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[amitavabh]

Dear Jagjit,

For designing underground tanks you can use following methods:

1. Use plate element and model it in Staad or other software. Provide soil spring support for base raft.

Calculate soil, water and surcharge pressure on wall. Calculate uplift due to water on raft. Use tank empty + soil around tank present condition. Then use full + soil absent around tank during test condition for worst load cases. If there is chember in the tanks then use alternate chember filled/empty etc. Then analyse.

Take output forces of plates. Select maximum force of "plate center stress summery" among the plates of each wall. Add torsional moment to the moment of both direction seperately. Then Design for this moment of each wall. Then take out bottom and top slabs. Calculate and check the crack width of walls/slabs against code values.

Use IS 3370 and IS 456 for refering to codal provision.

2. Calculate forces on tanks as told above. then use Roark's table to find out moment coefficients and then design for those forces. Check crack width.

Regards
Amitava Bhattacharjee
Kolkata

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Posted via Email

[maheshkkumar2002]

Dear Jagjit,

If you can give app size of tank it will be convenient to suggest. Becuase if the size of tank is large it can be designed as Retaining wall for water load and Soil loads. Base slab thickness can also be economised .You can use IS 3370 I, IS 3370 II, IS 3370 IV. It can be modelled in staad as explained by bhattacharjee.

Regards
Mahesh
Hyd

a_bhattacharjee[AT]yah... wrote:
Dear Jagjit,

For designing underground tanks you can use following methods:

1. Use plate element and model it in Staad or other software. Provide soil spring support for base raft.

Calculate soil, water and surcharge pressure on wall. Calculate uplift due to water on raft. Use tank empty + soil around tank present condition. Then use full + soil absent around tank during test condition for worst load cases. If there is chember in the tanks then use alternate chember filled/empty etc. Then analyse.

Take output forces of plates. Select maximum force of "plate center stress summery" among the plates of each wall. Add torsional moment to the moment of both direction seperately. Then Design for this moment of each wall. Then take out bottom and top slabs. Calculate and check the crack width of walls/slabs against code values.

Use IS 3370 and IS 456 for refering to codal provision.

2. Calculate forces on tanks as told above. then use Roark's table to find out moment coefficients and then design for those forces. Check crack width.

Regards
Amitava Bhattacharjee
Kolkata

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Posted via Email

[hgayake]

Dear Mr.Bhattacharjee,

Can you pls elaborate a bit more on adding the torsional moment? Should we not ensure whether it's a compatibility torsion or equilibrium torsion?

Regards
Hrishikesh Gayake
Civil & Marine Structural Engineer

.co.in wrote:
Dear Jagjit,

If you can give app size of tank it will be convenient to suggest. Becuase if the size of tank is large it can be designed as Retaining wall for water load and Soil loads. Base slab thickness can also be economised .You can use IS 3370 I, IS 3370 II, IS 3370 IV. It can be modelled in staad as explained by bhattacharjee.

Regards
Mahesh
Hyd

a_bhattacharjee[AT]yah... wrote:
Dear Jagjit,

For designing underground tanks you can use following methods:

1. Use plate element and model it in Staad or other software. Provide soil spring support for base raft.

Calculate soil, water and surcharge pressure on wall. Calculate uplift due to water on raft. Use tank empty + soil around tank present condition. Then use full + soil absent around tank during test condition for worst load cases. If there is chember in the tanks then use alternate chember filled/empty etc. Then analyse.

Take output forces of plates. Select maximum force of "plate center stress summery" among the plates of each wall. Add torsional moment to the moment of both direction seperately. Then Design for this moment of each wall. Then take out bottom and top slabs. Calculate and check the crack width of walls/slabs against code values.

Use IS 3370 and IS 456 for refering to codal provision.

2. Calculate forces on tanks as told above. then use Roark's table to find out moment coefficients and then design for those forces. Check crack width.

Regards
Amitava Bhattacharjee
Kolkata

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Posted via Email

[er.bhavin]

Dear Mr.Bhattacharjee,

When we model Base raft in STAAD, there are two issues regarding
supports.
1. Which kind of support should we provide. Plate Mat
Elastic Mat Spring Support. (I personally feel the plate mat option
gives better results when raft is modeled with plate element.)
2. When central portion of base raft is subjected to uplift
pressure in tank is empty condition, The spring support will resist that
根据他们的sti向上偏转ffness which is not the actual
case with soil.

Regards
Bhavin
_________

a_bhattacharjee[AT]yah... wrote:
Dear Jagjit,

For designing underground tanks you can use following methods:

1. Use plate element and model it in Staad or other software. Provide
soil spring support for base raft.

Calculate soil, water and surcharge pressure on wall. Calculate uplift
due to water on raft. Use tank empty + soil around tank present
condition. Then use full + soil absent around tank during test condition
for worst load cases. If there is chember in the tanks then use
alternate chember filled/empty etc. Then analyse.

