Answer Happy

Mechanical Vibrations
The Department of Highways at Dale City put up a signage with a
thickness of ¼ inch at the corner of the highway. The steel post is
72-inch-high with a cross section of 2 in x ¼ in. and it can
undergo torsional vibration (about the z-axis) or bending vibration
(either in the zx-plane or the yz-plane). Determine the natural
frequency of the post in a storm during which the wind velocity has
a frequency component of 1.30 Hz. Let the density of steel be 0.283
lb/in3 and torsional stiffness of a shaft with a rectangular
section be:
3. The Department of Highways at Dale City put up a signage with a thickness of 14 inch at the corner of the highway. The steel post is 72-inch-high with a cross section of 2 in x 1/4 in. and it can undergo torsional vibration (about the z-axis) or bending vibration (either in the zx-plane or the yz-plane). Determine the natural frequency of the post in a storm during which the wind velocity has a frequency component of 1.30 Hz. Let the density of steel be 0.283 lb/in3 and torsional stiffness of a shaft with a rectangular section be: 14 [ 1 244 a k, = 5.33 ab G 1.63 (1 - )] 0 8.& in 20 STOP 30 in. 72 in. -2 in. (a) (6)