Building geometry 10

[hoshang]

Hi all,
Please find the attached image.
Do you think the proposed geometry acceptable regarding center of mass and center of rigidity considerations? FYI the red circle is the center of mass.

 

[BAretired]

Do you intend to provide a Transfer slab for the Second Floor?
If so, should the Transfer slab be of uniform thickness throughout the First floor area? How much thick this Transfer slab should be to accommodate the planting of the new proposed columns? Do you have a detail for such planting of new columns in a Transfer slab?
Can the skewed columns be made of regular columns (rather than skewed)? Or circular columns?

Not a transfer slab...a transfer structure. The slab does not carry any columns; it just spans between beams. The slab should be adequate for the live load; minimum 150mm thick. All new columns should bear on a beam. No special detail is required, just starter dowels from beam into column. Each new column can be any shape you wish. They must only be in accordance with the code.

Ideally, the transfer level should have been First Floor, but a Show Hall at that level does not permit a forest of columns. That is why the Second Floor is selected as the transfer level, but support for the end of the cantilever can be shared by First and Second Floor, so one could say that both First and Second Floors are transfer levels.

 

[BAretired]

If we can do this, it would help a lot, both architecturally and structurally.

 

[rb1957]

the North (inclined) and South walls would be heavily windowed, no? same with the "light boxes" in the middle of the floor)

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[BAretired]

The North and South walls could be very heavily windowed, but I would like to get rid of the "lightboxes" in the middle of the floor. They are a PITA.

 

[hoshang]

All new columns should bear on a beam. No special detail is required, just starter dowels from beam into column.

But you proposed these W3 & W4 walls:

Walls W1, W3 and W4 may be adequate for North-South wind, but W2 is too far South to resist East-West wind. I have indicated two rigid frames, RF1 and RF2 which may be used for E-W wind, but rigid frame deflections are not the same as shear wall deflections, so there may be a torsion issue on the building as a whole unless you can add a rigid element in the wall parallel to Main Street. At the moment, that wall seems to be all windows.

Where the beams would be on gridline D & E?

If we can do this, it would help a lot, both architecturally and structurally.

can't be moved, it's a requirement.

 

[rb1957]

I don't build concrete things, so you can say I don't know what I'm talking about, but ...

1) the "2nd floor framing plan" above doesn't show the light boxes (in the middle of the floor) which would seem to mess considerably the E-W beam (on line 2) ?
Can the light box on line B be moved northwards, and so give a clear run for the beam (on line 2) ?

2) is the south wall solid ? so the structure along the south wall is a light box ? why not have windows in the south wall (and do away with the light box) ?

3) we've stopped talking about the parking ?



"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[BAretired]

Quote (BAretired)
All new columns should bear on a beam. No special detail is required, just starter dowels from beam into column.
But you proposed these W3 & W4 walls:

What is your point? On Grids D and E, the walls are the beams, one story deep; and there are no columns.

Where the beams would be on gridline D & E?

There are no beams on gridlines D and E other than walls, acting as deep beams and shear walls combined.

can't be moved, it's a requirement.

What's a requirement?...that the wall can't be moved, or the "20% open area" nonsense? Your laconic responses are not helpful.

 

[BAretired]

and BA[/color]]I don't build concrete things, so you can say I don't know what I'm talking about, but ... I would never say such a thing, rb1957.

1) the "2nd floor framing plan" above doesn't show the light boxes (in the middle of the floor) Iwhich would seem to mess considerably the E-W beam (on line 2) ?
Can the light box on line B be moved northwards, and so give a clear run for the beam (on line 2) ? I don't know. That is Architectural, but perhaps the beam can be moved.

2) is the south wall solid ? so the structure along the south wall is a light box ? why not have windows in the south wall (and do away with the light box) ? The south wall is built to property line, so windows would not do us much good if the southern neighbor builds a multi-story building to the property line. I thought we might get away with it if we could move the south wall to the north, but hosang says we can't. I'm not sure whether the 20% open requirement applies to all buildings in Iraq, or just those built up to property line. And so far, hosang has not deigned to tell us.

3) we've stopped talking about the parking ? For now, but we could resume if the project ever gets moving, a prospect which looks less likely as time moves on.

 

[hoshang]

What is your point? On Grids D and E, the walls are the beams, one story deep; and there are no columns.

