Structural challenges 1

[Refaatfaraj]

Hi all

I have some a challenges to select the suitable structural system for administration building with large spans.
Could someone help me to suggest a suitable structural system since we have in the ground floor a hall room (12 m width variable , about 25 m length variable)( please , take a look to the attached captures) and its RC slab extended from all hall sides ( about 2m each side and one side about 4 m) while as in the first and second floor there is also hall (16 m width , 20m length also variable) which means the external column of the first and the second floor are supported on the cantilever of ground floor slab .
Knowing that the architect doesn’t want any internal columns inside the halls. it means that the span length of ground floor slab will be (12m short direction with the cantilever extension from both sides which are supported the column of upper floors .

My first attempt is to use RC frames (beams & columns) in ground floor then the external columns of upper floors will be supported on the cantilever beams of ground floor.


Which one do you think the best chose or do you have any other suggestions?

Knowing that the prestressed system is undesirable in this project. Only RC Structural systems.

Any advice or hint will be highly appreciated.

Best Regards

Refaat

 

[BAretired]

You have shown only partial floor plans. How can you expect anyone to come up with a framing system based on incomplete information?

Why only RC structural systems? Maybe some story deep structural steel trusses would make sense.

BA

 

[Refaatfaraj]

Hi @BAretired


Thank you for your response.

Those pictures were attached to my first post only showing up that part of building needs to find special structural solution since have large spans only in this zone of building.

However, the plans Auto cad file is attached here. Knowing that the height of ground story is (5m – clear height) while as the first and second stories height is (4m – clear height).

I think the steel truss system will be not a suitable with this irregular building geometry and limited story height. Because I expect the truss height will be more than 1.2m for spans about (17 m) which will deeply effect in the story height. Also, we have to consider the privacy of the building as an administrative building.

Actually , I was thinking to use steel frames as framing system to support the RC slabs But unfortunately the owner consultant insist on using only RC structural system in this project .


Therefore, after a deep thought has reached to treat with each story separately. On other hand change some of brick walls to RC walls based on the architectural conception for each story to support flat slabs. I know that this system will lead to vertical irregularity which is should be considered when the structure exposed to seismic loads. IMHO that the most important point here to try keeping both (the story gravity center & the geometry center) to closed.

I look forward to hear from you about this proposal or have another better suggestion.

Thank you in advance

Refaat

 

[dik]

You can make 'floor' blocks of the different levels and superimpose them to see where there are common points where you can put supports. A lot of your long span areas can be broken down into shorter span. This is less expensive and structurally more stiff.

More interesting, I don't know how your stairwells work There appear to be two located within the floor area, but, if used for fire exiting they should be located near exterior walls, else, you likely have problems with providing a fire rated corridor to the outside. Don't know what your code requires.

Dik

 

[Refaatfaraj]

Hi @ Dick

I really appreciated your response.

(You can make 'floor' blocks of the different levels and superimpose them to see where there are common points where you can put supports. )

Please, Could you give me more explanations to clarify your idea? If attached with some an example will be better.

Thank you

Refaat

 

[dik]

See attached zip file... has all floors loaded as different drawings.

Use the lowest floor plan and open it in CAD. Then treat the other dwg files as blocks and you can place the one layer over the lowest floor plan and see where common points of support are... do that for all floors. Error in uploading file...

Dik

 

[dik]

Another try...

 

[dik]

and another...

 

[dik]

and yet another...

 

[Refaatfaraj]

Hi @ Dick

Thank you so much .

I am really sorry because there was misunderstanding. I get your point . Actually this is what I am usually doing . But the challenges of this project the vertical elements cant be fit with the architecture design since there is irregularity in internal brick walls distributions and many of external walls are glass walls . Therefore I am thinking to change these walls to Concrete walls to support the slab floor . in this case each floor have own concrete wall distribution . on anther hand I will treat with each floor slab as ( Raft slab ) .

I hope the structural proposal of this project is clear to you .

Please , Could I hear your opinion about my structural system proposal ?

Thanks in advance

Refaat

 

[BAretired]

I can't read any of the DWG files. My version of Autocad is pretty old (2006) and apparently doesn't function with my current operating system (Windows 10). I seldom have occasion to use it, so have not bothered to upgrade.

BA

 

[Refaatfaraj]

Hi @BAretired

Thank you for your interest .

Here you are .

Attached file has been saved on CAD 2000

Best Regards

Refaat

 

[Refaatfaraj]

Hello all

For better understanding the architecture project idea . Some shots have attached on this post

Thanks in advance.

Refaat

 

[Refaatfaraj]

Hello all

Also, one capture from my structural model in (Autodesk ROBOT Structural Analysis Professional 2018)

is attached here to clarify my proposal

Best Regards
Refaat

 

[dik]

Nice building and very complex... you need some walls/beams to support the long cantilevers on the right had side. Good luck. Is the exiting OK?

Dik

 

[Refaatfaraj]

Hello Dik


I just build up my structural model in ROBOT based on my idea . I need maybe two days to complete it . Then I will run the model and find out the analysis results. I wrote this thread to see if my structural proposal is the best choice or there is another structural proposal for this building .

Thank you

Refaat

 

[dik]

You have all sorts of possible internal locations for support. Minimising the spans can be a cost saving measure.

Dik

 

[Refaatfaraj]

Hi @Dick

Exactly , this is what I am trying to do .

Refaat