Steel Beam (theoretical question)
Steel Beam (theoretical question)
(OP)
If an I beam is loaded uniformly along its span, the middle of the span is the position of maximum b.m. but zero shear. It is normally assumed that all the compressive stress is carried by the top flange, and all the tensile stress by the bottom flange. Assuming the load pattern never changed, would it be possible to cut a vertical slot down the web at the centre of the span,leaving only the top and bottom flanges intact? Theory seems to say 'yes',but somehow doesn't seem right to me.






RE: Steel Beam (theoretical question)
RE: Steel Beam (theoretical question)
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Steel Beam (theoretical question)
Found here: AISC Design Guide 2 link
RE: Steel Beam (theoretical question)
sure you could recalc I to remove the web contribution, and sure the change would be smallish, but not negligible (not clearly negligible).
and there's a small matter of stress concentration (the web would feel the cap tension stress (near enough). but if the loading never changes, there'd be no fatigue either ...
RE: Steel Beam (theoretical question)
RE: Steel Beam (theoretical question)
Actually, the two flanges will have considerable shear capacity. It is normally ignored when a web is present, but in this case it should be considered. The flanges are weak in bending, however.
This is an approximation sometimes made when trying to zero in on a beam size but, as stated by others, the web does carry a small portion of the bending moment.
With a vertical slot at midspan, secondary stresses would have to be considered, but it is quite true that the flanges alone could carry almost the full bending moment of the full section if the slot is not too wide.
BA