PSI - Issue 18

Bilal L. Khan et al. / Procedia Structural Integrity 18 (2019) 108–118 Bilal L. Khan et al. / Structural Integrity Procedia 00 (2019) 000 – 000 Γ = ̃ +

113

6

(13)

= 1 Γ − ̃ Γ

or

(14)

• As we have calculated the values of and , we can determine the value of mass of isolation layer : = √ + (15) • Three types of dampers with predefined damping ratio are used in this paper; High Damping Rubber bearing (HDRB: Damping Ratio=13%), Low Damping Rubber Bearing (LDRB; Damping Ratio=3%) and Lead Core Rubber Bearing (LCRB: Damping Ratio=25%) (Cheng et al., 2008; Desai & John, 2015). • By evaluating the , kb & cb, the response of base isolated structure is calculated by using state space approach in MATLAB. 3.3. Earthquake Excitations used for Dynamic Analysis: The earthquake excitations used for time history analysis are as shown in Table 2. Response of the building is investigated under near field and far field earthquake excitations to study the difference in the dynamic response of the structure. Near Field Earthquake epicenter from building structure is less than 25 km. Far Field Earthquake epicenter from building structure is greater than25 km (Chiou, Darragh, Gregor, & Silva, 2008). 1989 Lomaprieta Earthquake has magnitude of 6.9 on Richter scale, peak ground acceleration recorded of 4.35 m/sec 2 , and radius of 14.5 km falls in Near Field category (Chiou et al., 2008). Time histories of these earthquake excitations are presented in the figure 2 and 3 respectively. 1992 Landers Earthquake has magnitude of 7.3 on Richter scale, peak ground acceleration recorded of 1.46 m/sec2, and radius of 69.2 km falls in Far Field category (Chiou et al., 2008). Table 2. Model parameters of the structure (Pozo et al., 2016).

Peak Acceleration (m/sec 2 )

Peak Displacement (m)

Peak Velocity (m/sec)

Magnitude (M)

Earthquake

Location

Station No.

Radius (km)

1989 Lomaprieta, (Near Field)

6.9

Capitola

LP89Cap

14.5

4.35

0.292

0.05

1992 Landers (Far Field)

7.3

Armboy

21081

69.2

1.46

0.2

0.075

4

3

-3 Peak Ground Acceleration (m/sec 2 ) -2 -1 0 1 2

-4

-5

0

5

10

15

20

25

30

35

40

Time (sec)

Fig. 2. Time history: Lomaprieta Capitola Earthquake PGA 4.35m/sec 2 (Near Field).