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Design of ribbed slab

 
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dipeshtanuja
SEFI Member
SEFI Member


Joined: 26 Jan 2003
Posts: 4

PostPosted: Thu Nov 23, 2006 6:14 am    Post subject: Design of ribbed slab Reply with quote

 
Hi friends,

is anybody can help me for?

1. design steps for one-way and two-way ribbed slab, nature and behavior of ribbed slab?

2. How long we can design R.C.C Beam means max. span if grade of materials and depth of beam is not restricted?

Thanks

Dipesh

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akjhacpwd
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Joined: 26 Jan 2003
Posts: 147

PostPosted: Fri Nov 24, 2006 7:27 am    Post subject: Design of ribbed slab Reply with quote

Dear Dipesh

Ribbed slabs are not different from ordinary slabs in behaviour. For a two way ribbed slab if the clear spacing between ribs does not exceed 12 times the thickness of the topping ( which will be 80 - 100 mm) , the slab can be designed as any normal slab by IS code coefficients or any other accepted mehod. The same applies to one way ribbed slab also.

If the spacing is more , analyze it as a grid. You will get solved examples in the text books like that by Prof Dayaratnam etc.

If you are not able to solve , give another mail . I will send a worked out example.

Best wishes

AKJHA
Director , Disaster Mitigation Centre
CPWD Training Institute, Ghaziabad

dipeshtanuja[AT]red... wrote:

Hi friends,

is anybody can help me for?

1. design steps for one-way and two-way ribbed slab, nature and behavior of ribbed slab?

2. How long we can design R.C.C Beam means max. span if grade of materials and depth of beam is not restricted?

Thanks

Dipesh

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civil
SEFI Regulars
SEFI Regulars


Joined: 26 Jan 2003
Posts: 25

PostPosted: Fri Nov 24, 2006 8:27 am    Post subject: Design of ribbed slab Reply with quote

Dear Sir,

It will be helpful if you send one worked out example.

Regards,

Sachin Kulkarni
Garware Polyester Ltd.

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mandarsdandekar at yah...
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PostPosted: Sat Nov 25, 2006 4:58 pm    Post subject: Design of ribbed slab Reply with quote

Dear Dipesh,
This regarding the Maximum Span of RCC beam, There are Clause in IS456-2000 which specifies the Slenderness Limit of Beam. It says
A beam is usually a vertical load-carrying member. However, for long span the beam may bend laterally. To ensure the lateral stability of beam, the criteria’s are
1. For simply Supp. or Continuous  Beam, Clear dist. Betwn lateral restraints shd not exceed 60b or 250b2/d, whichever is less where d is eff. Depth.
2. For Canti. Clear Dist frm free end of beam to the lateral restraint shall not exceed 25b or 100b2/d, whichever is less.

Regards
Mandar S. Dandekar

civil[AT]gar... wrote:  Dear Sir,

It will be helpful if you send one worked out example.

Regards,

Sachin Kulkarni
Garware Polyester Ltd.

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lalrajesh
SEFI Member
SEFI Member


Joined: 26 Jan 2003
Posts: 4

PostPosted: Mon Nov 27, 2006 4:59 am    Post subject: Design of ribbed slab Reply with quote

Sir,

Thanks for the guidance on ribbed slab. But what about the grid beam
reinforcements. What moment has to be considered for deciding the
reinforcement in the ribs. If the span is large, isn,t it true that a grid
of main and secondary grid beam is to be analysed with secondary beams
resting ( Moments released)on the main beams. Please send a worked out
example.  Sir, I have been reading your replies in the SEFI. I m very
impressed with the solutions given by you which satisfies both the theory
and practice.

Regards
Rajesh lal
-----Original Message-----
Message From  akjhacpwd[AT]yah... [mailto:akjhacpwd[AT]yah...]
Sent: Friday, November 24, 2006 12:58 PM
To: lalrajesh[AT]dat...
Subject: Design of ribbed slab

Dear Dipesh

Ribbed slabs are not different from ordinary slabs in behaviour. For a two
way ribbed slab if the clear spacing between ribs does not exceed 12 times
the thickness of the topping ( which will be 80 - 100 mm) , the slab can be
designed as any normal slab by IS code coefficients or any other accepted
mehod. The same applies to one way ribbed slab also.

