PSI - Issue 44

Masoud Pourmasoud et al. / Procedia Structural Integrity 44 (2023) 590–597

593

4

M. Pourmasoud et al. / Structural Integrity Procedia 00 (2022) 000–000

tested regarding the displacement increments mentioned in (ASCE 07 2022), section 17.8.2.2. However, the bearings’ specifications need to be fall within the allowable ranges under D M and 0.67D M . Table 3 demonstrates a sample tests’ results from isolator 7. The energy dissipated and its equivalent yield strength from prototype tests ( σ y-result ) is reported. Also, the yield strength regarding the proposed equation for the lead cores ( σ y-equation ) were obtained and compared with the test results. Both approaches represent a range of yield strength varies between 5.0 to 7.8, depends on the applied axial load and the lateral displacement.

        3.3

Table 1 Isolators’ mechanical specification and confinement category.

P cr -static

Confinement Category

(%)

α

Isolator

D b

D l

H l

IFR

(kN)

1

870

100

330

20703

1.45

2.27

MC

0.5

2

720

160

330

5154

2.06

5.5

0.37

LC

0.25

3

770

170

330

8029

1.94

5.4

0.36

LC

0.25

4

1020

170

330

25278

1.94

3.0

0.64

LC

0.25

5

1020

100

373

34797

3.73

1.04

3.6

HC

0.9

6

1220

120

373

71183

3.11

1.03

3.1

HC

0.9

7

770

85

326

13201

3.84

1.3

2.8

MC

0.5

Table 2 Isolators’ axial loads and lateral displacements.

Shear Strain

Gravity load

Max Seismic load

Min Seismic load

D M

0.67*D M

Isolator

(%) at D M

(kN)

(kN)

(kN)

1

3012

6349

530

390

261

150

2

720

2356

-171

264

177

102

3

1847

4074

-228

264

177

102

4

5141

14977

-343

264

177

102

5

5450

11278

500

341

228

126

6

10053

21932

500

341

228

126

7

1629

2667

530

248

166

102

It is notable that the yield strength from both approaches for each test are reasonably close so that under the maximum load and maximum displacement (PT-9) the σ y-result and σ y-equation are achieved 7.85 MPa and 7.58 MPa, respectively. The average of total yield strength ratios shows that the predicted σ y-equation have been 4.0% more than σ y-result . It worth mentioning that PT-12 shows a maximum difference between the test and the equation which might be due to the cyclic loading effect on the lead core strength as the isolator had experienced 33 loading cycles before PT-12.

Table 3 Tests’ results and yield strength comparison between prototype test and proposed equation – Isolator 7.

Isolator 7

Pcr (disp) (      

σy − equation σy − result 1.11

σ y result (MPa)

σ y equation (MPa)

Disp

Ah

Test

P (kN)

(mm)

(kN.m)

PT-4

1629

166

23.5

6.24

9412.03

0.17

6.94

PT-5a

1629

248

41.9

7.44

7602.64

0.21

7.08

0.95

PT-5b

1445

257

42.9

7.35

7408.21

0.20

7.02

0.95

PT-5c

1912

238

40.1

7.42

7819.75

0.24

7.19

0.97

PT-5d

2374

223

37.9

7.49

8147.44

0.29

7.36

0.98

PT-8

2667

166

25.8

6.85

9412.03

0.28

7.33

1.07

PT-9

2667

248

44.2

7.85

7602.64

0.35

7.58

0.97

PT-12

530

166

19

5.04

9412.03

0.06

6.55

1.30

PT-13

530

248

34.8

6.18

7602.64

0.07

6.59

1.07

Average

1.04