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Home Work 1

Reports on Earthquake Engineering and Related Topics

Requirements for the Work no. 1

Write, in a text editor imposed format, a 5-15 pages research report regarding

one of the next topics:

1. Natural disasters (earthquakes, floods, tsunamis, typhoons, hurricanes, volcanoes, land-slides etc.) and their actions against constructions.

2. Structure of the Earth. 3. Causes of earthquakes.

4. Seismic areas of the world.

5. Plate tectonics. 6. Earthquakes mechanism.

7. Seismic waves.

8. Measurement of earthquakes. Seismic scales. 9. Geological history of the Earth.

10. Romanian earthquakes.

11. Measures to mitigate the earthquakes actions against constructions.

12. Measures to be taken by citizens to prevent the effects of earthquakes. Behavior during and after the earthquakes.

13. Large earthquakes of the world. Case study: Kobe, Japan, 1995, January 17.

14. Large earthquakes of the world. Case study: Sumatra-Andaman islands earthquake, off the west coast of northern Sumatra, 2004 December 26.

15. Large earthquakes of the world. Case study: Vrancea, 4 March, 1977.

16. Large earthquakes of the world. Case study: Northridge, USA, January 17,

1994. 17. Large earthquakes of the world. Cases of other important earthquakes.

18. Earthquake prediction.

19. Earthquake Engineering codes. 20. Soil liquefaction phenomenon during earthquakes.

21. Reminder from Structural Dynamics: Calculation of dynamic

characteristics using the flexibility matrix. 22. Reminder from Structural Dynamics: Calculation of dynamic

characteristics using the stiffness matrix.

23. Reminder from Structural Dynamics: Orthogonality properties of modes of

vibration. 24. Reminder from Structural Dynamics: Mass-normalization of modes of

vibration.

25. Reminder from Structural Dynamics: Free undamped vibrations of single

degree of freedom systems (SDFOS).

26. Reminder from Structural Dynamics: Free damped vibrations of single degree of freedom systems (SDFOS).

27. Reminder from Structural Dynamics: Forced vibrations of single degree of

freedom systems (SDFOS). Resonance. 28. Reminder from Structural Dynamics: Forced vibrations of multi-degree of

freedom systems (MDFOS). Flexibility matrix method.

29. Reminder from Structural Dynamics: Forced vibrations of multi-degree of

freedom systems (MDFOS). Stiffness matrix method. 30. Reminder from Structural Statics: Forces method.

31. Reminder from Structural Statics: Displacement method. Analytical form.

32. Reminder from Structural Statics: Displacement method. Cross form.

Notes: - The file CCE2007.doc from Appendix I is the template format for the

report. The students must know and understand the use of styles in

Microsoft Word.

- More or different topics might be imposed by the classroom coordinator. - Students might propose new or modified/improved topics.

- More than one student could focus on the same topic. However, the

reports must be different. - The work is normally given during the first week of the semester. The

time to solve the work is two weeks.

In what follows, an example regarding the topic number 13 (the case of Kobe 1995 earthquake) is shown. The first source for this report is the authors’ book

Earthquake Engineering.

“Computational Civil Engineering 2007”, International Symposium Iaşi, România, May 25, 2007

The Great Hanshin-Awaji Earthquake

Japan, January 17, 1995

Fideliu Păuleţ-Crăiniceanu 1Department of Structural Mechanics, Technical University, Iaşi, 700050, Romania

Summary

The Kobe earthquake was the most recorded and measured strong earthquake ever in the history of the humans. Based on previous experience, Kobe area from Japan

had been considered at a lower level of seismic risk. The very strong earth shaking

has surpassed any anticipation and surprised professionals. The Japanese Meteorological Agency (JMA) classified it as a 7-grade earthquake on the

Japanese seismic scale, the highest ever.

The records of JMA had shown for the first time peak ground accelerations that

reached 818 gal.

Material damages had been evaluated at a huge amount. Lost lives, however,

remain invaluable and irreversible.

KEYWORDS: Hanshin-Awaji Earthquake; natural disasters, construction

damages.

1. INTRODUCTION

The morning of January 17, 1995 has changed dramatically the life in the very

densely populated area of Japanese city of Kobe and vicinity.

