Number of Cyclic Movements at Sealed Joints Relative to Story Displacement

The number of cyclic movements at sealed joints depends on the story drift size of the curtain wall panel. Table 3 shows the frequency of seismic occurrence in Japan during the past 75 years. Figure 1 shows the relationship between the seismic intensity scale and the frequency of seismic occurrence. The frequency of seismic occurrence remarkably varies according to locality in Japan. For intensities of 4 and lower 5, the

TABLE 2—Damage pattern and level of precast concrete curtain wall panel for estimated seismic intensities.

Degree of seismic intensity (Seismic intensity scale)

Story drift (R)

Damage pattern and level

Story drift to be carried out in this study (R)

Large earthquake (intensity 6)

*a-L

75

Fastener is broken.

Curtain wall panel is damaged or fallen down.

D 1

120 75

Fastener is damaged.

Precast concrete is damaged.

100

Moderate earthquake (intensity 5)

— SR < — 200 120

Sealant is damaged.

• D 1

300 200

Part of sealant is damaged.

200

Small earthquake (intensity 4)

K< —

m

No damage.

%

ii

© —

© |

TAB Ui 3—Frequency of seismic’ occurrence in Japan in the past 75 years.

JMA seismic intensity scale1* JMA seismic intensity scale5*

5 6 5 6

Prefecture®

4

lower

upper

lower

upper

Prefecture

4

lower

upper

lower

upper

Hokkaido

175

23

0

3

0

Shiga

14

3

0

0

0

Aomori

53

7

1

1

0

Kyoto

21

3

0

0

0

Twate

88

8

0

2

0

Osaka

13

1

0

0

0

Miyagi

54

14

0

3

1

Hyogo

29

3

0

1

0

Akita

16

4

1

0

0

Nara

14

4

0

0

0

Yamagata

19

3

1

0

0

Wakayama

31

2

0

0

0

Fukushima

64

13

0

0

0

Tottori

37

5

0

1

1

Ibaraki

105

8

0

0

0

Shimane

10

1

2

0

0

Tochigi

74

8

0

0

0

Okayama

8

2

1

0

0

Gumma

15

2

0

0

0

Hiroshima

13

3

1

1

0

Saitama

44

1

0

0

0

Yamaguchi

12

3

0

0

0

Chiba

89

6

0

0

0

Tokushima

13

1

1

0

0

Tokyo

44

3

0

0

0

Kagawa

20

1

1

0

0

Kanagawa

56

4

0

0

0

Ehime

15

3

0

0

0

Niigata

20

3

0

0

0

Kochi

16

5

1

0

0

Toyama

6

1

0

0

0

Fukuoka

5

0

0

0

0

Ishikawa

9

2

0

0

0

Saga

3

0

0

0

0

Fukui

19

3

0

1

0

Nagasaki

31

1

0

0

0

Yamanashi

32

3

0

0

0

Kumamoto

41

14

0

0

0

Nagano

94

11

0

1

0

Oita

25

4

0

0

0

Gifu

11

2

0

0

0

Miyazaki

42

9

0

0

0

Shizuoka

86

12

1

3

0

Kagoshima

84

8

4

1

0

Aicbi

19

2

1

0

0

Okinawa

80

11

0

0

0

Mie

30

4

0

1

0

*The number of earthquakes is shown for the entire prefecture in Japan.

bfhe JMA seismic intensity scale, which provides a measure of the strength of seismic motion, is measured with a seismic intensity meter. Because “intensity 5” or “intensity 6” did not necessarily correspond to the same degree of damage, “intensity 5й and "intensity 6“ have been divided into two scales: “intensity 5 Lower (4.5-4.9)1’ and "intensity 5 Upper (5.0-5.4)" and “intensity 6 Lower (S.5-5.9)” and “intensity 6 Upper (6.0-6.4)” respectively, since 1996.

longer the service life of a building structure is, the higher the frequency of seismic occurrence. In contrast, for intensities of upper 5 and above, the frequency of seismic occurrence is nearly the same, regardless of service life duration.

It is difficult to calculate exactly the number of cyclic movements of relative story displacement within the service life for each earthquake. Therefore, the number of cyclic movements at sealed joints within their service life is calculated under the following assumption. Generally, the relationship between range of movement at sealed joints and the number of cycles at sealed joints were evaluated by applying a loga­rithmic scale. It is expected that the number of cyclic movements of relative story displacement for one earthquake falls between 1 and 100 times. In our study, the relationship between one earthquake and the

FIG. 1—Relationship between seismic intensity scale and the frequency of seismic occurrence in each prefecture of Japan.

FIG. 2—Relationship of story drift and the number of maximum cycles of relative story displacement for sealed joints during service life in Japan.

number of cyclic movements of relative story displacement at sealed joints led to numerical formula—Eq 1—and the number of cyclic movements at sealed joints was assumed to be ten times for one earthquake.

«, = A X n[ (/=1/300, 1/200, 1/100) (1)

where:

n, = number of cyclic movements of relative story displacement in service life, n’j = frequency of seismic occurrences in service life,

A — constant.

Figure 2 shows the relationship between the story drift of curtain wall panels and the number of maximum cycles of relative story displacement at a sealed joint during its service life in Japan. The larger the story drift, the smaller the number of cyclic movements occurring during the service life. Cyclic movements at sealed joints at R= 1/300 occurred several thousand times; at R= 1/200, occurred several hundred times; and, at R= 1/100, occurred several tens of times during the last 75 years.