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FLAG POST

 
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husseins20
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PostPosted: Mon Dec 23, 2019 10:59 am    Post subject: FLAG POST Reply with quote

Dear All,

Can somebody please share a design example for Flag post.

A 12m high flag post is to be erected with a flag of 1m (H) x 3m (W).

i have tried using ANSI/NAAMM FP 1001-07, and i get section size of 168.3mm Dia and 5mm thick.

Is the above section going to be adequate or is it too big.


Advise on the above will be helpful.


rgds
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es_jayakumar
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PostPosted: Thu Dec 26, 2019 4:22 pm    Post subject: Reply with quote

I hope, the flag will not impart any torsion / BM / shear to the post, as the same will orient itself in the direction of the wind (parallel to wind). Thus, the flag post can be designed as a cantilever steel beam acted upon by wind load. The wind load can be computed using Table 25 of IS 875 (Part 3) : 2015 [Design Loads (Other than Earthquake) for Buildings and Structures Code of Practice Part 3 Wind Loads].
1.     Assume a trial diameter for the steel post (tube).
2.     Calculate the wind load per metre run using Table 25 of the Wind Code, for a circular section, by finding the appropriate value of Cf.
3.     Calculate the maximum BM for the post as a cantilever and design the section as a beam.
4.     If the self weight of the pole is significant, design as a beam-column, for the combined BM and axial load.

E S Jayakumar
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prakash chitale
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PostPosted: Fri Dec 27, 2019 8:30 am    Post subject: FLAG POST Reply with quote

It is correct size

On Fri, 27 Dec 2019, 12:22 pm husseins20, <forum@sefindia.org (forum@sefindia.org)> wrote:

Quote:
           Dear All,

Can somebody please share a design example for Flag post.

A 12m high flag post is to be erected with a flag of 1m (H) x 3m (W).

i have tried using ANSI/NAAMM FP 1001-07, and i get section size of 168.3mm Dia and 5mm thick.

Is the above section going to be adequate or is it too big.


Advise on the above will be helpful.


rgds
     



     


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es_jayakumar
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PostPosted: Sun Dec 29, 2019 6:59 am    Post subject: Reply with quote

A rough design of the flag-post in question, without considering the self weight of the mast & dynamic wind effects is attempted.  Experts please check it guide.

E S Jayakumar



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es_jayakumar
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PostPosted: Wed Jan 01, 2020 2:25 am    Post subject: Reply with quote

Dear Er.Hussein,
Please see the attached Article by Dr.N.Subramanian on the design of flag poles. As per this, the wind load on the flag is also to be considered in the design. An empirical formula for calculating the wind load on flag is also given. You can design your flag pole by taking into consideration the wind force on the flag also, using the mentioned formula. [ The quantum of this is found to be meagre, though]

Best wishes,
E S Jayakumar



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husseins20
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PostPosted: Fri Jan 03, 2020 8:54 am    Post subject: Flag Post Reply with quote

Thank you for your valued input.

Do we also need to satisfy l/r for this. since the pole will be as a cantilever, minimum r to satisfy le/r = 133mm thus 406.4 Dia 6mm thick would be required. Is this check also required to be satisfied?
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Dr. N. Subramanian
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PostPosted: Fri Jan 03, 2020 7:06 pm    Post subject: Re: Flag Post Reply with quote

Dear Er Hussein

Yes. you need to check the pole considering it as a cantilevered column.

see Clause 6.7 of ANSI/NSSMM FP 1001-07 Guide Specification for the Design of Metal Flagpoles, which can be downloaded from https://law.resource.org/pub/us/code/bsc.ca.gov/sibr/org.naamm.FP_1001-07.pdf
It also has sample calculations

Hope you also read my article, posted by my friend Er E.S. Jayakumar.

Best wishes
NS
husseins20 wrote:
Thank you for your valued input.
Do we also need to satisfy l/r for this. since the pole will be as a cantilever, minimum r to satisfy le/r = 133mm thus 406.4 Dia 6mm thick would be required. Is this check also required to be satisfied?
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es_jayakumar
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PostPosted: Sat Jan 04, 2020 1:26 am    Post subject: Reply with quote

Dear NS Sir,
Thanks for your guidance. The major vertical load on the pole is its own self weight and the eccentricity due to this will be practically nil. However, when it deflects laterally under wind force, then the resulting deflection will laterally translate the CG of the self weight ( at mid height) and this will cause some eccentricity with respect to its base. This has to be taken care of, I think.

Regards,
E S Jayakumar
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Dr. N. Subramanian
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PostPosted: Sat Jan 04, 2020 3:05 am    Post subject: Reply with quote

Dear Er Jayakumar

Yes. You are right. The document quoted by me also has sample calculations at the end.

Warm regards
Subramanian


es_jayakumar wrote:
Dear NS Sir,
Thanks for your guidance. The major vertical load on the pole is its own self weight and the eccentricity due to this will be practically nil. However, when it deflects laterally under wind force, then the resulting deflection will laterally translate the CG of the self weight ( at mid height) and this will cause some eccentricity with respect to its base. This has to be taken care of, I think.

Regards,
E S Jayakumar
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