Question

A smooth solid cylindrical utility pole of 30-ft in length and 8-inch in diameter is

subject to hurricane winds at 145 miles/hr. Air is at 32 F. Calculate:

a) The drag force on the pole,

b) The bending moment, and the bending stress at the pole base. Moment of inertia of the

pole is piR^4/4.

c) What is the frequency of the vortex shedding in Hz?

Answer 1

Calculate the drag force on the pole. Fo= par = P()r - 1 10.0810 21 32.2 NT 8 4112 (145x1.467) * = 19.86616 Calculate the bending moment and bending stress at the pole base. M=FoxL =(19.866)(30) = 595.98 lb-ft My = 4 1 MR)_4M 4(595.98 x12) TR = 142.28 psi TER 4 Calculate the frequency of the vortex shedding. SrxV_(0.2)x(145x1.467) f = 63.81H: D 8 12 Sr Strouhal number (0.2 for sub-critical flow)