几何尺寸与公差论坛------致力于产品几何量公差标准GD&T (GDT:ASME)|New GPS(ISO)研究/CAD设计/CAM加工/CMM测量 - 查看单个帖子

how to find natural frequency of pole?
hi
i need to find the natural frequency of a tall, hollow steel round pole. basically it is a hollow steel pipe, 16" diameter.
does someone know the equation for this?
thanks
roark's formulas for stress and strain gives various formulae for a "uniform bar...vibrating along its longitudinal axis, upper end fixed, lower end free".
the fundamental frequency of a beam is (1/(2*pi))*sqrt(k/m). working this out for a cantilever with a uniform load (w)(selfweight) and a load at the end of the cantilever (p), the equation works out to f = 3.13 / sqrt(((p+0.236*w*l)*l^3)/(3*e*i)). p in kips, w in kips/inch, l in inches,
i'm glad you can answer this without knowing the fixity of the system.
cheers
greg locock
light pole, flag pole, these both seem to be cantilevered examples. usually anything that is not fixed at the bottom and free at the top is not called a pole.
cheers
thanks for the replies. actually it is a foul pole at a baseball stadium. it is indeed fixed at the base, and free at the top.
i am glad to see an equation. i used staad to output the frequency, but not having enough experience with this, i wanted some manual equations to compare with. it is not in seismic zone, and is to find the gust factor for wind loading, to determine if it is considered a flexible structure, with the higher gust factor.
it might be overkill for a foul pole, but the stadium is municipally owned, and they are a good customer of ours, so i don't mind the extra effort.
thanks for the rourk's tip, i have a copy (as all engineers should) but didn't think to look in there.
be very careful about the additional compliance introduced by the foundation.
cheers
greg locock
thanks for the input. i was already thinking about what type of foundation would be best. i was thinking that a drilled pier would probably give me the most stable base. i have loose sandy soils here. i am going to get with the geotechnical engineer for the job and see what he thinks as well.

2009-09-09, 05:47 PM	#1
huangyhg 超级版主注册日期: 04-03 帖子: 18592 精华: 36 现金: 249466 标准币资产: 1080358888 标准币	how to find natural frequency of pole how to find natural frequency of pole? hi i need to find the natural frequency of a tall, hollow steel round pole. basically it is a hollow steel pipe, 16" diameter. does someone know the equation for this? thanks roark's formulas for stress and strain gives various formulae for a "uniform bar...vibrating along its longitudinal axis, upper end fixed, lower end free". the fundamental frequency of a beam is (1/(2pi))sqrt(k/m). working this out for a cantilever with a uniform load (w)(selfweight) and a load at the end of the cantilever (p), the equation works out to f = 3.13 / sqrt(((p+0.236wl)l^3)/(3e*i)). p in kips, w in kips/inch, l in inches, i'm glad you can answer this without knowing the fixity of the system. cheers greg locock light pole, flag pole, these both seem to be cantilevered examples. usually anything that is not fixed at the bottom and free at the top is not called a pole. cheers thanks for the replies. actually it is a foul pole at a baseball stadium. it is indeed fixed at the base, and free at the top. i am glad to see an equation. i used staad to output the frequency, but not having enough experience with this, i wanted some manual equations to compare with. it is not in seismic zone, and is to find the gust factor for wind loading, to determine if it is considered a flexible structure, with the higher gust factor. it might be overkill for a foul pole, but the stadium is municipally owned, and they are a good customer of ours, so i don't mind the extra effort. thanks for the rourk's tip, i have a copy (as all engineers should) but didn't think to look in there. be very careful about the additional compliance introduced by the foundation. cheers greg locock thanks for the input. i was already thinking about what type of foundation would be best. i was thinking that a drilled pier would probably give me the most stable base. i have loose sandy soils here. i am going to get with the geotechnical engineer for the job and see what he thinks as well. __________________ 借用达朗贝尔的名言：前进吧，你会得到信心! [url="http://www.dimcax.com"]几何尺寸与公差标准[/url]