Flange Removal
Flange Removal
(OP)
I have a simple question over an ongoing office debate. Picture a column with 5" x 0.25" flanges and a 10" web. If the tension flange was removed and 2 2.5" x 0.25" plates welded to both sides of the web approximately 1" from the web end with 3/16" fillet welds, on the surface you would have similar section properties to the original column. I believe that in reality you would only have a stiffened T-section and the column would be subject to failure when loaded in bending. Please help with this office debate and if you have any good examples or references to prove your opinion, please let me know.
RE: Flange Removal
If the modification is localised then the designer must ensure the adequate transfer of the flange forces. Provided the details are suitable at the change from “proper” flange to the “replacement” flange, then my feeling is that you have close to the original section capacity.
We have modified a lot of columns, mainly using flange doubler plates or beam tees to make a cruciform section, and these have been assumed to contribute to the overall section.
If the existing column is in situ at the time of the modification, then the "tee" section will have some existing stress state. Perhaps the additional flanges (or other additional stiffening elements) don’t contribute to resisting this stress state, however, as the column become more heavily loaded and approaches the ultimate limit state my feeling is that the combined section will be effective.
What is your technical rationale for assuming the replacement flange does not contribute to axial capacity or bending capacity?
RE: Flange Removal
RE: Flange Removal
RE: Flange Removal
RE: Flange Removal
RE: Flange Removal
Calculate the shear flow at the web/flange interface as follows:
v = V x Q / I
v = longitudinal shear flow
V = shear force
Q = first moment of area of flange about neutral axis
I = second moment of area of section
Thus the flange, whether connected continuously by fillet weld or discretely by bolts or rivets, can be effective if the connecting elements can adequately transfer the shear flow. Consider the design of plate girders as an example.
Get out your university textbooks or search the Internet if you need to read more about shear flow.