Wide Flange Beam - Web Yielding
Wide Flange Beam - Web Yielding
(OP)
I'm examining an A36 W12x26 that appears to have failed by web yielding. A W6x15 column, 10' long bears directly on flange of the W12. Web of the column and web of the W12 are in the same plane. The column did not buckle. Since the W12 had a pair of 1/4" x 3" full depth stiffeners at the column location, web crippling appears not to be an issue. Assuming "N" equals 6", I came up with 86 kips as the critical concentrated load for the beam web. However I have reason to believe that the load at failure was much higher. Assuming the stiffeners act as an "extra" web, with "N" equal to 6" and "k" equal to zero, come up with another 54 kips of capacity. Brings the total capacity to 140 kips at failure which seems to fit the conditions. All dimensions and calcs by AISC 9th Edition, ASD. Anyone see flaws in my logic (or arithmetic) or know a better way to analyse this situation? Thanks.






RE: Wide Flange Beam - Web Yielding
Could this be a new(er)50 KSI column installed on an older 36 KSI beam? If so, this might explain why the column did not fail but the beam did.
RE: Wide Flange Beam - Web Yielding
I did neglect to say that we do no know the applied load. Several dozen of similar W6 columns failed by buckling - when they buckled, the web and stiffeners of the W12 remained more or less intact. A few W6 columns did not buckle but failed anyway by destroying the web & stiffeners of the W12 as described. I'm trying to zero in on the loading that caused this combination of failures.
RE: Wide Flange Beam - Web Yielding
RE: Wide Flange Beam - Web Yielding
Just a possible variable in the puzzle.
RE: Wide Flange Beam - Web Yielding
If I remember my strengths of materials right, Euler Load:P(critical)=(pi)^2*(E)*(I)/(L^2)=185Kips (W6x15 @ 10')(AISC manual has factors of safety taken into account)
Are all the W6x15 posts supporting the same thing & framed together above the supporting W12s?
Base plates two bolt or four bolt?
If four bolt, are all in the same orientation (Webs Parallel to beam web? (four bolt in this condition would at least partially "fix" the base) If all are the same, this is moot.
Failure started somewhere. If there were more residual stresses due to the welding the stiffeners at this location than the others, it starts to fail first, the supporting framework above is now deflected, and instead of having a true axial load on the remaining W6x15 posts, you now have induced moment into them, (Ughh the dreaded P-delta), which would cause them to buckle more rapidly.
Just my 2 cents and thoughts, not knowing all the parameters
RE: Wide Flange Beam - Web Yielding
What we are trying to determine is the force necessary to have "squashed" the W12s at the end of the few columns that did not buckle. That force must have been less than the 159 kip to 185 kip range that would have caused the columns either to yield or buckle.