The SHELL181 element was used to model the laser welded sheets and COMBIN39 and BEAM188 elements were considered to develop the finite element model of laser welds.
The reliability of the model was validated against the results obtained from experimental tests performed on a full scale prototype of laser welded beam. In particular, an application to the numerical modeling of structural response relevant to the compression flange of a cold-formed built-up steel beam was shown.
The comparisons with experimental tests both in terms of ultimate load and buckling shape showed the effectiveness and the practical use of the proposed approach for finite element modeling of laser welds.
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