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Flat slab under wall loading
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ykalamkar
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Joined: 26 Jan 2003
Posts: 108
Location: Nagpur

PostPosted: Mon Jan 05, 2009 11:59 am    Post subject: Flat slab under wall loading Reply with quote

Yes madam,  
I am talking about brick wall partitions as in say shopping mall with flat slab, there are 9” thk brick wall near passages. Is it necessary to apply line load or calculate moment as per reynolds handbook? Or we can increase the equivalent wall load?
Dear Dr.Subramanian sir,
When there is 24 m length of wall total equivalent wall load is 24*12/64 = 4.5 kN/m2.  
Regards
Yogesh  
From: sdec.in [mailto:forum@sefindia.org]
Sent: Monday, January 05, 2009 3:46 PM
To: econf@sefindia.org
Subject: [ECONF] Re: Flat slab under wall loading



But as I understand from his mail, Mr Kalamkar is discussing walls which are other than light partitions; in our country walls are still either 9" or 4 and a half " brick work(or block work) which translates into substantial line loads and need to be carefully handled in flat slabs( in case of beam-slab structures, for example, we do not allow any 9" brick walls on slabs and provide suitable beams underneath them).

Regards
Sangeeta Wij
Quote:
----- Original Message -----
From: Ramachandran. K.S (forum@sefindia.org (forum@sefindia.org))
To: econf@sefindia.org (econf@sefindia.org) (econf@sefindia.org (econf@sefindia.org))
Sent: 05 January, 2009 2:32 PM
Subject: [ECONF] Re: Flat slab under wall loading


Dear Dr.Subramanian & Mr.Yogesh Kalmkar,

This is covered in Clause 3.1.2 with the heading "Load due to light partitions" in IS:875 part-2.

Regards,
K.S.Ramachandran
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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: Mon Jan 05, 2009 3:52 pm    Post subject: Flat slab under wall loading Reply with quote

Dear Mr.Kalamkar,

Yes. My friend Mr. Varyani has made a valid point. I failed to notice the high wall height of 4m. Moreover I thought it was a linear wall but from your reply I understand that 24m wall is in 8 m sq. flat slab, probably enclosing a room. As Mr. Varyani and Ms.  Sangeeta Wij have rightly pointed out, thick walls have to be supported on beams, otherwise may lead to cracking. Moreover studies have not been conducted (to my knowledge) on flat slabs for the influence of such walls.

Late Prof. P. Purushothaman, in his classical book RC Structural Members-Behaviour, Analysis and Design(TMH,1984) has given some guideline and an example for considering Point and line loads on slabs based on yield line theory(see page 608-613 of the book).

You may also like to see some specialist literature on the subject. Please go through the book Park, R., and Gamble, W.L. Reinforced Concrete Slabs, 2nd Edition, Wiley, 1999, 736pp (see Section 3.5 & 7.5). You may also like to refer some Bridge books, as concentrated loads are encountered more in bridge slabs.

I take this opportunity to add a few line about Slabs. Slab design is taken lightly by many engineers, as it is often done using the coefficients given in IS 456. But Prof. P.P. has devoted 261 pages for slabs(about 38% of his book). Slabs often are forgiving as far as strength is concerned but when they are not designed and detailed properly will result in several serviceabilty problems, like cracking, deflection, and vibration. I have seen several large spans vibrating, if you just jump on them or when a wheel burrow is run over them.