Take output forces of plates. Select maximum force of "plate center
stress summery" among the plates of each wall. Add torsional moment to
the moment of both direction seperately. Then Design for this moment of
each wall. Then take out bottom and top slabs. Calculate and check the
crack width of walls/slabs against code values.

Use IS 3370 and IS 456 for refering to codal provision.

2. Calculate forces on tanks as told above. then use Roark's table to
find out moment coefficients and then design for those forces. Check
crack width.

Regards
Amitava Bhattacharjee
Kolkata

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mail, news, photos & more.

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Posted via Email

[Akshaya.Das]

Bhavin,

Reply to Point No.2

Use compression only spring to simulate soil. In case of uplift
corresponding soil spring will be inactive and will show zero support
reaction.

Regards,

Dr A K Das

-----Original Message-----
Message From bhavinpatel[AT]vms...
[mailto:bhavinpatel[AT]vms...]
Sent: Thursday, September 13, 2007 4:41 PM
To: Das, Akshaya
Subject: Underground Tank Design

Dear Mr.Bhattacharjee,

When we model Base raft in STAAD, there are two issues regarding
supports.
1. Which kind of support should we provide. Plate Mat
Elastic Mat Spring Support. (I personally feel the plate mat option
gives better results when raft is modeled with plate element.)
2. When central portion of base raft is subjected to uplift
pressure in tank is empty condition, The spring support will resist that
根据他们的sti向上偏转ffness which is not the actual
case with soil.

Regards
Bhavin
_________

a_bhattacharjee[AT]yah... wrote:
Dear Jagjit,

For designing underground tanks you can use following methods:

1. Use plate element and model it in Staad or other software. Provide
soil spring support for base raft.

Calculate soil, water and surcharge pressure on wall. Calculate uplift
due to water on raft. Use tank empty + soil around tank present
condition. Then use full + soil absent around tank during test condition
for worst load cases. If there is chember in the tanks then use
alternate chember filled/empty etc. Then analyse.

Take output forces of plates. Select maximum force of "plate center
stress summery" among the plates of each wall. Add torsional moment to
the moment of both direction seperately. Then Design for this moment of
each wall. Then take out bottom and top slabs. Calculate and check the
crack width of walls/slabs against code values.

Use IS 3370 and IS 456 for refering to codal provision.

2. Calculate forces on tanks as told above. then use Roark's table to
find out moment coefficients and then design for those forces. Check
crack width.

Regards
Amitava Bhattacharjee
Kolkata

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mail, news, photos & more.

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Everywhere

This e-mail and any attachment are confidential and may be privileged or otherwise protected from disclosure. It is solely intended for the person(s) named above. If you are not the intended recipient, any reading, use, disclosure, copying or distribution of all or parts of this e-mail or associated attachments is strictly prohibited. If you are not an intended recipient, please notify the sender immediately by replying to this message or by telephone and delete this email and any attachments permanently from your system.

Posted via Email

[er.bhavin]

Dear Dr. A K Das,

I have already tried that option of using compression only spring. I
gave uplift pressure in a separate load case and combine that in load
combinations. Now when I analyzed the model, the uplift load will not be
resisted by supports and hence it will give me large deformations
causing instabilities. Those large deformations when combined in load
combinations will give me very very large moments which is surely
impractical.
The other option is to apply uplift pressure and vertical downward
loads in one load case. This option may be workable but again there are
two issues.
1> For some load combinations we have to design the Structure/Raft for
no water pressure from bottom. In such case it is difficult and
confusing to define separate dead load case and analyze for that.
1> When there is a large raft with different size of panels, the no. of
iterations required for converging the reactions are very large which
cause very long time to analyze. I had analyzed such structure and it
took 24 hours to analyze even at the initial stage.

So compression spring is the best option but with the above issues.

Regards,
BhavinPatel

-----Original Message-----
Message From Akshaya.Das[AT]ake... [mailto:Akshaya.Das[AT]ake...]

Sent: 14 September 2007 17:44
To: Bhavin Patel
Subject: Underground
Tank Design

Bhavin,

Reply to Point No.2

Use compression only spring to simulate soil. In case of uplift
corresponding soil spring will be inactive and will show zero support
reaction.

