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Tall buildings with ALL RCC WALLS
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Dr. N. Subramanian
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Joined: 21 Feb 2008
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Location: Gaithersburg, MD, U.S.A.

PostPosted: Wed Nov 28, 2012 4:43 am    Post subject: Re: Tall buildings with ALL RCC WALLS Reply with quote

Dear Er Kapil and Er Biju,

Are you talking about Tunnel form system? I am not sure whether it has been adopted in tall buildings. Anyway the behaviour of such system under lateral loads may be found at:
http://nsmp.wr.usgs.gov/ekalkan/PDFs/A47_Yuksel_Kalkan.pdf

Best wishes,
NS
biju wrote:
Dear Mr. KapilDingare,

There are many tall buildings coming up with this framing system ( All walls in RCC )now a days. The advantage is that there will not be any projections inside the rooms, Architect/end users are happy.
Speed  of construction increases rapidly, will have better finishes, better member joints, increase in the usable carpet area, much stiffer structure to resist wind effects, and abundance of shear walls in both directions to resist seismic forces etc...

The disadvantage is that no future modifications or breaking of walls, partly or fully is possible.  Also need of skilled labors, good quality control,proper design and detailing, and no more changes once the construction has started.

The cost of construction does not increase much, and found that in some cases, there is actually a reduction in the overall cost.

regards,

Biju.




<if>1)     <endif>Tall R.C.C. building with all walls (internal aswell as external) as R.C.C. structural walls,in which type all walls columns,beams are casted together(like in aluminum formwork like in Mihan or similar)
<if>2)     <endif>Tall R.C.C. framed buildings with walls as partitionwalls and non structural members in which frames are made first and  non structural partitions later.

<o> </o>
With respect to following points
1) What type of loads R.C.C. walls wouldcarry?
2) Would bending in beams in both the casessame or different ?
3) Would columns carry same axial force andmoments in both the cases?
4) Would these walls act as shear walls?What would be their role with respect to lateral loads?
5) If these walls are discontinued at stiltfloor what precautions are taken to offset such high stiffness discontinuity?
6) In analyzing such frames with structuralwalls how these walls are modeled?
<o> </o>
                                  Thank you ,verymuch.
<o> </o>
<o> </o>
                                                                                                         KapilDingare
[/quote]
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kapildingare
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Joined: 15 May 2009
Posts: 103

PostPosted: Wed Nov 28, 2012 5:44 am    Post subject: Reply with quote

Resp Dr Subramanian,

               Thank you for your reply,I dont know about tunnel form ,you have mentioned,but I am talking about construction practices now a days common for buildings of 25 stories (residential and or commercial  )with plate area around anything 1000 smt..

                               In this type of construction after stilt floor slab formwork for all walls (internal as well as external for full plate area) is erected with top slab in one or max two go and concreted together with mostly aluminium formwork (aluform,mihan or like) for a floor and then it is repeated for no. of floors.With this type one get frame as well as walls constructed together and that too all in RCC structural elements.

Regarding this type of construction I would like your and other experts opinion with following points.


1) What type of loads R.C.C. walls would carry?
2) Would bending in beams in both the cases same or different ?
3) Would columns carry same axial force and moments in both the cases?
4) Would these walls act as shear walls? What would be their role with respect to lateral loads?
5) If these walls are discontinued at stilt floor what precautions are taken to offset such high stiffness discontinuity?
6) In analyzing such frames with structural walls how these walls are modeled.


   Thank you ,



                                                                  Kapil Dingare
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Dr. N. Subramanian
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Joined: 21 Feb 2008
Posts: 5282
Location: Gaithersburg, MD, U.S.A.

PostPosted: Wed Nov 28, 2012 6:00 am    Post subject: Reply with quote

Dear Er Kapil,
Please read the paper in the link provided. I think what you have mentioned and I what I say are  the same!
1) What type of loads R.C.C. walls would carry?
All this will act as load bearing wall and at the same time as shear walls.

2) Would bending in beams in both the cases same or different ?
Are there beams? If there are secondary beams they will act as in regular  buildings.

3) Would columns carry same axial force and moments in both the cases?
I do not think there will be columns. If there are a few columns, they will be designed as gravity load columns, as their stiffness will be comparatively less than walls.

4) Would these walls act as shear walls? What would be their role with respect to lateral loads?
Yes. Exactly like shear walls. Do you know that there are steel walls also, called steel plate shear walls. see: http://www.modernsteel.com/uploads/issues/april_2005/30740_selie.pdf
Recently  steel plate shear walls has been adopted for a 75 storey building in China:
http://www.ctbuh.org/LinkClick.aspx?fileticket=oGDpSIrMUqI%3D&tabid=2566&language=en-US
5) If these walls are discontinued at stilt floor what precautions are taken to offset such high stiffness discontinuity?
It will be highly dangerous to discontinue them at stilt level.

6) In analyzing such frames with structural walls how these walls are modeled.

They may be modeled as plate elements or shell elements.

Best wishes,
NS
kapildingare wrote:
Resp Dr Subramanian,

               Thank you for your reply,I dont know about tunnel form ,you have mentioned,but I am talking about construction practices now a days common for buildings of 25 stories (residential and or commercial  )with plate area around anything 1000 smt..

                               In this type of construction after stilt floor slab formwork for all walls (internal as well as external for full plate area) is erected with top slab in one or max two go and concreted together with mostly aluminium formwork (aluform,mihan or like) for a floor and then it is repeated for no. of floors.With this type one get frame as well as walls constructed together and that too all in RCC structural elements.

Regarding this type of construction I would like your and other experts opinion with following points.


1) What type of loads R.C.C. walls would carry?
2) Would bending in beams in both the cases same or different ?
3) Would columns carry same axial force and moments in both the cases?
4) Would these walls act as shear walls? What would be their role with respect to lateral loads?
5) If these walls are discontinued at stilt floor what precautions are taken to offset such high stiffness discontinuity?
6) In analyzing such frames with structural walls how these walls are modeled.


   Thank you ,



                                                                  Kapil Dingare
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kapildingare
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PostPosted: Wed Nov 28, 2012 6:17 am    Post subject: Reply with quote

Resp Dr Subramanian,

  Thank you very much for your reply,

Part of your reply

         5) If these walls are discontinued at stilt floor what precautions are taken to offset such high stiffness discontinuity?
It will be highly dangerous to discontinue them at stilt level.
                             
              But in practice , in this type of construction ,such walls are always discontinued below stilt level.There are many works going on with this practice.

                    I would be very happy and thankful to you  if you would give some more information reading links regarding merits ,demerits with,

1)building frames with RCC frame with shear wall
2)building frame with RCC frame with bracing concrete and or steel
3) building frame with all walls as RCC walls with formwork like Aluform or Mihan or like

                   I would be thankful to other senior Sefians also who have actually taken part in such type of building design if they also explain the case .


        Thank you

                                                                  Kapil Dingare
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