${T^{\prime }}_{\text{d0}}$ (s)

3.00

3.70

4.40

5.10

5.80

6.50

Frequency (Hz)

1.3364

1.3248

1.3159

1.3091

1.3038

1.2994

Damping ratio (%)

7.17

6.86

6.53

6.21

5.92

5.67

${T^{\prime }}_{\text{d0}}$ (s)

7.20

7.90

8.60

9.30

10.0

Frequency (Hz)

1.2959

1.2929

1.2904

1.2882

1.2862

Damping ratio (%)

5.44

5.24

5.06

4.91

4.76