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SUPPORT CONDITION

 
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shri shanmuga nandini A
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PostPosted: Mon Nov 21, 2022 12:30 pm    Post subject: SUPPORT CONDITION Reply with quote
what support should we assign for  UC Column base support in staad pro? when we have to consider fixed, pinned and fixed but (release moment in one direction )?
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vikram.jeet
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PostPosted: Tue Nov 22, 2022 3:51 am    Post subject: Reply with quote
Not clear on what UC  represents -

Column of buildings

Support Condition :
If strata Rocky, Hard  soil  -take Fixed

Medium or soft strata  -  hinged  is appropriate for gravity loading , but in  eartquake  fixity is available , in software it is not possible to include separate conditions,, hence fixed can be adopted..

For single col masts and towers - Fixed irrespective  of strata

Gravity loading moments at base are result of compatibility, and even slight rotation due to weak strata, cause this moment to cease.


However for equilibrium moments caused by wind EQ, especially on single column masts, there is no escape as str stability depend totally on this moment to be resisted.
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satishkemkar
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PostPosted: Tue Nov 22, 2022 6:49 am    Post subject: Reply with quote
UC represents universal column steel according to British standard
In staad , option "Fixed But " is available where you can release moment or force according to your choice

Thanks

Satish
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spsvasan
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PostPosted: Sun Dec 11, 2022 7:20 am    Post subject: Reply with quote
vikram.jeet wrote:
Not clear on what UC  represents -

Column of buildings

Support Condition :
If strata Rocky, Hard  soil  -take Fixed

Medium or soft strata  -  hinged  is appropriate for gravity loading , but in  eartquake  fixity is available , in software it is not possible to include separate conditions,, hence fixed can be adopted..

For single col masts and towers - Fixed irrespective  of strata

Gravity loading moments at base are result of compatibility, and even slight rotation due to weak strata, cause this moment to cease.


However for equilibrium moments caused by wind EQ, especially on single column masts, there is no escape as str stability depend totally on this moment to be resisted.



Dear Er.Shri ShanmugaNandini

I fully agree with Er.Vikram Jeet. Further, if the column is supported by 3 or more piles I will adopt fixed support condition. For single piles I adopt hinged condition. For double piles I adopt fixity along the pilecap and will release the base moment in the perpendicular direction

S.P.Srinivasan
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vikram.jeet
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PostPosted: Sun Dec 11, 2022 9:15 am    Post subject: Reply with quote
spsvasan wrote:
vikram.jeet wrote:
Not clear on what UC  represents -

Column of buildings

Support Condition :
If strata Rocky, Hard  soil  -take Fixed

Medium or soft strata  -  hinged  is appropriate for gravity loading , but in  eartquake  fixity is available , in software it is not possible to include separate conditions,, hence fixed can be adopted..

For single col masts and towers - Fixed irrespective  of strata

Gravity loading moments at base are result of compatibility, and even slight rotation due to weak strata, cause this moment to cease.


However for equilibrium moments caused by wind EQ, especially on single column masts, there is no escape as str stability depend totally on this moment to be resisted.



Dear Er.Shri ShanmugaNandini

I fully agree with Er.Vikram Jeet. Further, if the column is supported by 3 or more piles I will adopt fixed support condition. For single piles I adopt hinged condition. For double piles I adopt fixity along the pilecap and will release the base moment in the perpendicular direction

S.P.Srinivasan


Very rightly stated by Er SPSrinivasan saheb.

The above observation from my end were for isolated footings only without tie beams. In presence of tie beams in both dir, condition is fixed in all situations.
For Raft foundations  the condition is fixed irrespective of strata
Similarily for Pile foundations -col to pile cap is fixed in all situations

Single  pile case is very rightly pointed out by Sri SPS saheb.
Here if tie beams at pile cap level not there,, it needs to be hinged in dir where no tie beam run.
Twin pile cap - nicely explained

Further I feel that even in presence of plinth beams,, the compatibility moments at footing level are small,, and hence a fixed option is more close,, even if foundation tie beams are not present in isolated footings.
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