Stability, Failure and Design of I-Section Steel Beams Subjected to Tension

This paper reports the results of an analytical, numerical and experimental investigation dealing with I-section steel members acted by a combination of major-axis bending and axial (“beams subjected to tension”), which is relatively rare in practice and, therefore, has received little attention in the past. In particular, there are no guidelines for the design against buckling ultimate limit states of such members (only their cross-section resistance is checked). This means that the axial tension favorable effect on lateral-torsional buckling/failure is neglected, leading to over-conservative designs − indeed, a beam subjected to axial tension is currently designed against lateral-torsional failure as a “pure beam”. In order acquire scientific knowledge and provide design guidance on this topic, the lateral-torsional stability, failure and design of hot-rolled steel I-beams with fork-type end supports and acted by simple transverse loadings (mostly applied end moments) and various axial tension values are addressed in this work. After developing and validating an analytical expression to calculate critical buckling moments of beams under uniform bending and axial tension, beam finite element buckling results are presented for the non-uniform bending cases. Then, two full-scale tests involving a narrow and a wide flange beam under eccentric tension are described and their results are used to develop finite element models, subsequently employed to perform a parametric study aimed at gathering a fairly extensive ultimate strength/moment data bank. Finally, this data bank is used to assess the merits of a design approach proposed here for beams subjected to tension and collapsing in lateral-torsional modes − this design approach, which consists of slightly modifying the current procedure prescribed in Eurocode 3 to design beams against lateral-torsional failures, is shown to provide ultimate moment estimates that correlate very well with the values obtained from the numerical simulations. 

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