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Flat Slab Design

 
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pkm1526
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Joined: 26 Jan 2003
Posts: 11

PostPosted: Wed Dec 20, 2006 5:19 am    Post subject: Flat Slab Design Reply with quote

Dear Sefians

I have a question related to flat slab design, request experts to kindly advise me.

1) Any special reinforcement is required in column head ( Flared porion) or only
columns main reinforcement is enough.
2) Is there any reinforcement requird in drop bottom layer, let us say we have 200 mm
thick flat slab and at drop thickness is 250 ,so the bottom steel of flat slab continue
only at 200 mm level, but what about steel at 250 mm level, here distance is refered from slab top surface.

Kindly give your suggestions or any reference which talk in detail on detailing of
flat slab

Regards

Prashant

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civil
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Joined: 26 Jan 2003
Posts: 25

PostPosted: Wed Dec 20, 2006 12:43 pm    Post subject: Flat Slab Design Reply with quote

Dear Prashant,

The enlarged portion of coloumn is called capital of the coloumn and yes it
has reinforcement in the conical shape without which there is no meaning to
the coloumn capital.
This is done do resist the punching shear caused due to small portion of
colomn on the slab (reaction).

As far as double reinforcement in the slab is concerned it is to be
calculated in the design.

Hope this solves your queries.

Regards,

Sachin Kulkarni
98500-79070.

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raju_goa
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Joined: 26 Jan 2003
Posts: 37

PostPosted: Wed Dec 20, 2006 1:58 pm    Post subject: Flat Slab Design Reply with quote

Dear Prashant,

Basically the mode of failure in a flat slab is by punching shear.The column
head [flared portion] is made so , such that it help in reducing shear
stress ie. you increase effective depth at column head  and not the entire
slab. Similar to what we do for a trapezoidal footing.However, it is not
mandatory that you have a column head for flat slabs. Flat slabs can be
designed even without column capitals provided the thickness of the slab is
sufficient to take care of the punching shear for the intended load. Flat
slab design is not a flexible system as compared to a traditional beam
column system. Regarding the steel in the drop panel you can refer Advance
RCC design by Bhavikatti[New age international Publishers] or any other
Advance RCC design books.
Hope I have clarified your doubt.

Regards,
Shekhar Panandiker

SHEKHAR PANANDIKER & ASSOCIATES
Consulting Structural Engineers
Wing A, second floor, Heeraniketan,
Margao - Goa 403601
INDIA

Tel:+91-832-2738399, 2705947
Fax:+91-832-2705947
Our new E-mail id is:  panandiker_goa[AT]dat... .
Please reply on our new E-mail id in future

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Jayant Lakhlani
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Joined: 26 Jan 2003
Posts: 191
Location: Rajkot, Gujarat, India

PostPosted: Thu Dec 21, 2006 4:41 am    Post subject: Flat Slab Design Reply with quote

Dear friends,

I suggest to extend the ongoing discussion on 'flab slab design' to performance of flat slab system during an earthquake event. In many cities, buildings with flab slab system are coming up (post tenstioned flab slab system included), wherein the structural system is apparently unadequate to resist seismic forces. (From MRF system, beams removed and flat slab introduced but no provision for shear walls)

Regards.

-Jayant Lakhlani

raju_goa[AT]san... wrote:
Dear Prashant,

Basically the mode of failure in a flat slab is by punching shear.The column
head [flared portion] is made so , such that it help in reducing shear
stress ie. you increase effective depth at column head and not the entire
slab. Similar to what we do for a trapezoidal footing.However, it is not
mandatory that you have a column head for flat slabs. Flat slabs can be
designed even without column capitals provided the thickness of the slab is
sufficient to take care of the punching shear for the intended load. Flat
slab design is not a flexible system as compared to a traditional beam
column system. Regarding the steel in the drop panel you can refer Advance
RCC design by Bhavikatti[New age international Publishers] or any other
Advance RCC design books.
Hope I have clarified your doubt.

Regards,
Shekhar Panandiker

SHEKHAR PANANDIKER & ASSOCIATES
Consulting Structural Engineers
Wing A, second floor, Heeraniketan,
Margao - Goa 403601
INDIA

Tel:+91-832-2738399, 2705947
Fax:+91-832-2705947
Our new E-mail id is: panandiker_goa[AT]dat... .
Please reply on our new E-mail id in future

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mkalgal
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Joined: 26 Jan 2003
Posts: 54

PostPosted: Thu Dec 21, 2006 8:31 am    Post subject: Flat Slab Design Reply with quote

Dear Sir,
I agree. Shear walls and/or core walls are a must. Flat slab buildings
are inferior to MRF in handling lateral loads. If shear walls and core
walls are provided, the slab will act as a diaphragm transfering the
lateral loads to them. It is also important to ensure that a load path
exists to the walls.
Regards
Kalgal

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shaik.riaz
SEFI Member
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Joined: 26 Jan 2003
Posts: 5

PostPosted: Fri Dec 22, 2006 4:08 pm    Post subject: Flat Slab Design Reply with quote

hai all,
my name riaz.there has been a lot of discussion on lat slabs guys i am
also doing a problem on a circular slab o 0.8 m and 7m dia slab placed on 8
vetertical slabs of 0.5 m thickness and 2.7 m height and 6m length rom outer
circumfernece of the circlular slab going inside placed radially at 8 radial
intervals. i have fixed the the bottom end of walls in all degrees of
freedom. i am analyzing this model of concrete subjected to thermal gradiant
of 40 degrees from bottom to top.
i have doing this problem in gt strudl analysing using finite element
method.
i am not able to interpret the results as i can't find any method to
verfiy my results.
any one who can help me
thanks in advance

On Wed Dec 20 19:28:11 2006, raju_goa[AT]san... <raju_goa[AT]san...>
wrote:
[quote]
Dear Prashant,

Basically the mode of failure in a flat slab is by punching shear.Thecolumn
head [flared portion] is made so , such that it help in reducing shear
stress ie. you increase effective depth at column head  and not the entire
slab. Similar to what we do for a trapezoidal footing.However, it is not
mandatory that you have a column head for flat slabs. Flat slabs can be
designed even without column capitals provided the thickness of the slab
is
sufficient to take care of the punching shear for the intended load. Flat
slab design is not a flexible system as compared to a traditional beam
column system. Regarding the steel in the drop panel you can refer Advance
RCC design by Bhavikatti[New age international Publishers] or any other
Advance RCC design books.
Hope I have clarified your doubt.

Regards,
Shekhar Panandiker

SHEKHAR PANANDIKER & ASSOCIATES
Consulting Structural Engineers
Wing A, second floor, Heeraniketan,
Margao - Goa 403601
INDIA

Tel:+91-832-2738399, 2705947
Fax:+91-832-2705947
Our new E-mail id is:  panandiker_goa[AT]dat... .
Please reply on our new E-mail id in future

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