junichiro niwa, prof., dr. eng. department of civil engineering tokyo institute of technology...

Junichiro Niwa, Prof., Dr. Eng. Department of Civil EngineeringTokyo Institute of Technology

DISASTERS AND LESSONS OF CIVIL ENGINEERING STRUCTURES

BY THE GREAT EAST JAPAN EARTHQUAKE

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(1) The Great East Japan Earthquake occurred at 2:46 PM, March 11, 2011. (2) The epicenter was 24 km in depth from the seabed at 130 km east by southeast from Oshika peninsula.(3) The magnitude was 9.0, which is the highest magnitude ever recorded in Japan.(4) The epicentral area was very huge, about 500 km from Iwate Pref. to Ibaraki Pref. in a north-south direction, and about 200 km in a east-west direction.

　 Great East Japan Earthquake, March 11. 2011

(5) By the earthquake, huge Tsunami, which average height was near 10 m, (the maximum height was around 40 m) occurred, and the devastating disaster was caused.

Distribution of Main Shock and Aftershocks (Magnitude > 5.0)

■Very active aftershocks

■Wide range of aftershocks (from Iwate pref. to Ibaraki pref., 500km in N-S direction, 200 km in E-W direction)


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Characteristics of Earthquake Motion

■Very long duration might be a reason to increase the disaster of severe liquefaction.

-140

-70

0

70

140NS　 Max= 125 gal

-160

-80

0

80

160 EW　 Max= 157 gal

-80

-40

0

40

80

0 50 100 150 200 250

UD　 Max= 75 gal

1

10

100

1000

10000

100000

0.01 0.1 1 10

-1000

-500

0

500

1000NS　 Max= 818 gal

-800

-400

0

400

800EW　 Max=　　 617 gal

-400

-200

0

200

400

0 50 100 150 200 250

UD　 Max=　　 332 gal

1

10

100

1000

10000

100000

0.01 0.1 1 10

Duration of Earthquake Motion is very long.

Observed in Urayasu

Example of Kobe Earthquake, 1995

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　 Damages of Railway Structures

Surveyed Targets: (1) Shin-kansen structures(2) Bridges and piers of local JR lines in the coastal regions

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　 Damages of Railway Structures, Shin-kansen Structures

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Damages due to Earthquake Motion 新青森

盛岡

東京大宮

八戸

那須塩原

新幹線総合車両センター

小山

宇都宮

郡山

福島

一ノ関

北上

いわて沼宮内

仙台

土木電気

50箇所

0１箇所

　１箇所

　【凡例】

•In Tohoku Shin-kansen, damages happened in very wide range from Ohmiya to Iwate- Numakunai.

•In addition to civil engineering structures, many structures of electricity were damaged.

Distribution of Damages of Shin-kansen Structures

Morioka

Sendai

Tokyo

【 Legend 】Civil Electricity

50 places

10 places

1 place

Ohmiya

Iwate-Numakunai

Damages of RC Piers of Tohoku Shin-kansen Line:RC piers were damaged by the earthquake. This damage was very similar to that of 1995 Kobe earthquake.


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Since these piers are supposed to fail in flexure, sufficient shear reinforcement was not provided. However, within two weeks after the earthquake, sufficient shear reinforcement has been provided to these piers.


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Damage of RC pier

Damage of RC pier at the cut-off point of longitudinal bars.

Damage of PC girder

The end of PC girder was damaged near the support.

Left: Conventional Railway Viaduct (No damage at all because the newly developed seismic strengthening method after 1995 Kobe earthquake has been applied.)Right: Tohoku Shin-kansen Viaduct (Small damage was observed because only traditional seismic strengthening was provided.)


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Shin-kansen LineConventional Line

The collapse of PC electric poles occurred in wide area (around 800 poles). It delayed the recovery of Shin-kansen line.

Example of a PC electric pole with cracks by the earthquake.


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The concrete cover of a PC electric pole was completely peeled off.

A PC electric pole was replaced by a steel electric pole after the earthquake.


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Falling of ceiling boards of Shin-kansen platform at Sendai station by the earthquake.

Emergency stop of Shin-kansen train. No derailing at all.


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Completely destroyed Shin-chi station by Tsunami (Soma county, Fukushima Pref.).

Main girders were swept away by Tsunami (Tsuyagawa Bridge, JR Kesen-numa line).

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　 Damages of Railway Structures, Local JR Lines in the Coastal Regions

Isato-maegawa bridge (JR Kesen-numa line, Minami-sanriku town, Miyagi Pref.)

