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.

 

[hoshang]

3. Roof Dead and Live Load.

Roof dead load= 1kN/m2
Roof live load=1kN/m2

First Floor Dead and Live Load. 30 cm seems very thick for a floor slab. Is it correct?

First floor dead load=-3kN/m2
First floor live load=-3kN/m2
for slab thickness, please read the original post. The slab thickness is 15cm.

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)

My reply is:

I believe you indicated that the steel structure has been completed and the First Floor slab has been poured.

7. You are proposing a new HEA addition to the column. Is that even possible if steel erection is complete?

I thought reshoring the beam and slab, removing bolts, and then welding the HEA to the existing column may be a solution.

8. What will the HEA bear on? Need foundation detail.

Please find the attached file.

 

[r13]

hoshang,

Seems this thread is getting too long, but the solution (that satisfy you) is yet to be found. Why not to open a new thread (with title changed) with sufficient information as example shown below, for ease of understanding, and pinpoint your concerns. (Note M (capacity) in example below means the actual moment capacity of the detail afford, which is less than the moment in demand, expressed as M (required))

Note that meaningful diagrams draw attentions, not the worksheet, which is difficult to digest, and I doubt anybody would ever go through it.

 

[BAretired]

The original drawings show the column webs running N-S, parallel to the beams. The foundation plan shows column webs running E-W, perpendicular to the beams, although it may be open to interpretation.

Floor and Roof beams can be made continuous through the south columns by continuing the beam flanges through each column, using plates welded within the column. Column orientation is needed in order to prepare a suitable detail.

If the column section still needs strengthening, plates or angles could be welded to Column C1 where required. The proposed HEA addition should be avoided if possible.

BA

 

[r13]

I guess the building has been built, or under construction.

 

[hoshang]

Floor and Roof beams can be made continuous through the south columns by continuing the beam flanges through each column, using plates welded within the column. Column orientation is needed in order to prepare a suitable detail.

Thanks. Can you elaborate this more.

If the column section still needs strengthening, plates or angles could be welded to Column C1 where required. The proposed HEA addition should be avoided if possible.

Will plates or angles solve the required moment? My thought is that plates or angles will provide for axial load.

 

[BAretired]

Sure I can elaborate on this. Provide and weld horizontal plates within the column of the same size as the beam flange. See the Enlarged Joint Detail by r13 above. That works if the webs are parallel to the beams.

You need to confirm which way the C1 columns are oriented. Are the webs parallel to the beams or perpendicular? Your Foundation Plan shows a single web running East-West in the foundation detail, contrary to your earlier drawings. The Foundation Plan itself seems to indicate two webs running East-West. Kindly clarify.

You also need to provide some dimensions. See the question marks below.

BA

 

[hoshang]

You need to confirm which way the C1 columns are oriented.

The web of the column is (from north to south on plan).
Thanks for the elaboration.
Question marks:
Longer dimension: 6.95m
Cantilever above: 2.5m

Your Foundation Plan shows a single web running East-West in the foundation detail, contrary to your earlier drawings. The Foundation Plan itself seems to indicate two webs running East-West. Kindly clarify.

Sorry, I'm not sure what you mean.

 

[BAretired]

The web of the column is (from north to south on plan).

If that is true, then your earliest drawings were correct, but your Foundation detail is wrong as it shows the web of all C1 columns running East to West. Do you have a revised Foundation Plan showing the correct orientation of Column C1?

You have not included a First Floor Framing Plan in your submission. If you have one, it would be helpful.

If C1 is oriented so that the typical beams are framing into the flange of the column, then the space between the column flanges is congested, particularly if there exists a beam framing into the web of the column along the exterior gridlines. This would make it difficult to extend the beam flanges through the column as shown on r13's sketch because the beam would be in the way.





BA

 

[BAretired]

Quote (BAretired)
Your Foundation Plan shows a single web running East-West in the foundation detail, contrary to your earlier drawings. The Foundation Plan itself seems to indicate two webs running East-West. Kindly clarify.

Sorry, I'm not sure what you mean.

I mean that a blowup of Column C1 on the Roof Framing Plan looks like the sketch below. Similar on Foundation Plan, but the detail on the Foundation Plan indicates a single web running East-West. To me, that looks like two webs running East to West. It looks like double wide-flange members meeting together at the flange tips. What you are telling me is not consistent with the drawings you are posting.

BA

 

[hoshang]

Hi BAretired
Thanks. As I stated in OP my friend asked me to check his project. So these pictures are his own. I took some pictures. Please find the attached file.

 

[hoshang]

Yes, you are right about congestion

 

[Agent666]

Honestly, worst welding I think I've ever seen. I'd look into this as well.

The end gap on the end plate is also scary. Clearly the bolts have not been tensioned correctly.

 

[BAretired]

BA

 

[BAretired]

BA

 

[hoshang]

Thanks BAretired. Sorry, but these columns are the three interior columns (therir webs are from east to west). Find the attached file for the exterior columns (their webs are from north to south).

 

[r13]

If this connection is the problem, I would add cap plate and stiffener plate as shown. Note you should make sure the the column is adequate for the local effects.

 

[BAretired]

r13,
I believe your suggestion has merit, but the 'cap plate' is really a tension plate and the upper bolts do not look very reliable as shown. This photo was taken before the slab was poured, so the bolts may have been tightened after the photo was taken. In any event,it might be a good idea to weld the end plate of the beam to the column flange, if that is possible.

There will be some overhead welding involved with this remedial work. The quality of welding has to be improved substantially. It may be that r13's cap plate has to be extended to the left, lowered and welded to the web of the E-W beam. The right end should align with the top flange of the N-S beam. The intent is to provide the equivalent of a through plate within the column.

BA

 

[BAretired]

Thanks BAretired. Sorry, but these columns are the three interior columns (therir webs are from east to west). Find the attached file for the exterior columns (their webs are from north to south).

Okay hoshang. Below are the files I have received to date. I do not have a Floor Framing Plan and would like to see one if possible. Also, there should be a modified Foundation Plan showing the correct orientation of all columns. I would like that too, if possible.

BA

 

[r13]

BA,

Agreed, extending the cap plate to the beam will be a great improvement.

 

[Agent666]

Stiffeners won't fix the original root issue with the column flange not having sufficient capacity to resist the local bending from bolt tension forces. It may improve things a little, but it was failing by a lot.

The welding potentially severely compromises the lateral and gravity load paths, I'd be very concerned about that. Not that framing into the web with the clip angles really creates a whole lot of continuity or lateral load path in the first place, but I fail to see what the load path might otherwise be for lateral loads based on the information given to date.

Hoshang, it would be useful to know what you intend to do about the welding, without that being addressed it seems like the structure is in a very compromised state. You have not explained the history of how you got to where you are, apart from it's a friends structure. As we ask more questions we simply find out more things that could be potential issues, I'm sure there are probably more issues that have not been discovered yet based on what we have been drip feed. You'd have to step back and ask if its worth retaining what has been built or replacing, as you've discovered design issues, construction issues and who knows what else is still to come. If you're in over your head on this one, perhaps it's time to seek the advice of other local engineers.

Being reliant on some folks on the internet to solve and discover a multitude of serious issues is probably not the most efficient approach. I appreciate there are probably some language barrier issues here, but if you look back on the thread, getting what seems like simple information to answers has been a bit painful...

I'm curious what country this is in given you originally noted design to Eurocode, then checks to AISC being acceptable?