If the spacing is more , analyze it as a grid. You will get solved
examples in the text books like that by Prof Dayaratnam etc.

If you are not able to solve , give another mail . I will send a worked
out example.

Best wishes

AKJHA
Director , Disaster Mitigation Centre
CPWD Training Institute, Ghaziabad

dipeshtanuja[AT]red... wrote:

Hi friends,

is anybody can help me for?

1. design steps for one-way and two-way ribbed slab, nature and behavior of
ribbed slab?

2. How long we can design R.C.C Beam means max. span if grade of materials
and depth of beam is not restricted?

Thanks

Dipesh

Find out what India is talking about on  - Yahoo! Answers India
Send FREE SMS to your friend's mobile from Yahoo! Messenger Version 8. Get
it NOW

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sdec
SEFI Regulars
SEFI Regulars


Joined: 26 Jan 2003
Posts: 26

PostPosted: Mon Nov 27, 2006 5:53 am    Post subject: Design of ribbed slab Reply with quote

Dear Rajesh
Please ensure that your reinforcement detailing conforms to your
analysis.........it is v important. If your secondary beam has a release at
the junction with the main beam, then your top steel of the secondary beam
should not be bent into the main beam....in fact we shd not give full Ld to
this r/f .Otherwise it will not be a released end practically
If you are good at Staad modelling, this ribbed slab can be modelled as a
floor with all the main beams and all the secondary beams as well along with
your normal 3-D model with the releases at appropriate locations. The
results can be cross checked by you with a manual calculation as well.In
case the spans are large, pl look at the minimum size criteria for the beams
vis a vis the clause of IS 456 which says the span can be 60 x b or 250 x
bxb/d, whichever is lesser.It is always better to have main beams and
columns as a little generously sized......
Regards
Sangeeta wij

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akjhacpwd
Silver Sponsor
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Joined: 26 Jan 2003
Posts: 147

PostPosted: Fri Dec 08, 2006 2:01 pm    Post subject: Design of ribbed slab Reply with quote

Dear friends
Shortly i will post an attachment clarifying these doubts. If permittedc by NICEE , i will post that to its site. But bear with me for some time due to other pressing jobs of administration, teaching in the class and attending to colleague's problems.

AKJHA

lalrajesh[AT]dat... wrote:
Sir,

Thanks for the guidance on ribbed slab. But what about the grid beam
reinforcements. What moment has to be considered for deciding the
reinforcement in the ribs. If the span is large, isn,t it true that a grid
of main and secondary grid beam is to be analysed with secondary beams
resting ( Moments released)on the main beams. Please send a worked out
example. Sir, I have been reading your replies in the SEFI. I m very
impressed with the solutions given by you which satisfies both the theory
and practice.

Regards
Rajesh lal
-----Original Message-----
Message From  akjhacpwd[AT]yah... [mailto:akjhacpwd[AT]yah...]
Sent: Friday, November 24, 2006 12:58 PM
To: lalrajesh[AT]dat...
Subject: Design of ribbed slab

Dear Dipesh

Ribbed slabs are not different from ordinary slabs in behaviour. For a two
way ribbed slab if the clear spacing between ribs does not exceed 12 times
the thickness of the topping ( which will be 80 - 100 mm) , the slab can be
designed as any normal slab by IS code coefficients or any other accepted
mehod. The same applies to one way ribbed slab also.

If the spacing is more , analyze it as a grid. You will get solved
examples in the text books like that by Prof Dayaratnam etc.

If you are not able to solve , give another mail . I will send a worked
out example.

Best wishes

AKJHA
Director , Disaster Mitigation Centre
CPWD Training Institute, Ghaziabad

dipeshtanuja[AT]red... wrote:

Hi friends,

is anybody can help me for?

1. design steps for one-way and two-way ribbed slab, nature and behavior of
ribbed slab?

2. How long we can design R.C.C Beam means max. span if grade of materials
and depth of beam is not restricted?

Thanks

Dipesh

Find out what India is talking about on - Yahoo! Answers India
Send FREE SMS to your friend's mobile from Yahoo! Messenger Version 8. Get
it NOW

Find out what India is talking about on  - Yahoo! Answers India
Send FREE SMS to your friend's mobile from Yahoo! Messenger Version 8. Get it NOW

Posted via Email
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