The “Hanshin Dai Shinsai” occurred at 5:46 am and took the life of 6055 people and injured more than 30000 people. From the point of view of the number of

victims, the Great Hanshin-Awaji Earthquake is the second in the Japanese

(recorded) history, Table 1.

Table 1. Number of victims caused by major Japanese earthquakes

Earthquake’s name Date Magnitude Dead and Missing

1. Great Kanto 1923.09.01 7.9 142807 2. Great Hanshin 1995.01.17 7.2 6055

3. Fukui 1948.06.28 7.1 3848

4. Sanriku-Oki-Tsunami 1933.03.03 8.1 3008

5. Kita-Tango 1927.03.07 7.3 2925

2 F. Păuleţ-Crăiniceanu

Huge damages were induced in all kinds of structures, facilities, lifeline systems,

and reclaimed land. Hanshin Area, i.e. Kobe-Osaka area, was very affected by this

earthquake and the social and economic activity was practically stopped in Kobe

City. Meanwhile many citizens, about 300000, had lost their homes. Total loss is estimated at about $100 billion, Table 2 [1].

Table 2. Great Hanshin Earthquake. Overview of the damages

Cost to

rebuild/repair

(Billion $)

Number of Damages

Victims _ Dead 6055*

Injured 34626

Fire _ Number 531 Burned Area 100 ha

Building

(Housing, Store,

Factory)

63 Fully Destroyed 82105

Partly Destroyed 98892

Railway Collapse of Bridge and its deck 21

Derailment 15

Partly Destruction of Tunnel 5

Destruction of Station and Facility 40

Highway 22 Collapse of Bridge Deck 9

(including 6 collapses of pier)

Harbor Facility Destruction of Port 24

Life-Line Number of Interruptions and Destruction

Electricity About 1000000

Gas 8574000

Water Supply 6 1219000

Telephone 473000 circuits

Drain 60

Facility of Agriculture,

Rivers and Schools

5 _

TOTAL 96

*

Revised data from July 15, 1995

2. THE EARTHQUAKE CHARACTERISTICS

The coordinates of the epicenter were: N 34 36.4’ and E 135 2.6’ with a focal depth located at 14.3 km and a magnitude established to be 7.2 on Richter scale by

Japanese Meteorological Agency (JMA). The dislocation of the fault is estimated

to an average of 1m to at most than 2m. JMA had classified the ground motion of some areas of downtown Kobe at the intensity VII, the highest one, never used

“Computational Civil Engineering 2007”, International Symposium 3

before [2]. This intensity is equivalent to MM = X to XI. The measured moment

magnitude of the earthquake was Mw = 6.9, horizontal peak velocities reached more

than 100 cm/sec in central Kobe and horizontal peak acceleration of the ground

reached 818 cm/sec2 at Kobe Marine Meteorological Observatory [3]. Figure 1

presents a map with the position of the epicenter and the main horizontal

accelerations recorded on January 17 [7].

Figure 1. Epicenter's position

Many aftershocks occurred in the same day and the next days. The strongest one

was recorded 2 hours after the main shock and had a magnitude equal to 4.9 on

Richter scale [4]. The distribution of aftershocks in space and time is shown in Figure 2.

Figure 2. Distribution of aftershocks in space and time

Exa

mple

of

a f

orm

att

ed t

ext

report


In Figure 3, a plot of the N-S acceleration record of the Kobe strongest record is

shown.

0 10 20 30 40 50 60

-800

-600

-400

-200

0

200

400

600

KOBE NS 1995

818 gal

acce

lera

tion

(gal

)

time (s)

Figure 3. Kobe 1995 earthquake, NS acceleration record

Table 3 shows a selection of maximum acceleration recorded in some stations and

locations [4].

Table 3. Maximum Acceleration Recorded in Several Stations

Max. Horizontal

Acceleration

Max.Vertical

Accel.