PC simple girder bridge. Piers were collapsed and girders were fallen down and swept away.

Completely collapsed pier. Abutment still remained.15


PC girders were completely swept away in the upstream of the river. One of the girder was completely turned upside down.

Isato-maegawa bridge (JR Kesen-numa line, Minami-sanriku town, Miyagi Pref.)

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Since the girder height is not high, the location of gravity center is not so high.

Pretensioned T-Shaped Girder

Post-tensioned T-Shaped GirderSince the girder height is high, the location of gravity center is also high.

After the flow of the girder, it may turn upside-down.

Tsuyagawa bridge (JR Kesen-numa line, Kesen-numa city, Miyagi Pref.)PC and RC simple girder bridge. Some of piers were already collapsed and girders were fallen and swept away.

However, RC girders still remained.

One of RC piers was failed with the break of longitudinal reinforcement. 18


The top of a RC pier was failed with the break of longitudinal reinforcement and the lateral beam was fallen down.

Tsuyagawa bridge (JR Kesen-numa line, Kesen-numa city, Miyagi Pref.)

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Several piers in the river were inclined. After 1978 Miyagiken-oki earthquake, girders and piers were strongly connected to prevent the falling down of girders. This time it worked negatively to increase the applying moment to piers due to Tsunami.


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Inclined RC piers still remained untouched in JR Tsuyagawa bridge.


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Main PC girder of Tsuyagawa bridge was swept away by Tsunami. Although it was a post-tensioned PC girder, it did not barely turn upside-down.


　 Damages of Road Bridges

Surveyed Targets: (1) Steel bridges(2) Concrete bridges

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　 Damages of Road Bridges, Steel BridgesShin-kitakami bridge (Road bridge, Ishinomaki city, Miyagi Pref.)

Steel truss girder bridge. Two spans of main girders were swept away by Tsunami.

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　 Damages of Road Bridges, Steel Bridges

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Structural members make a triangle. Normally it does not block the water flow of the river.

Truss Girder

Plate GirderSteel plate is provided at the web. Mechanism is very clear. However, it will block the water flow of the river.

Two spans of main truss girders were swept away in the upstream of the river (around 500 m).

　 Damages of Road Bridges, Steel BridgesShin-kitakami bridge (Road bridge, Ishinomaki city, Miyagi Pref.)

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Shin-kitakami bridge (Road bridge, Ishinomaki city, Miyagi Pref.)

Floated pavement slab of the bridge and other debris may block the water flow of the river. This is the reason why two spans of main truss girders were swept away.


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Two-span steel truss girders were completely swept away.

On the other hand, RC piers remained without any serious damage.


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Steel truss girders were found at around 500 m in the upstream of the river.


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Temporary steel girders have been erected to restore Shin-kitakami bridge to the normal state.

Koizumi bridge (Road bridge, Kesen-numa city, Miyagi Pref.)

Six-span steel plate girder bridge. Main steel plate girders were completely swept away.


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The device to prevent the falling of a girder remained. However, the device was not able to prevent the falling of a girder.

　 Damages of Road Bridges, Steel BridgesKoizumi bridge (Road bridge, Kesen-numa city, Miyagi Pref.)

The steel plate girders were found at around 350 m in the upstream of the river.

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Shishi-ori viaduct (Road bridge, Kesen-numa city, Miyagi Pref.)

This viaduct was submerged in Tsunami water.

Since girders were connected each other and piers were already strengthened, no serious damage was caused at all.

　 Damages of Road Bridges, Concrete Bridges

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　 Damages of Road Bridges, Concrete BridgesMatsukawa-ura bridge, PC Cable-stayed bridge (Road bridge, Soma city, Fukushima Pref.)

This bridge was attacked by Tsunami. Wave-dissipating blocks in the sea are found on the bridge deck after Tsunami.

In spite of Tsunami attack, the bridge was sound and strong enough.

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Utazu bridge (Road bridge, Minami-sanriku town, Miyagi Pref.)

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A1

A2

P1P2 P3 P4P5P6 P7 P8

P9P10

P11

To Sendai

To Kesen-numa

Pretensioned 5 girders

Post-tensioned 5 girders

国土地理院ホームページより

12-span PC girdersPretensioned 5 girdersPost-tensioned 3 girderswere fallen down

Post-tensioned2 girders

Fallen girders of Utazu bridge


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Post-tensioned PC girder turned upside-down. 　