Best wishes
NS

Dr.N.Subramanian,Ph.D.,F.ASCE, M.ACI,

Consulting Structural Engineer
Maryland, USA

See my books at: www.multi-science.co.uk/subramanian-book.htm
www.oup.co.in/search_detail.php?id=144559





--- On Mon, 1/5/09, uhvaryani <forum@sefindia.org> wrote:
Quote:
From: uhvaryani <forum@sefindia.org>
Subject: [SEFI] Re: Flat slab under wall loading
To: general@sefindia.org
Date: Monday, January 5, 2009, 1:04 PM

dear mr.kalamkar,
major brick walls should be made to rest on beams.brick partition walls resting directly
on slab are likely to get cracked due to variable deflection of slab panels.4.0 to 5.0m
high patition walls,mentioned in some dispatches are quite unusual in common buildings.
storey heights in buildings are of the order of 3.0 to 3.5m.
with regards,
uhvaryani
     



     



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Dr. N. Subramanian
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PostPosted: Tue Jan 06, 2009 6:16 pm    Post subject: Re: Flat slab under wall loading Reply with quote

Dear Mr. Yogesh,

Since  not much is known about the behaviour of flat slabs under such loads(The studies mentioned by me are made on ordinary slabs), you may do the following:

1. Apply a line load where the wall is coming and analyse the slab(you may also apply the equivalent UDL and get the results, just for compariso and checking).
2. Add additional rods at the top and bottom of the slab, where the wall is resting, for a width of 230+ d on either side, and provide nominal shear reinforcement. This will prevent the cracking of slab.

But I feel that in such cases(where heavy walls are resting on slab), flat plates will not be economical, as you are unnecessarily increasing the depth of slab throughout!

Best wishes
Subramanian
ykalamkar wrote:
Yes madam,  
I am talking about brick wall partitions as in say shopping mall with flat slab, there are 9 thk brick wall near passages. Is it necessary to apply line load or calculate moment as per reynolds handbook? Or we can increase the equivalent wall load?
Dear Dr.Subramanian sir,
When there is 24 m length of wall total equivalent wall load is 24*12/64 = 4.5 kN/m2.  
Regards
Yogesh  
From: sdec.in [mailto:forum@sefindia.org]
Sent: Monday, January 05, 2009 3:46 PM
To: econf@sefindia.org
Subject: [ECONF] Re: Flat slab under wall loading



But as I understand from his mail, Mr Kalamkar is discussing walls which are other than light partitions; in our country walls are still either 9" or 4 and a half " brick work(or block work) which translates into substantial line loads and need to be carefully handled in flat slabs( in case of beam-slab structures, for example, we do not allow any 9" brick walls on slabs and provide suitable beams underneath them).

Regards
Sangeeta Wij
Quote:
----- Original Message -----
From: Ramachandran. K.S (forum@sefindia.org (forum@sefindia.org))
To: econf@sefindia.org (econf@sefindia.org) (econf@sefindia.org (econf@sefindia.org))
Sent: 05 January, 2009 2:32 PM
Subject: [ECONF] Re: Flat slab under wall loading


Dear Dr.Subramanian & Mr.Yogesh Kalmkar,

This is covered in Clause 3.1.2 with the heading "Load due to light partitions" in IS:875 part-2.

Regards,
K.S.Ramachandran
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ibarua
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PostPosted: Thu Jan 08, 2009 4:35 am    Post subject: Flat slab under wall loading Reply with quote

9th Jan 2009

It's imperative to calculate the actual moments coming from such strip loads. I had to write a program when confronted with the problem when designing deck slabs of bridges under wheel loads, as well as strip loads of walls on building slabs. The program is based on the expression for the deflection of a plate under a concentrated load (Timoshenko & Kreiger - 'Theory of Plates & Shells')in the form of a rectangle. The program is for a plate simply supported at the edges. I would use it in a flat slab -- the error would be on the side of safety, as flat slab are not exactly simply supported at the edges. Curves designed by A. Pigeaud (1923) could also be used, but these are approximations.

Indrajit Barua.

