Understanding the concepts on Degrees of Freedom
Procedure:
Step 1:
For mode 1:
We know that
=(0.334)+(0.641)+(0.895)+(1.078)+(1.173) x m 
Similarly
Mode 2 = m2 = 3.861m
Mode 2 = m3 = 3.861m
Mode 2 = m4 = 3.861m
Mode 2 = m5 = 3.861m
For the calculation of Ln:
L1 = ( 0.334 0.641 0.895 1.078 1.173 ) x 
L1 = 4.121
Similarly:
L2 = -1.297 m
L3 = 0.683 m
L4 = 0.381 m
L5 = 0.175 m
Now for the calculation of :
Similarly:
Γ2 = -0.336
Γ3 = 0.177
Γ4 = 0.099
Γ5 = 0.04
Now for the calculation of effective model mass Mn*:
Similarly:
M2 = -0.435 m
M3 = 0.120 m
M4 = 0.037 m
M5 = 0.008
To calculate model mass ratio:
Total mass of the building = m+m+m+m+m = 5m
For mode 1 = n = = 0.88
Similarly
Model 2 = n = 0.09
Model 3 = n = 0.02
Model 4 = n = 0.01
Model 5 = n = 0.002
First two mode are enough are to achieve the 90% we get 0.88 + 0.09 = 0.97
To calculate the base shear:
W.K.T
Vb1 = 4.389m x o.27g
Vb1 = 1.187mg
Similarly:
Vb2 = 0.327mg
Vb3 = 0.126mg
Vb4 = 0.039mg
Vb5 = 0.008mg
Average base shear by SRSS method :
Vb= 1.15 m