Weakest component: COLUMN FLANGE - TENSION

[hoshang]

Hi
My friend asked me to check connections in his project according to:
Design of fixed beam-to-column connection
EN 1993-1-8:2005/AC:2009
I noticed that one column has weakest component at column tension. The project is under construction and the steel frame is installed. Please find the attached files.
How this can be fixed? I thought of adding stiffeners & brackets, this helped but not much. I noticed a diagonal crack on top of the RC slab projecting from this column for about 15cm.

 

[Agent666]

I'd assumed they would have been tensioned, so you shouldn't retension them as you'd risk fracturing the bolts (my own code precludes this as, tensioning puts, the bolts past their yield point causing permanent elongation). Maybe they are also not long enough if you're adding backing plates.

 

[hoshang]

Hi
I found that the column section is not verified. Please find the attached file. My thought is adding HEA200 to the existing IPE360 according to following:
Longitudinal IPE360 + Transverse HEA200.
So the x axis of IPE is perpendicular to x axis of HEA
I appreciate any other thoughts.

 

[Agent666]

I honestly have no idea what you are now trying to say/do in your last post. Some sort of strengthening of the columns as they have not been designed as well?

Best if you provide an annotated sketch showing what you're proposing. Then your text description might make a bit more sense?

I thought the design was being done to Eurocodes, but this latest check is to AISC?

 

[hoshang]

Best if you provide an annotated sketch showing what you're proposing. Then your text description might make a bit more sense?

Please find the attached file.

I thought the design was being done to Eurocodes, but this latest check is to AISC?

Thanks. The sections are European Section. I haven't studied Eurocodes. So I checked the design with AISC.

 

[Agent666]

For some reason the file does not download. Try again with a different name.

 

[hoshang]

Hi
Please find the attached file.

 

[Agent666]

I thought you were posting a sketch to show what you were trying to explain. You just posted the same word file as previous with the AISC design?

 

[hoshang]

Hi
Sorry. Please find the attached file

Is the new HEA addition considered as reinforcement for the column?

 

[hoshang]

I thought you were posting a sketch to show what you were trying to explain. You just posted the same word file as previous with the AISC design?

I've attached the correct picture.

 

[Agent666]

Yeah might work. Provided you connected them together in some appropriate way.

A lot of work though and probably significantly stiffens the frames (so update the lateral analysis). You might also need to consider all of the dead load is already in the current columns, so new addition might not carry any axial loads.

 

[hoshang]

Yeah might work. Provided you connected them together in some appropriate way.

Which section of AISC should I use to connect them together in some appropriate way?

A lot of work though and probably significantly stiffens the frames (so update the lateral analysis).

Sorry. Can you elaborate this more?

 

[hoshang]

Hi
The problem is that the column is getting a moment (Mry) greater than the available moment (FibMny) as shown in attached file on 16 Dec 20 17:51. How this column could be reinforced to resist this moment?

 

[BAretired]

Are you proposing an additional column for the full height of the structure or just the lower story? I understand the steel structure has been built and the floor poured, so it is not clear how an additional two-tier column could be installed; and it is not clear how a one-tier column could help with the moment.

Perhaps the existing column could be reinforced with plates, field welded in place. Please provide a sketch showing the moment and axial load diagrams.

Also, please confirm the design loads, including dead load, live load and wind load. Are there seismic events in your area?

BA

 

[hoshang]

Please provide a sketch showing the moment and axial load diagrams.

Thanks. Please find the attached file.

 

[Agent666]

Sorry. Can you elaborate this more?

If you are stiffening the frame and it is subject to seismic loading then you are changing its response and potentially also the seismic loads it must resist.

Stiffening the frame by a factor of 2 times, might simply increase the seismic loads and hence moments by a factor of 2. You need to follow through and reanalyse accordingly, I have no idea how this ratio might pan out. But sometimes you chase your tail, making it stiffer, but design actions go up accordingly.

Either way under gravity you potentially have a different distribution of design actions due to any stiffening of the columns relative to the beams, again you need to follow the changes proposed through in the design.

Which section of AISC should I use to connect them together in some appropriate way?

I don't use AISC, so maybe someone else could help/suggest any relevant code clauses. I suggest answering BARetired queries on the exact extent of the columns and how you intend to connect them as well, as theres a lot of missing information which we are otherwise guessing at. There is still a few outstanding questions earlier in the thread that have not been responded to.

I had perhaps made the assumption they would somehow be welded to the original columns, so you would use shear flow to design the welds typically in that scenario (i.e. from first principals, not from any specific code equation probably).

 

[hoshang]

I suggest answering BARetired queries on the exact extent of the columns and how you intend to connect them as well, as theres a lot of missing information which we are otherwise guessing at. There is still a few outstanding questions earlier in the thread that have not been responded to.

Thanks. I attached many information in earlier posts. Which else information you need? I'm ready to post other info. I'm seeking solution for the problem.

 

[BAretired]

I have marked up your drawing with a few comments. I believe you indicated that the steel structure has been completed and the First Floor slab has been poured.

The following items are needed in order to make sensible recommendations:

1. Plan Dimensions
2. Plan labelled "Floor" should be Roof Framing Plan? Please confirm.
3. Roof Dead and Live Load.
4. First Floor Dead and Live Load. 30 cm seems very thick for a floor slab. Is it correct?
5. Is it possible to continue the Roof Beam over the column?
6. Is it possible to continue the Floor Beam over the column? (possibly with welded plates within the column)
7. You are proposing a new HEA addition to the column. Is that even possible if steel erection is complete?
8. What will the HEA bear on? Need foundation detail.

Looking forward to hearing your response to the above.

BA

 

[hoshang]

The following items are needed in order to make sensible recommendations:

1. Plan Dimensions

Thanks. Please find the attached files.

 

[hoshang]

Roof framing plan

 

[hoshang]

Detail for column bearing