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dipeshtanuja SEFI Member
Joined: 26 Jan 2003 Posts: 4
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Posted: Thu Nov 23, 2006 6:14 am Post subject: Design of ribbed slab |
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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 Silver Sponsor
Joined: 26 Jan 2003 Posts: 147
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Posted: Fri Nov 24, 2006 7:27 am Post subject: Design of ribbed slab |
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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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civil SEFI Regulars
Joined: 26 Jan 2003 Posts: 25
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Posted: Fri Nov 24, 2006 8:27 am Post subject: Design of ribbed slab |
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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... Guest
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Posted: Sat Nov 25, 2006 4:58 pm Post subject: Design of ribbed slab |
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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
Joined: 26 Jan 2003 Posts: 4
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Posted: Mon Nov 27, 2006 4:59 am Post subject: Design of ribbed slab |
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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
Joined: 26 Jan 2003 Posts: 26
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Posted: Mon Nov 27, 2006 5:53 am Post subject: Design of ribbed slab |
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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
Joined: 26 Jan 2003 Posts: 147
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Posted: Fri Dec 08, 2006 2:01 pm Post subject: Design of ribbed slab |
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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
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