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[Sunil Kumar Jatav]

Hello,

I am working on railway building project which need to be constructed near the building whose pile are already casted at site. I want to check the adequacy of that piles to take column loads of the new building. I have modelled the pile cap using the plate element in staad (model attached) and created spring pile support at pile location below 1.6 m. I am analysing the output from the staad, maximum reactions output is in the range of the individual pile capacity. I want to enquire whether it is the right way to
1. to model and analyse the structure in this type of situation.
2. How to check the pile cap whether it is safe in shear by making use of STAAD output result?

[rajancivildesign@gmail.co]

Based on reaction obtained from column, you know the worst case load that column has to carry. You know what is the pile capacity of single pile. Based on column load, the no. of piles required for each column is calculated. Then you have to check the adequacy of pile cap, pilecap size Based on shape of pile, depth Based on punching shear,and reinforcement Based on critical bending moment .Kindly refer any text book by RCC  by P.C.Verghese or foundation book by Verghese may be refer.
V.M.Rajan  
On Sun, 16 Jun 2024, 9:55 am Sunil Kumar Jatav, <forum@sefindia.org (forum@sefindia.org)> wrote:

[flowref]

Dear Mr Jatav 

It is clear that Pile Caps will bear the Thrust  of Columns and Piles will bear the Thrust of Pile Caps . 


For above , it is important to calculate Column Reaction . For this , you need to determine which Load Combination will be applied on whole Structure to calculate the Column Reaction . "IS" Standard says - unfactored load combination of LL+DL will be given on structure and then Reaction Force on Column will be calculated . 


If you take any other combination that above (like u add seismic loads or increase (LL+DL) by some factor of 1.25 or 1.5 etc , ) , then your Reaction forces will increase by high % necessitating more load carrying Piles or bigger Piles and so bigger Pilecap which will unnecessarily waste money . Many people do overlook this simple statement and they calculate Reaction Force of Columns based on Parameters prescribed for design of buildings with Seismic loads . 


Pls clarify the factor that u have taken to calculate Reaction Force


Rgds


Bajaj A K  


On Sun, 16 Jun 2024 at 09:56, Sunil Kumar Jatav <forum@sefindia.org (forum@sefindia.org)> wrote:

[flowref]

Dear Mr Jatav 

In your Staad Model , you have not used the Command to calculate "Reaction Force " . You should use your Load Combination 134 ( LL+DL ) and perform "REaction Load " . This will indicate the Thrust that each column will be subjected to .


Then , u can know nos of Piles and Dia of Piles etc . Then , u will know type of Pile Cap .


Hope it clarifies 


Rgds
 


On Sun, 16 Jun 2024 at 17:27, A K Bajaj <flowref@gmail.com (flowref@gmail.com)> wrote:

[azoom_kt]

Hello Sunil,

Have you found a solution for this issue? 

With regards,
Azoom

On Sun, Jun 16, 2024 at 9:56 AM Sunil Kumar Jatav <forum@sefindia.org (forum@sefindia.org)> wrote:

[Sunil Kumar Jatav]

Hello sir,

Yes, I get the solution of the above.

Thanks