Vortex Shedding

Respected Sir,
I am doing a column of 24 meter height and 1 meter diameter. When i checked the vortex shedding box in Design Constraint, PVElite increases moment at basering at about 4-5 times because of which bolt area requirements, base plate and compression ring thickness increases about 4-5 times. My column design wind speed is 140.5 km/hr and in PVElite output the 1st and 2nd Critical speed worked out are 153.5 and 959.3 km/hr respectively. As it is clear by above data, column design wind speed is not matched with Critical Wind Speed then why the moment increases.

Please Clarify.
Warm Regards,
Saurabh Gajwani
Triune Projects Pvt. Ltd.
New Delhi (110044)

Dear Saurabh,

It may be that your vessel is not susecptible to vortex shedding. When the job was being analyzed, you may have seen the box that stated "Vortex Shedding will not be a problem and will cause excessive loads". It then goes on to ask if you want to continue to use those loads. If you say Yes, then the loads will be very high. Essentially, when this happens you are forcing the tower vibrate when it does not really want to. Try re-running the calculation and say no to the prompt and study the new results.

Sir


My coloum size is dia 90 meter and height 10 meter. When i analyse column in PVElite, the message come "Vortex Shedding will not be a problem and will cause excessive loads".
When I click Yes or No, it does not make any difference for column output. Please guide why this message is coming.