plate girder with corner angles

[serdardundar]

Hi,
I have seen a plate girder with 25m span, 80cm total height, 5cm X 60cm flanges, 2.5cm X 70cm web. And four corner angles of same dimensions are used at top and bottom of the web. The flanges are made up of 2 2.5cm thick plates which are bolted at certain intervals.... I wonder if the corner angles serve for anything (like connection of flange and the web plates) other than increasing the moment of
inertia of the I beam? I mean; can i use top and bottom cover plates at the place where i need them or use thicker flanges so that i do not need to use corner angles? Is there a problem with connecting the flange and web of the beam only with corner welds? Is there a way of calculation for determining when corner angles should be preffered
instead of thicker flanges?
Another thing that i should mention is that the plate girder is not riveted type girder. The angles are NOT riveted to flange or web. The angles are just welded to flange and the web along ends of their legs. So the flanges are connected to the web with corner welds and welds at the edges of angles.Would there be a problem if i don not use angles at the web - flange connection.
Thanks for your help....

 

[ishvaaag]

In my opinion, anything with angles there is a bit old design, were put there partly for constructability. If as per the present codes you see the girder would comply the applicable code, then you may omit them, I think.

 

[JAE]

Yes, per ishvaaag, here in the U.S. most steel bridge girders are constructed with a direct welded connection between the flanges and the web.

 

[anandaganesh]

This type of detail is used where the flange and web are connected by bolts through these angles. In welded construction this type is not used.
You can see this type of girders in old railway bridges.

This angle section will be subjected to longitudinal stresses and the horizontal
shear at the junction of web and flange.

 

[Rentapen]

Not only on old bridge plate girders, we still use clip angles to square the top and bottom flanges and perpendic with the web. Usually the stiffeners will do the trick but assembly is a lot easier with some clips for centering and then tacking. Sometimes we remove sometime not.
rentapen