Pretensioned PC girder was fallen down without turning.


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The device to prevent the falling of a girder was broken. It was not able to prevent the falling of a girder.

The main girder and concrete slab were fallen down together near the RC piers.

Since a RC pier was already strengthened, the damage was very slight.


From the damage of the pier, the direction of applying moment by Tsunami can be predicted.

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Fallen PC girders in the sea still remained untouched near the RC pier in Utazu bridge.

Numata bridge over railway (Road bridge, Rikuzen-takada city, Iwate Pref.)

Simply supported post-tensioned PC T-shaped girders were fallen down.

Situation of a fallen girder.

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The device to prevent the falling of a girder was not seriously damaged.

Since the anchor bars remained straight, the main girder was supposed to be floating and then falling.

Anchor bar

Numata bridge over railway (Road bridge, Rikuzen-takada city, Iwate Pref.)

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Other Structures

Surveyed Targets: (1)Disaster of Onagawa Town(2)Port structures(3) Floodgate(4) PC tank(5) Airport

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　Damages of Other Structures, Disaster of Onagawa Town by Tsunami

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Most of the town was damaged by Tsunami.

RC building was turned over by Tsunami.


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Many wooden buildings were completely swept away by Tsunami.

Even RC buildings were turned over by Tsunami.


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Trains were swept away and collapsed by Tsunami.

Another train car was shifted on the hill by Tsunami.

　Damages of Other Structures, Port Structures

Damages of breakwater and embankment by Tsunami (Tarou port, Tarou town, Iwate Pref.)

Breakwater and embankment were completely collapsed.

Breakwater of Tarou port was collapsed.

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Failure of huge concrete blocks of embankment (Soma port, Soma city, Fukushima Pref.)

Huge concrete blocks of embankment were collapsed and moved up on the apron deck of the port by Tsunami.


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Damage of port structures by Tsunami (Soma port, Soma city, Fukushima Pref.)

Collapsed quays in Soma port.


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Floodgate of Fuda-hama port PC curtain wall structure

Design Tsunami Height: T.P.+15.5 m(1896 Great Sanriku Tsunami was supposed.)Actual Tsunami Height 2011 ： around 17 m

　Damages of Other Structures, FloodgateFailure of concrete slabs of a floodgate by Tsunami (Fudai-hama port, Fudai village, Iwate Pref.)

PC curtain wall

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Failure of concrete slabs of a floodgate by Tsunami (Fudai-hama port, Fudai village, Iwate Pref.)

Tsunami over the floodgate suddenly dropped on the concrete slabs and destroyed the bridge.

　Damages of Other Structures, Floodgate

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　Damages of Other Structures, FloodgateFailure of concrete slabs of a floodgate by Tsunami (Fudai-hama port, Fudai village, Iwate Pref.)

The bridge was completely collapsed by the overflow of Tsunami. 51

　Damages of Other Structures, PC tank

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PC water tank and RC high pier (Iwate Pref.)

A RC high pier was damaged.

Shear cracks were initiated in a RC high pier after the earthquake, March 11.

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　Damages of Other Structures, PC tank

A PC water tank was fallen down from the top, but it did not crush.

PC water tank and RC high pier (Iwate Pref.)

A RC high pier was damaged by the earthquake, March 11.

Shear cracks were initiated .

Due to the aftershock of April 7, a RC high pier was completely failed.

　Damages of Other Structures, Airport

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Damage of Sendai airport by Tsunami (Natori city, Miyagi Pref.)

Sendai Airport

Sendai plain field was occupied by water caused by Tsunami.

Natori River

Damage of Sendai airport by Tsunami (Natori city, Miyagi Pref.)

Mud water accumulated on Sendai airport. However, Sendai airport has re-opened at July 25, 2011.

　Damages of Other Structures, Airport

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　 Summary(1)Major damages of civil engineering structures

were caused by Tsunami, not from the strong earthquake motion itself.

(2)Except the electric poles and another attachments, the damage of Shin-kansen was relatively slight.

(3)The damages of local JR line bridges and several road bridges were very serious. Many girders were fallen down or swept away by Tsunami. Several piers were also damaged by Tsunami.

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Thank you very much for your attention.57

DISASTERS AND LESSONS OF CIVIL ENGINEERING STRUCTURES

BY THE GREAT EAST JAPAN EARTHQUAKE

junichiro niwa, prof., dr. eng. department of civil engineering tokyo institute of technology...

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