Column flange modification

[apsix]

Is there any merit in the modification as shown in the attachment?

The detail is one that I've inherited and it's been used before, but I don't like it.

We are required provide additional clearance for new equipment adjacent to the column, hence the cut-out.

It appears to me that the angle of the transition pieces is too acute to be an effective detail.

 

[csd72]

Where do the flange loads go? Follow your load path and all will be answered.

 

[civilperson]

The end plates are 2" thick and welded to both the flange and the transition plate. How will axial compression loads, (or axial tension loads), get from the flange to the transition plate through a right angle turn? Adding stiffener plates at right angles to the end plate and the flange/transition plate may allow the forces to go by the cut out.

 

[apsix]

Thanks.
Your thoughts echo mine, I was just wondering if I had missed something.
We now need to explain to the client why the detail issued 8 years ago is not good.

 

[civilperson]

The end plate will flex and by bending transfer the load to the changed orientation plate. This is hard to model since the beam distance varies along the end plate. Also the cut out becomes a stress concentration location for the shear between the two flanges. Add a web thickening plate as well.

 

[kslee1000]

It is interesting to see both units (mm, in) in a same sketch. Anyway, knowing this is a very unpleasant detail, have you looked into the reason(s) that it has stood for 8 years? I think your client might have the same question in mind.

 

[apsix]

kslee1000

We are still at proposal stage. It may be that the loads are so small that the detail does work anyway, despite its inefficency.
Also it's almost certain that the column hasn't seen full wind and crane loading.

 

[kslee1000]

Thanks for the response. Now you may have sensed that the column was either over designed, or loads have been reduced. These realizations could help you for the subsequent works.

 

[rb1957]

you gotta be carefull with that ... just because it's stood for 8 years doesn't mean that it's strong enough.

of course, it's a nasty looking detail, but is it understrength to the standards at the time ?

as always you've got to worry about the spin the lawyers will put on it ... particularly since someone has stuck their nose into it !? and now there's a electronic history of it too ...

 

[csd72]

what happens to the flage loads at the corners, the resultant of the two forces results in bending of the flanges.

 

[kslee1000]

In several occasions, I have encountered severely deformed/defective steel beams/columns in industrial buildings that, at first glance, all go-against engineering principles, and believes. After losing some hairs, some lessons are learned:

1. The loads on the defective element have redistributed to more stiffer elements/areas through frame action (over stress could occur somewhere away from this element, and its connections).
2. The real loads is much smaller than that in the original design.
3. Loading condition has changed, especially in industrial buildings, for instance - the newer equipment is lighter than it has replaced, change of use, fewer workers (due to plant modernization, layoff ...

Each event has its own set of conditions, that require prudent evaluation and understanding in order to provide better solution to the task at hand, and to satisfy curious minds.

 

[apsix]

"but is it understrength to the standards at the time ?"

To me it violates the principles of good engineering. The only thing that can save it is a low level of loading.

 

[kslee1000]

Good engineering is not afraid to ask why, to observe and to understand the odds before jump into conclusion. Otherwise, we are only a bunch of codified technicians.