Lomarandil
Structural
- Jun 10, 2014
- 1,912
Just wanted to bounce an idea off some of the members here to see if it sticks.
I deal with old built-up girders a lot -- fabricated prior to any of the AASHTO codes, let alone those with the proportions limits in the current code. Typically we're talking about 30 ksi A7 steel, riveted girders with a web plate, flange angles, and cover plates for some portion of the girder length.
It's not uncommon for these girders to have very non-compact webs (2Dc/tw>220). This means that there's often a pretty substantial hit in web-bend buckling capacity Fcrw.
Now, I understand that the web bend buckling check is designed to limit compressive stress in the portion of the web contributing the flexural compression. But -- if web bend buckling is a stable buckling mode (per the commentary) and would be restrained by other elements (e.g. transverse stiffener angles at regular spacing) -- would it make sense to throw out the web bend buckling limit as long as the section checked out for other limit states when section properties (Sx) are computed based only on the flanges?
Or am I missing something in the bigger picture?
Thanks!
I deal with old built-up girders a lot -- fabricated prior to any of the AASHTO codes, let alone those with the proportions limits in the current code. Typically we're talking about 30 ksi A7 steel, riveted girders with a web plate, flange angles, and cover plates for some portion of the girder length.
It's not uncommon for these girders to have very non-compact webs (2Dc/tw>220). This means that there's often a pretty substantial hit in web-bend buckling capacity Fcrw.
Now, I understand that the web bend buckling check is designed to limit compressive stress in the portion of the web contributing the flexural compression. But -- if web bend buckling is a stable buckling mode (per the commentary) and would be restrained by other elements (e.g. transverse stiffener angles at regular spacing) -- would it make sense to throw out the web bend buckling limit as long as the section checked out for other limit states when section properties (Sx) are computed based only on the flanges?
Or am I missing something in the bigger picture?
Thanks!
