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husseins20 ...
Joined: 25 Apr 2013 Posts: 62
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Posted: Mon Jan 27, 2020 1:19 pm Post subject: 50M DIA WATER TANK |
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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 General Sponsor
Joined: 24 Nov 2011 Posts: 1408 Location: Cochin
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Posted: Thu Jan 30, 2020 5:05 pm Post subject: |
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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 General Sponsor
Joined: 28 Oct 2009 Posts: 16
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Posted: Fri Jan 31, 2020 6:02 am Post subject: |
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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 General Sponsor
Joined: 24 Nov 2011 Posts: 1408 Location: Cochin
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Posted: Sun Feb 02, 2020 12:39 am Post subject: |
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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 General Sponsor
Joined: 24 Nov 2011 Posts: 1408 Location: Cochin
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Posted: Thu Feb 06, 2020 12:11 am Post subject: |
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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 Silver Sponsor
Joined: 26 Jan 2003 Posts: 3554
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Posted: Mon Feb 10, 2020 12:29 pm Post subject: |
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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 General Sponsor
Joined: 24 Nov 2011 Posts: 1408 Location: Cochin
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Posted: Mon Feb 10, 2020 12:45 pm Post subject: |
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Certainly !
But the questioner is silent, after raising the question !
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husseins20 ...
Joined: 25 Apr 2013 Posts: 62
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Posted: Fri Feb 14, 2020 9:28 am Post subject: |
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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 General Sponsor
Joined: 24 Nov 2011 Posts: 1408 Location: Cochin
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Posted: Thu Apr 16, 2020 4:10 pm Post subject: |
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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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