FIELD FIX: Glitch in manufacturing Plate Girder
FIELD FIX: Glitch in manufacturing Plate Girder
(OP)
I'm working on a project where the wrong size plate was used for the web during the manufacture of some plate girder columns. These columns have already been fabricated and shipped to the jobsite.
Apart from all the acrimony and finger pointing that is sure to occur; I want to have understanding of the different options available to increase the shear carrying capcity of a plate girder.
In a case such as this, is it okay to include the flanges in computing the shear strength of the member? If so, how would the contribution of the flanges be calculated?
Any other ideas, suggestions or comments would be more than welcome.
Thanks.
JS.
Apart from all the acrimony and finger pointing that is sure to occur; I want to have understanding of the different options available to increase the shear carrying capcity of a plate girder.
In a case such as this, is it okay to include the flanges in computing the shear strength of the member? If so, how would the contribution of the flanges be calculated?
Any other ideas, suggestions or comments would be more than welcome.
Thanks.
JS.






RE: FIELD FIX: Glitch in manufacturing Plate Girder
RE: FIELD FIX: Glitch in manufacturing Plate Girder
I am assuming that you are using AISC specification for the girder design. It has been my experience that steel members are hardly governed by shear stress! Is the girder overstressed in shear with the thinner web plate? Are the flanges and web continuously welded or they have intermittent welds?
I recall in my early days in college, my steel professor did the shear calculations including the flange thicknesses as part of the shear carrying element for hot rolled sections. In other situations, he deducted the flange thicknesses for same hot rolled sections. I think it is a judgment call. You can argue for each method when using hot rolled sections.
What is the fv compared to Fv for the thinner web plate?
Regards,
Lutfi
RE: FIELD FIX: Glitch in manufacturing Plate Girder
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Regards,
Lutfi
RE: FIELD FIX: Glitch in manufacturing Plate Girder
Regards,
Lutfi
RE: FIELD FIX: Glitch in manufacturing Plate Girder
Your allowable bending moment will be reduced slightly as well.
In some cases, you could add stiffeners to the web to increase shear capacity- depends on what governed the design in the first place.
The design codes are always written in terms of minimum specified yield strength. Actual yield strength, as shown on mill test reports, will run several KSI higher. If it can be approved by all concerned (and that's a big IF), you could redo the design using actual yield or tensile strengths.
Who designed the beam? Get them involved if they're not. There may be some inherent overdesign included. They may can remove some approximations and reduce the required strength.
Depending on the configuration, you could possibly weld a strip of plate on the web, near one of the flanges. Fair bit of work, but better than scrapping the beam.
RE: FIELD FIX: Glitch in manufacturing Plate Girder
RE: FIELD FIX: Glitch in manufacturing Plate Girder
A little more background: due to space constraints, we were forced to use a shallower column than we normal and as a result, the thinner web plate does result in overstressing the member in shear.
The fv compared to the Fv is at a ratio of 1.6 overstress. Axial capacity is okay and even the reduced allowable bending moment is sufficient.
I did use AISC Allowable stress to design the beam based on Section F4 of the 9th Edition. However, looking at the commentary C-F4, it describes the shear yield stress as
Fy/(Sqroot 3).
My understanding is that this is the inelastic shear yield of the web plate. When can I use C-F4 to compute shear capacity?
Thanks for all your responses so far.
JS.
RE: FIELD FIX: Glitch in manufacturing Plate Girder