PSI - Issue 54

Koji Uenishi et al. / Procedia Structural Integrity 54 (2024) 67–74 Uenishi / Structural Integrity Procedia 00 (2023) 000–000

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4

a

b

Frequency [Hz]

50

10 5

1 0.5

0.1

600

1000

NS

0

]

-600

2

100

600

NS

EW

0

Doubtful

10

EW

-600

TD

Velocity [cm/s]

600

1

Acceleration [cm/s

TD

0

-600

0.1

0 102030405060

0.1

1

10

0.02

Period [s]

Time [s]

Fig. 2. (a) Seismograms recorded at the site JMA Kobe (latitude 34.6913  N, longitude 135.1772  E) for the Hyogo-ken Nanbu (Hyogo Prefecture

South), Japan, earthquake that occurred at 5:46 am JST on January 17, 1995, and (b) the related Fourier spectra (Based on the online data

provided by JMA, https://www.data.jma.go.jp/svd/eqev/data/kyoshin/jishin/). The latitude and longitude of the epicenter of the quake are

j = 7.3. The maximum accelerations in the NS, EW and UD directions at JMA

34.5983  N and 135.0350  E, with a focal depth of 16 km and M

Kobe with the epicentral distance of 16.5 km are 818.0, 617.3 and 332.2 cm/s 2

. Although there were verbal evidences of experiencing vertical

shocks on the onset of seismic shaking, the record in Kobe even at this short epicentral distance does not show signs of such vertical shaking

containing higher-frequency vibrations. Instead, like a usual earthquake, the horizontal shaking seems prevailing. However, we should note that

the detectability of higher frequencies or shorter periods of seismographs at that time is uncertain (modified after Uenishi (2021)).

a

b

Fig. 3. Astonishing earthquake-induced structural failures found (a) on the surface and (b) in the underground in Kobe in January 1995. In (a), the

reinforced concrete (RC) buildings near Sannomiya railway station looked completely safe at first sight, but the middle floor was vertically

compressed and it totally disappeared. In (b), at the Daikai railway station, the RC central columns supporting the roof at midspan collapsed

vertically and the road above sank, maximum 2.5 m, over an area of 100 m by 20 m (Photographs courtesy of Kobe City (a) and Professor

Emeritus Shunsuke Sakurai of Kobe University (b)).

method (NATM) as deep as 200 m below surface in the Rokko Mountains, the RC lining was damaged by some

vertical compression, and the subgrade jumped vertically about 10 cm and detached from the invert. But, strange

enough, no damage to the ceiling as well as no deformation of the invert and surrounding rock was found. These

peculiar tunnel failures in the town and in the mountains were the first ones that were not caused by instability near

the portal of the tunnel nor by movement of geological faults but may have been generated directly by seismic

waves. A structural failure akin to Bantaki was found in the Uonuma Shinkansen tunnel of the Japanese high-speed