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50M DIA WATER TANK

 
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husseins20
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PostPosted: Mon Jan 27, 2020 1:19 pm    Post subject: 50M DIA WATER TANK Reply with quote

Dear Experts,

Can you please share your advise on the following situation:-

50m Diameter and 9m High RC Circular Tank. Resting on Ground.

Kindly advise if the wall is to be designed as proped cantilever and hoop tension or it will only have either of one only considering it H to D ratios.

Also some reference whereby similar tank example is furnished will be helpful

rgds
Hussein
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es_jayakumar
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PostPosted: Thu Jan 30, 2020 5:05 pm    Post subject: Reply with quote

Is your tank covered with roof slab at top ? Is the bottom of side wall constructed monolithic with base slab ? It will be ideal, if you can post a sketch of the layout of the tank showing the structural arrangements.

E S Jayakumar
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kawshik9
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PostPosted: Fri Jan 31, 2020 6:02 am    Post subject: Reply with quote

Er. Hussein,

1) In case base of tank is fixed, as the Diameter of tank is very large when compared to height of the tank, hoop stresses are very small and tank wall acts more like cantilever.

2) If the base joint is flexible, Hoop stress will be maximum at the bottom and it will govern the design.

3) As the tank is of huge size, its better to model it in STAAD or some other analysis tools and design accordingly.

I am sending water tank design chapter for your reference(Refer ch.22 page -11 for circular tank design)


Regards,

Ramakanth



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es_jayakumar
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PostPosted: Sun Feb 02, 2020 12:39 am    Post subject: Reply with quote

Er Hussain,
For furnishing a detailed answer, the structural arrangement of the tank is necessary to be posted. But, nothing is heard from you since. For large tanks (reservoir type), the side walls and base slab can be designed similar to cantilever retaining walls. Is the top of the tank is proposed to be covered with either dome with ring beam or slab & beam supported on internal columns ? This will determine if the top of the side wall is free or propped.

E S Jayakumar
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es_jayakumar
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PostPosted: Thu Feb 06, 2020 12:11 am    Post subject: Reply with quote

Er. Hussain,
In the absence of any communication from you, I have worked out stresses / BM for the tank assuming side wall fixed at base & free at top and 500mm thick wall, using STAAD and IS Code coefficients. This is purely for illustration purpose. You can modify the attached STAAD file to alter the support conditions and thickness of the wall, if necessary.
     
                                     STAAD                 IS 3370 : IV

     Max Hoop tension     865 kN/ m                850 kN/ m
     Max BM                     195 kN-m                       231 kN-m
     Max Shear                  161 kN/m                   207 kN/ m
               
You can refer the following worked out examples, for more details on design :
1. Ex18.3 of Reinforced Concrete Vol.II by HJ Shah (Charotar)
2. Ex.10.4 of Design of Reinforced Concrete Structures by ML Gambhir (PHI)
Also refer this link to SEFI  :
https://sefindia.org/forum/viewtopic.php?t=16484&postdays=0&postorder=asc&start=0&sid=d5436854d15af80207e0638ee9b05ea2

E S Jayakumar



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thirumalaichettiar
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PostPosted: Mon Feb 10, 2020 12:29 pm    Post subject: Reply with quote

Why not FLAT SLAB SYSTEM   can be used for the above tank since the dia is large say 50m and height is 9m?

T.Rangarajan
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es_jayakumar
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PostPosted: Mon Feb 10, 2020 12:45 pm    Post subject: Reply with quote

Certainly  !
But the questioner is silent, after raising the question !
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husseins20
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PostPosted: Fri Feb 14, 2020 9:28 am    Post subject: Reply with quote

Dear Eng. Jayakumar,

Apologies for the delay in response as was out of station.

Your valued input is really appreciated. The tank is eventually required to be covered. Cover can be shallow dome or beam slab.

rgds

Hussein
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es_jayakumar
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PostPosted: Thu Apr 16, 2020 4:10 pm    Post subject: Reply with quote

The tank in question is covered with roof slab. Support,  that permits rotation about horizontal axis, but restrains horizontal movement, is provided at the side wall top to simulate hinged top condition due to the wall's connectivity to  the relatively thin top slab. It is observed that there is no marked difference in the stresses :

                                    With top free                With top hinged

     Max Hoop tension       865 kN/ m                      790 kN/ m
     Max BM                     195 kN-m                       188 kN-m
     Max Shear                  161 kN/m                      161 kN/ m

Hence, it does not err much, if we assume top free condition for a circular tank with roof slab.

E S Jayakumar



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