There are no beams on gridlines D and E other than walls, acting as deep beams and shear walls combined.

My consideration is how the red area (a 2.85m cantilever slab area) supported since the framing columns are set back this amount (2.85m) in the 2 basement & first floors.

On gridlines A through C the cantilever slab can be supported by beams on columns extending from back to front (south) of the property line.
But here, on gridlines D & E we (I & you) proposed RC walls extending from gridline 1 through 3 (on gridline D) and from gridline 1 through 2 (on gridline E). These walls can't be extended to front (sooth) property line. So how the red area would be supported?

What's a requirement?...that the wall can't be moved, or the "20% open area" nonsense? Your laconic responses are not helpful.

the "20% open area"

 

[jayrod12]

Hoshang, I'm sorry if this is going to come across harshly, but BA has been giving you plenty of guidance, so much that any competent structural designer could run with the recommendations and figure it out. It doesn't seem like you have the structural design skills to be doing a project like this if you keep asking very basic questions about how to support the cantilever. BA has told you multiple times how he would tackle this, and to be honest he's been extremely clear. I believe the rest of us are in agreement with him how we would do it. I'd suggest going back through this ridiculously long thread and really review his sketches and guidance. If you can't figure it out after going back through everything, then you really shouldn't be trying to design this building.

You still have never actually told us why the 20% open area is a requirement. It doesn't make sense to many of us, and when we ask for clarification you just repeat yourself "20% open requirement". Why is that a requirement? What part of the code that you are designing around indicates that's a requirement? It seems extremely against most of our design codes to have just open air access between parking level and habital space above. It would honestly be the first time I've ever seen it.

 

[hoshang]

jayrod12,
seems you didn't follow the thread.
If you followed the thread, point out where I can find the answer to my 'basic questions' in my post on 5 Apr 24 07:54? Or if you can as a 'competent structural designer' provide a response for this post, please do.

 

[jayrod12]

All of your answers are in BA's posts above. Including how to support the cantilever. He has told you multiple times how to do it. If you can't find it in his information, again you shouldn't be doing this level of work.

Your responses are making us, or at least me, question whether anyone should be helping you given the clear lack of understanding of structural design you have.

I'll go back to just lurking in astonishment at how long this thread has become without you understanding any of it. Good luck.

 

[BAretired]

jayrod12,

seems you didn't follow the thread.
If you followed the thread, point out where I can find the answer to my 'basic questions' in my post on 5 Apr 24 07:54? Or if you can as a 'competent structural designer' provide a response for this post, please do.

I think that jayrod followed the thread quite well. The way I would do it is shown below. But you are the Structural Engineer of Record, hoshang, not me, so if you prefer another solution, go for it.

 

[hoshang]

Hi BAretired,
I appreciate your help and patience. I indicated my worry in blue text:

Am I right to worry about this? If so, can the green wall be supposed as a backspan for your 'Suspended from cantilever' area?

 

[brTCP]

Good answers here already. I would like to add that perhaps you could use a tool like the one described in the video below to help you with this issue:

https://www.youtube.com/watch?app=desktop&v=3kl4LHjAKio

 

[BAretired]

The black "suspended" piece is not a beam, but it looks like a beam in cross section and may be monolithic with the slab. It can be doweled into the wall to the left, but it is not relying on that for support. The black object is hanging from the cantilevered wall above, which means that forms must be kept in place until the wall above cures.

 

[hoshang]

The black object is hanging from the cantilevered wall above, which means that forms must be kept in place until the wall above cures.

But this corresponds to my post on 22 Mar 24 12:51. Isn't it?

Maybe one of the thoughts would be (RC wall) hangers from floors above.

And you replied (on 22 Mar 24 18:15) as:

I see no need for any hangers from floors above.

 

[BAretired]

Yes, you are correct. My error. At the time, I was not thinking about the First Floor but the Typical Floor.

 

[hoshang]

Hi BAretired,
your help is highly appreciated.
If other concerns faced me (regarding building configuration) with this structure, can I ask it here in this thread? Or shall I create another thread?

 

[BAretired]

I believe it might be best to create a new thread. This one is just getting too long.

EDIT: I looked at some other threads which had over 300 posts, one over 500, so perhaps it could grow a bit before starting anew.