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COOLING TOWER WIND LOAD CALCULATION

 
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manoj_pillai
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PostPosted: Sat Mar 31, 2018 1:58 pm    Post subject: COOLING TOWER WIND LOAD CALCULATION Reply with quote

what is the value of  Cf ( force coefficient ) for cooling tower?
referring to IS 875:2015 CLAUSE 7.4
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N. Prabhakar
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PostPosted: Mon Apr 02, 2018 5:41 am    Post subject: Reply with quote


Dear Er. Manoj Pillai,

For the design of Natural Draft Cooling Tower, Force coefficient  Cf  is not used to calculate wind pressure on the tower.  For wind pressure calculation on the tower, please follow the procedure given in IS: 11504, considering varying wind pressure along the circumference (using Fourier coefficients), and along height as per IS: 875 -2015.

I am attaching a Technical Paper, authored by me, which may help you to understand on the subject matter.

With best wishes,

N. Prabhakar, BE CEng(I) MIStructE (UK) MIE (Ind)
Chartered Structural Engineer
Vasai (E), Pin 401 208
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manoj_pillai
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PostPosted: Fri Apr 06, 2018 4:50 am    Post subject: WIND CALCULATION FOR COOLING TOWER Reply with quote

N. Prabhakar wrote:

Dear Er. Manoj Pillai,

For the design of Natural Draft Cooling Tower, Force coefficient  Cf  is not used to calculate wind pressure on the tower.  For wind pressure calculation on the tower, please follow the procedure given in IS: 11504, considering varying wind pressure along the circumference (using Fourier coefficients), and along height as per IS: 875 -2015.

I am attaching a Technical Paper, authored by me, which may help you to understand on the subject matter.

With best wishes,

N. Prabhakar, BE CEng(I) MIStructE (UK) MIE (Ind)
Chartered Structural Engineer
Vasai (E), Pin 401 208










Dear Sir,
            My cooling tower is 115 m high. And IS 11504-1985 (page 7, clause 5.1.3 and amendment no.1 October 1988) states that it cannot be applicable for above 100 m.
i have calculated gust factors but how to calculate the pressure
Is the formula mentioned below CORRECT ?
F= (Ce-Ci) x G x Ae x Pz


and how to calculate Ae ( frontal area)
is the value 1 for it ?
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manoj_pillai
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PostPosted: Fri Apr 06, 2018 3:14 pm    Post subject: wind load Reply with quote

Dear Sir,
             I have done following steps for calculating the wind load on natural draft cooling tower.
           1) I have also calculated Wind pressure pd as per IS 875
              2) as per IS 875  I have calculated Gust factors.
              3) as per IS 11504 I have calculated the circumferential values of wind

how to apply and what to apply ( I dont know the formula)on cooling tower elements ?

Kindly help me please.
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abhio
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PostPosted: Sat Apr 07, 2018 4:52 am    Post subject: Reply with quote

Dear Er Pillai,

Wind pressure calculated is to be applied to each element of the model according to the circumferential location of the element and its height above ground level.

Regards,

A S Oundhakar
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manoj_pillai
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PostPosted: Sat Apr 07, 2018 1:00 pm    Post subject: WIND LOAD Reply with quote

so we dont have to calculate gust ?

pressure on each pate  = circumferential coefficent x pressure from IS 875(Pz)


Is it right sir ?
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N. Prabhakar
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PostPosted: Sun Apr 08, 2018 6:49 am    Post subject: Reply with quote

Dear Er. Manoj Pillai,

By the way you are asking questions, you don't seem to have read my Technical paper Which I had posted on 2nd April 2018.

N.D. Cooling towers are not just simple cantilever type structures, and they are very large size 3-D type shell structures requiring finite element method of analysis, and design with  clear understanding of their structural behaviour.  In India, very few consulting and contracting firms, specialised in this type of structures, are doing the design and construction.  

Unless you are doing the design in one of these specilaised  firms where you would get certainly guidance from seniors in the firm, you would get the right experience over the years.   If you are doing for the sake of an academic interest, it would be of no use.

With best wishes,

N. Prabhakar
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