Answer Happy

PART C & D please
(6 marks) (c) The diagram below shows a tower structure supporting a cross-arm that carries a power transmission line. An inspection revealed that hairline cracks had developed in the cross-arm due to fatigue. It is suggested that these cracks may be caused by vibration due to vortex-shedding. A cross-arm 12 m long and outer diameter 300 mm is tested in a laboratory for transverse vibration and the first four natural frequencies are found to be 16 Hz, 27 Hz, 50 Hz and 116 Hz. For wind speeds ranging from 18 km/hr to 144 km/hr check if vortex-shedding frequencies correspond to any of the first four natural frequencies. (7 marks) (d) Evaluate the transverse force F acting on the cross-arm at a wind speed corresponding to the second natural frequency of 27 Hz. (4 marks) C= drag coefficient 1.0, p= fluid density = 1.23 kg/m² The Strouhal number = 0.2 3m om 3m Jm 6m Jm 구 300mm 0.0. O