Understanding the concepts on Degrees of Freedom
Answer:
Given Data-
T1=2 sec 
T2=0.6852 sec
T3=0.4346 sec 
T4=0.3383 sec
T5=0.2966 sec
Adding first two modes Mass Participation Ratio we get,
=0.88+0.09
=0.97
To achieve minimum 90% of modal mass participation ratio, first two modes are enough.
| Sr,No. | Mode | Mn |
Ln |
γn | Mn* | Modal mass prticipating Ratio | VBn |
| 1 | n=1 | 3.861m | 4.121m | 1.067 | 4.398m | 0.88 | 1.187mg |
| 2 | n=2 | 3.861m | -1.297m | -0.335 | 0.436m | 0.09 | 0.327mg |
| 3 | n=3 | 3.861m | 0.684m | 0.177 | 0.121m | 0.02 | 0.126mg |
| 4 | n=4 | 3.861m | -0.381m | -0.099 | 0.038m | 0.01 | 0.039mg |
| 5 | n=5 | 3.861m | 0.175m | 0.045 | 0.008m | 0.002 | 0.008mg |