Max. Vertical/

Max. Horizontal

Location N-S (gal) E-W (gal) (gal) ratio

Kobe University 269.8 306.3 446.5 1.46

Motoyama (Kobe) 421.0 774.9 379.3 0.49

Takeyama (Amagasaki) 271.4 321.5 327.9 1.02

Fukushima (Osaka) 180.0 211.05 194.8 0.92

Morigawachi (East

Osaka)

210.1 123.03 158.8 0.75

Abeno (Osaka) 217.4 226.4 136.2 0.60

Kobe Marine Meteo Obs. 818 617 332 0.40

Between the main characteristics of the near field ground motion it is worth to note the next three, [2]:

- short duration with few strong spikes

- arrival of primary vertical and horizontal motion at almost the same time - in reclaimed land, the acceleration response spectrum shows almost constant

strong magnification of the response for a large period interval.

- It must also be noted that the Hanshin area was known to be rather seismic

inactive before January 17, 1995. The strongest recent earthquakes, the 1944 Toh-Nankai earthquake with magnitude 8 and the 1946 Nakai-Doh


earthquake with magnitude 8.1, had epicenters in Pacific Ocean at distances

more than 100 km.

3. CAUSES OF DISASTER

Professor Masanobu Shinozuka from the Department of Civil Engineering,

Princeton University had described the Great Hanshin-Awaji Earthquake as “low

expectation, high damages”. In [5] two main causes of the disaster are identified:

1. The earthquake was off people’s attention and preparation:

- active faults were known to move once in several hundred years, but the

phenomenon was not expected at that time - Kansai Area had seldom been shaken by earthquakes, so people and experts

believed that the area was in a seismic inactive era

- old, rotted and weak houses could exist because of lack of even moderate shaken which could have prevented people. It is also believed that 1000

people died because of over-turned furniture

- even if the same building code is applied, the knowledge that an earthquake is

not probable to occur leads to less strength in structures - people and local government had no preparation for disaster.

2. In a high density city with complicated functions a strong and shallow

earthquake had occurred: - accelerations over 800 gal were recorded on the ground surface, exceeding the

design seismic load

- because Kobe is situated in a narrow belt between mountains and sea, there is no space for green belts and pools to prevent fires and food and water are not

reserved for emergency with traffic damage.

However, as many analysts observed, there were two elements that made

the effects to be not more extended: - the earthquake occurred early in the morning. At that hour there were few,

almost empty trains for transportation of people and the first Bullet Train

(Shinkansen) was not yet in operation. Also, the highways were with very light traffic. The most offices and companies did not start their activities.

- a very calm weather without wind. In case the wind had blown, the number of

casualties would have been much larger, especially because of the lack of

oxygen generated by fires (as was observed in case of Great Kanto Earthquake, in 1923).


4. LAND FAILURES

Kobe Port’s man-made islands Rokko and Port Island were most affected by the earthquake. Rokko Island has an area of 580 hectares and a perimeter of about 12

km and Port Island’s surface is 436 hectares and its perimeter is 16 km.

The earthquake effects on these islands consist in extensive liquefaction of ground

and large lateral movement of breakwater structures [4]. The breakwaters are concrete caissons, 10 to 14 meters width and were placed by completely excavation

of the soft clay in the seabed. The water level varies from 10 to 15 m.

Due to liquefaction a settlement had occurred. The settlement of the reclaimed granular fill was from 5 to 60 cm, relatively uniform so that structures located on

the islands were not very damaged, high rise building being built on long piers

beard on stiff sand. However, because of a movement of more than 2 m toward the sea of the concrete caissons and retaining walls, large container cranes in the yard

have suffered very heavy damages, even collapse.

Port of Kobe, the third largest port of Japan, which deals with 20% of the Japan

total cargo and posses one of major container facilities in the word [2], became non-operational. 179 of 186 berths at the port were shut down [3].

Landslides were also observed in many places. In Nikawa, close to a water cleaner

of the water service, a landslide killed 30 people and buried many houses. Other losses of life caused by landslides were not reported. An explanation could be the

low level of precipitation [5].

5. DAMAGES TO WOODEN STRUCTURES

In Kansai area old houses were built using wooden pillars and beams, jointed

without metal connectors. Pillars are not connected to the foundation with metals. The roofs are heavy and made of tiles tight with clay on the roof board. Some walls

are made of bamboo nets covered with clay and some are of thin wood-lath stucco.

