You really need to calculate it for yourself since you don't seem to believe me.
If you have any idea of how to analyze the stress on a weld you should be able to do it with the information on this site
http://www.roymech.co.uk/Useful_Tables/Form/Weld_strength.html
Bear in mind that there were 5/16" fillet welds on both sides of the 18" height of the 3/4" thick stiffener at the web and 3/8" fillet welds on both sides of the 5.485" width of the stiffener at the flange, as shown on Frankel Steel drawing 9114.
The floor loads on the girder would have been about 50% of the 45 x 53 foot area east of it and about 25% of the similar sized area west of it. One end of the girder handled half of that load. So you can use 37.5% of the 45 x 53 foot area and a floor load of 125 psf maximum for the load on that end of the girder.
I am sure you will find that the stiffener design was more than sufficient to keep the flange from failing if the web was not over the seat.
I'll give you a hint: The resultant stress on the welds at the web from the combined vertical shear and bending would have been less than 8,000 psi. E70 weld metal can take 70,000 psi, and the parent material had a tensile yield strength of about 42,000 psi. Shear yield strength of a ductile material is about 57.7% of tensile yield strength, so the parent material wouldn't have sheared at less than about 24,000 psi and the stress there would have been a little less than 8,000 psi as the shear area is a little larger on the leg of the fillet vs. the throat (which is used for the weld).