Local buckling in class 2 continuous composite beams

For continuous composite beams, with type of cross-section as shown, the neutral axis is shifted towards the top flange, and in negative bending the joist is subjected mainly to compressive strains, from which the local buckling of the web and low flange limit its rotation capacity, therefore keeping it from reaching its ultimate strength. The work described in this paper is aimed at providing more information on local buckling and its effect on rotation capacity in the negative moment regions of continuous composite beams. An analytical design method based on a collapse mechanism is developed, allowing us to estimate, with sufficient precision, the rotation capacity of the central support as a function of bending. This method has been justified by experimental results (Aribert, J. M. and Raoul, J., Two full-scale tests of class 3 composite beams. Proceedings of Engineering Foundation Conference on Composite Construction, ASCE, Potosi, MI, 14-19 June 1992) and by its comparison with other methods proposed in the literature (Johnson, R. P. and Climenhaga, J. J., Moment-rotation curves for locally buckling beams. Journal of the Structural Division, ASCE, 1972, 98(ST6), 1239-1254; Johson, R. P. and Chen, S., Local buckling and moment redistribution in class 2 composite beams. Structural Engineering International,1991, April, 27-34). (C) 1997 Elsevier Science Ltd.