Usually large openings are let in walls, for good ventilation during the hot summer.

The wood closed to the soil surface is rotted and suffered because of termites, [5].

More than 100000 traditional Japanese houses were severely damaged or totally

collapsed [2].

The main damages observed to wooden structures are titling, collapse of the first floor, and complete collapse. Causes of such damages are: material aging,

nonexistence of lateral force resistant elements (such as internal walls or bracing),

weak connections between vertical and horizontal elements, non-solid horizontal

diaphragms (as rigid floors or roofs), relatively heavy materials on roof, and impact forces of neighborhood [4].


Well designed and built houses, respecting the regulations and codes, suffered just

light damages. Prefabricated, mass-production houses, tested by government also

behaved very well. They have light metal roofs, strong bearing walls, good

foundations, and usually are equipped with air conditioners [6.7].

6. EFFECTS ON STEEL BUILDINGS

Although the damages and collapses of steel building structures were much more reduced compared with other type of structures, special problems occurred, [6].

However, the buildings built after the major 1981 revision of the building code

behaved, with some few exceptions, very well [2].

Very tall buildings, like Kobe City Hall, Kobe Hotel Oriental, were shaken but no

structural damages were reported. Some low and middle height structure collapsed.

The cause is a low structural quality, especially concerning the welded joints. Butt welding was often replaced by fillet-welding.

Figure 4. Brittle failure in columns

A careful attention was given to Ashiya Residential apartments that consist of big

frames, 14-24 stories, with truss beams and truss columns, built on reclaimed land.

High concern was raised because some of the column members were horizontally cut off, although no collapse occurred and was no losses of human lives. The

failure in hollow 5050 cm columns with plates of 50 mm thickness was brittle beyond any expectation without any traces of inelastic deformation [5], Figure 4.


7. DAMAGES TO REINFORCED CONCRETE AND COMPOSITE

BUILDINGS

The majority of aseismic designed buildings which were seriously damaged in the

Great Hanshin-Awaji Earthquake were concrete buildings. A large number of private residential reinforced concrete buildings had been overturned or collapsed

in the first floor while taller public housing, business and official buildings failed in

one of the middle floors, especially in downtown of Kobe, Sannomiya [4].

Many RC buildings were severely damaged but those with sufficient walls were quite safe. Pure rigid frames are not so suitable because the concrete cannot follow

the large deformations of the steel bars. The revised Japanese code from 1981

imposed additional design force to buildings with car-parking areas at the first floor, but the January 17

th earthquake proved the insufficiency of the revision.

Figure 5. Mechanism of girders’ falling dawn for a typical elevated highway

In the revised Japanese building code, the shear force is increased in the upper part of the building, while at the lower part it is decreased. The measure looks to be

justified because many buildings designed on the bases of the old code had

collapsed at their middle height.


In areas with intensity 7 about 7% of buildings designed on old code had been

ruined and only 2% of those designed on new code were damaged. The explanation

is that the pitch of hoop-bars had been narrowed from 15-20 cm to less than 10 cm

in columns and therefore their ductility were improved [5].

Reasons of the damages and failures are [4]:

- interaction between the different modes of vibration, causing the maximum

response in one of the middle floors - effect of construction method on the shear resistance of a floor, such as

interruption of concrete and reducing the column dimensions

- shortage of shear and internal walls or using many wide openings in walls especially in external walls

- combined effects of vertical and horizontal vibrations on the shear response of

the floors

- aging of materials - poor quality of concrete

- use of smooth bars for reinforcement

- non-suitable arrangement of stirrups and the distance between them.

Structures made from a steel skeleton and reinforced concrete are believed to be

very seismic proof but, in Kobe earthquake, they have shown damages mainly at

the anchorage to the RC foundation [5].

8. LIFELINE SYSTEM’S DAMAGES

The Great Hanshin-Awaji Earthquake produced severe damages to lifeline systems: gas, electricity, water and telecommunications.

More than 850000 of houses experienced stop of gas supply and the recovery of the

system was quite slow because of the special nature of this system [2]. The wall

meters, with automatic shut off at seismic movement, worked well [3].