On Mon, 05 Jan 2009 ykalamkar wrote :
Quote:
Yes madam,  
I am talking about brick wall partitions as in say
shopping mall with flat slab, there are 9 thk brick
wall near passages. Is it necessary to apply line load
or calculate moment as per reynolds handbook? Or we can
increase the equivalent wall load?
Dear Dr.Subramanian sir,
When there is 24 m length of wall total equivalent wall
load is 24*12/64 = 4.5 kN/m2.  
Regards
Yogesh  
From: sdec.in [mailto:forum@sefindia.org]
Sent: Monday, January 05, 2009 3:46 PM
To: econf@sefindia.org
Subject: [ECONF] Re: Flat slab under wall loading



But as I understand from his mail, Mr Kalamkar is
discussing walls which are other than light partitions;
in our country walls are still either 9" or 4 and a
half " brick work(or block work) which translates into
substantial line loads and need to be carefully handled
in flat slabs( in case of beam-slab structures, for
example, we do not allow any 9" brick walls on slabs
and provide suitable beams underneath them).

Regards
Sangeeta Wij

Quote:
----- Original Message -----
From: Ramachandran. K.S (forum@sefindia.org
(forum@sefindia.org))
Quote:
To: econf@sefindia.org (econf@sefindia.org)
(econf@sefindia.org (econf@sefindia.org))
Quote:
Sent: 05 January, 2009 2:32 PM
Subject: [ECONF] Re: Flat slab under wall loading


Dear Dr.Subramanian & Mr.Yogesh Kalmkar,

This is covered in Clause 3.1.2 with the heading
"Load due to light partitions" in IS:875 part-2.
Quote:

Regards,
K.S.Ramachandran
--auto removed--  








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thirumalaichettiar
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PostPosted: Wed Jan 14, 2009 2:02 pm    Post subject: Re: Flat slab under wall loading Reply with quote

[quote="sdec.in"]But as I understand from his mail, Mr Kalamkar is discussing walls which are other than light partitions; in our country walls are still either 9" or 4 and a half " brick work(or block work) which translates into substantial line loads and need to be carefully handled in flat slabs( in case of beam-slab structures, for example, we do not allow any 9" brick walls on slabs and provide suitable beams underneath them).

Regards
Sangeeta Wij
Quote:
----- Original Message -----
From: Ramachandran. K.S (forum@sefindia.org)
To: econf@sefindia.org (econf@sefindia.org)
Sent: 05 January, 2009 2:32 PM
Subject: [ECONF] Re: Flat slab under wall loading


Dear Dr.Subramanian & Mr.Yogesh Kalmkar,

This is covered in Clause 3.1.2 with the heading "Load due to light partitions" in IS:875 part-2.

Regards,
K.S.Ramachandran
--auto removed--

Posted via Email

First of all let me clarify that the below quote is not for Flat slab/Flat plate over which 9" wall rest. This is for the normal slab supported over masonry/RCC beams.

I agree with Madam Sangetha Viji regarding the 9" wall over slab which require many times a beam under the slab. Well  many clients as well as Architects provide a Hall in GF/FF of size 20'x16' or so and over the hall a room will be proposed for other fuctions . In that case the clients does not want beam under the slab in Hall of GF / FF and also as per Vasthu single beam is not a good omen as per Vasthu consultant. So under the above circumstances what is the solution?

I faced the above in many residential building designs.

I always go for a beam but under many special circumstances I refer either the Reinforced Concrete Designers's HB by REynold table 4 wherein the equivalent load/sq.m can be arrived and added to the other DL+LL to arrive at the BM.
Or I refer the table given in Mini Technical HB -1996 by Tamilnadu PWD in which an interesting and valuable guidance has given for arriving at the BM due to partitions even not at the center of span. The table is based on M-Pigeaud's theory.The table gives -factors to be mutiplied with the wall load/sq.m of the area of slab which is a wise solution. With this idea the load will be dispersed over a good effective area and the reinforcement is arrived at.
I could not attach the table(TPWD) in excel form but I will send through Gereal forum which can be downloaded.
I suggest the SEFI to add in the web site so that anybody interested can download and use and send their comments.
I invite comments and any other solutions against my design technic.

_________________
T.Rangarajan,B.E,M.Sc(Struc.Engg),FIE,CE,MACI.Consulting Structural engineer,
Coimbatore,
Download My Tips : http://www.sefindia.org/rangarajan
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