Existing Plate Girders
Existing Plate Girders
(OP)
I have a floor system consisting of concrete slab supported by old school steel plate girders. I've reverse engineered the girders, and have come up with rather large DL and LL capacities, almost like a factor of safety of 2. Am I missing something in my analysis? Is there a strength reduction for plate girders? I checked my section properties twice, and came up with the same results (thank god). I used 20 ksi for Fb.






RE: Existing Plate Girders
Additional reduction may be needed if it is hybrid girder, or the flange Fy differs from the web Fy.
Use WFbeam.exe at http:www.lanxun.com/pce to double check your work.
RE: Existing Plate Girders
RE: Existing Plate Girders
RE: Existing Plate Girders
How old are the plate girders? Do you know what type of steel was used in their fabrication? I think during the 1940's and maybe 1950's, steel had a yield strength of 33,000 psi, with a maximum allowable tensile stress of 18,000 psi. Also during that period welding electrodes were Series 60 (60,000 psi).
AEF
RE: Existing Plate Girders
I also read a quick note in an old text about a rivet reduction factor of 15%. Can anyone clarify this?
RE: Existing Plate Girders
Respect rivets, I have a spanish code on them, it would be easy to recalculate as long as the standing condition of the same would be determined. A 15% reduction on the shear capacity might be in relation with the fact of the rivets being upon cooling prestressed in an unknown amount (interaction) ...yet this should be directly accounted in any code values or procedure.
RE: Existing Plate Girders
A number of years ago I had to evaluate an existing built-up plate girder highway bridge on a small county road. I went to the local engineering library and found a series of structural books written in the 1920's by Hool and Kinne. They had worked examples of plate girder design and information on the types of steel in use at that time. The engineering calcs. are not the difficult, the real problem is to make some assesment of the material used in the the plate girder and its present condition. That is where your engineering judgement comes in.
Good luck!
RE: Existing Plate Girders
Good Luck.