m1 = 0.70 kip.sec2/ft I1 = 300 in4
m2 - 0.70 kip.sec2/ft I2 300 in*
m3- 0.65 kip. sec2/ft I3 - 280 in4
m4 - 0.55 kip sec2/ft I4 - 280 in4
![58_Find the modal frequencies.png](https://secure.tutorsglobe.com/CMSImages/58_Find%20the%20modal%20frequencies.png)
All columns have E = 29,030 ksi and L = 13 ft.
- Find the modal frequencies and mode shapes for the frame assuming the columns are fixed at the top and the bottom (i.t , the floors are rigid enough to inhibit rotation).
- Sketch out the first and third mode shape. Next to each mode shape, write the period for that mode.
- If you relaxed the assumption that the columns were rigidly fixed at the top and bottom, would the modal frequencies increase or decrease? Explain.