Question

Design dala Observalion deck mass m-25,000 k Danong ratio 0.5% Figure 91. Determine the equation of motion ofthe ๒wer teevibraorntheform (15 marks) mitt) + car)+xt)- where xt) is the horizontal displacement of the top of the tower b) Determine the damped natural frequency, fa (in Hz) of the tower (10 marks) ) A radar device, which inckdes a large rotaling eccentic mass, has been (30 marks) nstalled at the top of the tower Unfortunately, it has a trequency of rotation equal to the nalural frequency of he structure, which is exoted in resonance The amplitude of the force at is frequency is 400N Calculate the amplitude of the steady-state acceleration response due to d) I is proposed that a damping system is added to Ihe structure to reduce (15 marks) vibrations to an acceptable level of O 1 mi What equvalent damping ratio is requred to achieve this level of acceleraon? e) A SDOF system subjected to an initial disturbance (x0 0.03 m, %- 0.235 m/s) has a displacement response as shown in Figure Q1.2 (30 marks) Calculate the angular natural frequency of the system Calculate the damping ratio of the system (where A-0.03396 m) Approximate velocity and acceleration at t 0.412 ต.

Answer 1

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o ) 2 3 35)3 7165 MInn rn 25000 kg 冫0.529 λ«dlsel

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