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Reinforcement At Compression(Bottom side) of cantilever

 
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Aatif
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PostPosted: Thu Dec 12, 2019 11:55 am    Post subject: Reinforcement At Compression(Bottom side) of cantilever Reply with quote

Are Reinforcements (main reinforcements) even Provided on Compression Side(bottom) of Cantilever?

If Yes, In which Conditions it needs to be Provided and Why.
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es_jayakumar
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PostPosted: Sat Dec 14, 2019 3:58 pm    Post subject: Reply with quote

For a cantilever slab, main reinforcement (other than min. temperature reinforcement) need not be given at bottom, for gravity loads, since they will not considerably increase the moment capacity of the slab section. Some minimum steel, if provided in the bottom, will take care of possible stress reversals during earthquake.
If a cantilever beam is designed as a doubly reinforced one, then the (main)  compression reinforcement will be provided in the bottom.

E S Jayakumar
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Aatif
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PostPosted: Mon Dec 16, 2019 10:12 am    Post subject: Reply with quote

es_jayakumar wrote:
For a cantilever slab, main reinforcement (other than min. temperature reinforcement) need not be given at bottom, for gravity loads, since they will not considerably increase the moment capacity of the slab section. Some minimum steel, if provided in the bottom, will take care of possible stress reversals during earthquake.
If a cantilever beam is designed as a doubly reinforced one, then the (main)  compression reinforcement will be provided in the bottom.

E S Jayakumar



thank you for your reply sir.

If in A Singly Reinforced cantilever slab, the Depth of the slab is coming More, around 175 mm, will the Conventional Reinforcement provided at top would suffice?

how do we get to know for larger depth, whether or not Reinforcements required at Compression side of cantilever too. or up-till what depth for a cantilever slab normal Conventional Reinf at tension would suffice?
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es_jayakumar
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PostPosted: Mon Dec 16, 2019 10:45 am    Post subject: Reply with quote

Why cannot you support the cantilever slab by giving 2 cantilever beams provided at either lateral edges of it ? This will reduce the depth and reinforcement requirement of the slab, which will no longer be cantilever !

E S Jayakumar
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SHEKAHR_GOA
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PostPosted: Fri Dec 20, 2019 4:30 am    Post subject: Reinforcement At Compression(Bottom side) of cantilever Reply with quote

Taking this discussion further, compression steel in a cantilever slab will help in increase of stiffness of the slab and thus help in reduction of deflection.
I am of the opinion that cantilever balconies should be avoided by introducing a framing beam at the edge thus making the cantilever slab simply supported slab. This will reduce the slab thickness, decrease the dead load on the structure and will also help in structural integrity.

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Shekhar Panandiker

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PostPosted: Fri Jan 24, 2020 7:54 am    Post subject: Re: Reinforcement At Compression(Bottom side) of cantilever Reply with quote

SHEKAHR_GOA wrote:
Taking this discussion further, compression steel in a cantilever slab will help in increase of stiffness of the slab and thus help in reduction of deflection.
I am of the opinion that cantilever balconies should be avoided by introducing a framing beam at the edge thus making the cantilever slab simply supported slab. This will reduce the slab thickness, decrease the dead load on the structure and will also help in structural integrity.

Thanks & Regards,
Shekhar Panandiker

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Sorry for the late reply - I agree with the above post and want to put one point for further consideration. If we provide a cantilever slab (especially large cantilevers) without bottom steel, there is a small possibility of minor issues arising due to wrong sequence of deshuttering - if outer prop is left as such and inner props are removed, the slab will temporarily be simply supported. There will be no minimum reinforcement to take care of the tension in the bottom in such a case. This may not be a common occurrence and how serious it will be depends on the cantilever span.

Yours sincerely
S Arunkumar
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