huangyhg

tension flange buckling
does anyone know where to look for provisions on checking the tension flange of an i-section for buckling when the flange has been reduced. i am analyzing a beam that has a notch taken out of the tension flange.
thanks
i don't think you need to worry about buckling. however, you need to check fracture of the net section.
i won't have called it buckling either , but check the bending stresses in the flange (as the flange load goes around the notch).
the notch will increase stresses in the compression flange as well as the tension flange. i'm not sure the code provides a means for dealing with the increased tendency for the compression flange to buckle, so i would check the compression flange for buckling as though the whole beam was reduced in cross section.
i did project on this on this a few years ago. basically you have a non-prismatic beam which changes from symmetrical to asymetrical at the notch in the flange.
in my tests there was a notch in both the tension and compression flange. because the notch is on one side only, the resultant force in each flange is offset from the centreline. this results in a torsion effect in the beam and also moments in the plane of the flanges. all of this increases the onset of lateral torsional buckling. unfortunately, my project was limited to a qualitative study of the beam behaviour and i didn't get to develop any quatitative theory, sorry.
during testing, all beams (with various size of notch) started to twist at the onset of loading.
however in my testing, i did use one beam with a notch on both sides of each flange i.e. the reduced section remains symmetrical. this was to back up my theory of the offset resultants in the flanges - this beam did not twist at the onset, but did eventually twist and buckle at a higher load, as the resultant forces in the flange remained in line.
anyway my conclusion was that if this situation were to occur in practice, it would be best to restrain the flange if possible. otherwise the beam would have to be designed for bending and torsion combined (as i said earlier quantifying the torsion was not in the scope of the project).
i referred to a lot of work by nicholas trahair on non-prismatic beams and beams with initial curvature.

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