Question

2. The frame shown consists of a very stiff steel beam with a wide-flange beam (W33 X 200), welded rigidly to two vertical channels (C8 X11.5). Assume that the mass of the channels is small compared to the mass of the beam. The area moment of inertia of each channel about its centroidal bending axis is 1.3 in. An eccentric exciter weighting 50 lb is attached to the beam, which weighs 2,000 lb, and is used to excite the frame. The unbalanced weight of the exciter is 5 lb, and it has an eccentricity e of 2 inches. The maximum amplitude of the system was found to be 0.15 inches. Assuming no bending in the beam, and considering the channels to be completely fixed at C and D, determine, a) the natural frequency f of the lateral vibration of the frame and exciter as a system, b) the damping ratio of the system, c) the magnification factor at resonance. (10 pts) Jr 2000 b 0 ft E 30) psi 60 in 1,3 in.

Answer 1

Ecantaich e2 indku L- 60 inclu L3 K= 2166.66 JH/ n uin rn V2x 2166| 66 21 2 or Fy/k 2x2 166.46 x 2x ε

en aC M. mpl-tude 四.yo M. F. 12 g.gg