Regards,

Dr A K Das

-----Original Message-----
Message From bhavinpatel[AT]vms...
[mailto:bhavinpatel[AT]vms...]
Sent: Thursday, September 13, 2007 4:41 PM
To: Das, Akshaya
Subject: Underground Tank Design

Dear Mr.Bhattacharjee,

When we model Base raft in STAAD, there are two issues regarding
supports.
1. Which kind of support should we provide. Plate Mat
Elastic Mat Spring Support. (I personally feel the plate mat option
gives better results when raft is modeled with plate element.)
2. When central portion of base raft is subjected to uplift
pressure in tank is empty condition, The spring support will resist that
根据他们的sti向上偏转ffness which is not the actual
case with soil.

Regards
Bhavin
_________

a_bhattacharjee[AT]yah... wrote:
Dear Jagjit,

For designing underground tanks you can use following methods:

1. Use plate element and model it in Staad or other software. Provide
soil spring support for base raft.

Calculate soil, water and surcharge pressure on wall. Calculate uplift
due to water on raft. Use tank empty + soil around tank present
condition. Then use full + soil absent around tank during test condition
for worst load cases. If there is chember in the tanks then use
alternate chember filled/empty etc. Then analyse.

Take output forces of plates. Select maximum force of "plate center
stress summery" among the plates of each wall. Add torsional moment to
the moment of both direction seperately. Then Design for this moment of
each wall. Then take out bottom and top slabs. Calculate and check the
crack width of walls/slabs against code values.

Use IS 3370 and IS 456 for refering to codal provision.

2. Calculate forces on tanks as told above. then use Roark's table to
find out moment coefficients and then design for those forces. Check
crack width.

Regards
Amitava Bhattacharjee
Kolkata

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mail, news, photos & more.

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Everywhere

This e-mail and any attachment are confidential and may be privileged or
otherwise protected from disclosure. It is solely intended for the
person(s) named above. If you are not the intended recipient, any
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Posted via Email

[lele_raj]

..alternatively, you can define it by a gap element, with very small amount of gap (say 0.00001). The gap will transfer compressive forces but will remain inactive under uplift.

Best regards,

Rajendra (Raj) Lele

P Please consider the environment before printing this e-mail or any attachment/s.

----- Original Message ----
Message From "Akshaya.Das[AT]ake..."
To: lele_raj[AT]yah...
Sent: Tuesday, 25 September, 2007 5:37:23 PM
Subject: Underground Tank Design

Bhavin,

Reply to Point No.2

Use compression only spring to simulate soil. In case of uplift
corresponding soil spring will be inactive and will show zero support
reaction.

Regards,

Dr A K Das

-----Original Message-----
Message From bhavinpatel[AT]vms...
[mailto:bhavinpatel[AT]vms...]
Sent: Thursday, September 13, 2007 4:41 PM
To: Das, Akshaya
Subject: Underground Tank Design

Dear Mr.Bhattacharjee,

When we model Base raft in STAAD, there are two issues regarding
supports.
1. Which kind of support should we provide. Plate Mat
Elastic Mat Spring Support. (I personally feel the plate mat option
gives better results when raft is modeled with plate element.)
2. When central portion of base raft is subjected to uplift
pressure in tank is empty condition, The spring support will resist that
根据他们的sti向上偏转ffness which is not the actual
case with soil.

Regards
Bhavin
_________

a_bhattacharjee[AT]yah... wrote:
Dear Jagjit,

For designing underground tanks you can use following methods:

1. Use plate element and model it in Staad or other software. Provide
soil spring support for base raft.

Calculate soil, water and surcharge pressure on wall. Calculate uplift
due to water on raft. Use tank empty + soil around tank present
condition. Then use full + soil absent around tank during test condition
for worst load cases. If there is chember in the tanks then use
alternate chember filled/empty etc. Then analyse.

Take output forces of plates. Select maximum force of "plate center
stress summery" among the plates of each wall. Add torsional moment to
the moment of both direction seperately. Then Design for this moment of
each wall. Then take out bottom and top slabs. Calculate and check the
crack width of walls/slabs against code values.

Use IS 3370 and IS 456 for refering to codal provision.

2. Calculate forces on tanks as told above. then use Roark's table to
find out moment coefficients and then design for those forces. Check
crack width.

Regards
Amitava Bhattacharjee
Kolkata

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mail, news, photos & more.

Why delete messages? Unlimited storage is just a click away.

Park yourself in front of a world of choices in alternative vehicles.
Visit the Yahoo! Auto Green Center.

Everywhere

This e-mail and any attachment are confidential and may be privileged or otherwise protected from disclosure. It is solely intended for the person(s) named above. If you are not the intended recipient, any reading, use, disclosure, copying or distribution of all or parts of this e-mail or associated attachments is strictly prohibited. If you are not an intended recipient, please notify the sender immediately by replying to this message or by telephone and delete this email and any attachments permanently from your system.

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