9 cities and 5 towns faced water shortage [4]. From 1,355,600 households a

number of 930,000, suffered because of the water cut off. It took one month to

supply water to a population evaluated at 3,425,677 people. There were no damages to water tanks but the shortage of water lead to the spread and lengthening

of the fires. It was also reported no damages to dams. At the total of 7685 km

length of water pipelines a number of 5287 damaged locations where observed

almost at joints. Only 5% of the joints were aseismic designed joints. However, even to the joints improved to support 7-8 cm (and replacing old type designed for

only 3-4 cm) flexible displacement many damages occurred because the ground

displacement was in some places about 20 cm [4].


The electricity was cut off for a number of one million households. The next day

after the earthquake, January 18, that number was reduced to less than half [2].

After 6 days, the electricity for households was totally operational. 48 transform

stations, 38 transmission lines and 446 distribution lines had to be repaired [4].

The telecommunication system was also much damaged: 19300 lines were

interrupted because of cable break-up and other 265700 lines could not be used

because of electricity power supply failure. At the same time the number of calls was 50 times higher than usual. Damages were observed in many underground

tunnels or pipes used by telecommunication system. A telecommunication tower of

NTT (the national Japanese telecommunications company) located on the top of a building in Sannomiya, was tilted and buckled at the bottom [4].

9. FIRES

150 places [2] and over 1 million m2 [3] in Kobe area were affected by fires. Only

moderate wind was blowing in a period of few days after the earthquake and

therefore the extension of fires was limited. However the shortage of water and

also the traffic stoppage caused by the collapsed houses and narrow streets lead to difficulties in extinction of the fires.

10. ECONOMIC AND SOCIAL ASPECTS

The Great Hanshin Earthquake damages for Japanese economy are summarized in

Table 2. The area affected by the earthquake is 0.32% of whole land of Japan and

14.6% of the Hyogo Prefecture and it produces 3% of the nation production and 2/3 of the Hyogo Prefecture [2].

The huge loss of lives is mainly due to the collapse of old houses. Between the

dead people the majority was more than 65 years old. Rescue teams acted late, and, at the beginning, inefficient and not enough coordinated. Unprepared citizen

behaved with self-possessed manner [2]. Volunteers teams involved hundreds

thousands people, but these teams were organized many days after the earthquake.

However, their invaluable work was very important. Though the situation might require it, fast foreign aid was not accepted.

Because of the earthquake more than 300,000 survivors lost their houses and had

many difficulties in getting water, food and shelters, during a quite cold January. For more than 200,000 people there were built emergency shelters and then

temporary houses. Various psychological problems occurred linked with the long

stay in emergency centers. The temporary houses were not so popular because of

their location far from the city [2].


Reconstruction of the city is still a problem because of the citizen opposition to a

more clearly urban development. The majority of people wants to use the land they

possess for building new houses. As a consequence, a planning which includes

efficient disaster prevention is not possible to be applied. Larger streets and strong collective apartment buildings will be quite difficult to construct in Kobe.

11. CONCLUSIONS AND FINAL REMARKS

From a formal point of view the number of fatalities exceeding 100, the regulations

and codes must be re-checked. We also should consider that even when it is not

economical, compared to precious life, the price to increase structural safety is not too high [5].

The majority of analysts agrees over some aspects:

- re-evaluation of design seismic force, because of the large response spectral values observed

- re-evaluation of the seismic safety level to be conferred to each structure,

taking into account the effect of the loss of function

- more research must be done on evaluation of dynamic strength and ductility of parts and whole structures

- introduction of dynamic response analysis for the seismic design of a larger

category of structures - a broader use of seismic isolation devices as solution for energy dissipation

- effect of liquefaction and lateral spreading should be more studied.

As an example of countermeasures for preventing damages that could be induced by strong earthquake is summarized by the features of the UrEDAS

(Urgent Earthquake Detection and Alarm System) used by JR Company for safe

operation of Shinkansen lines.

The system is using a network of devices for early detection of seismic activity. Data obtained from these devices is processed in a UrEDAS center. The main idea

is to detect early P seismic waves, to establish the magnitude and the epicentral

distance and to issue an alarm before destructive S-waves arrive. The time for such computation was about 4 seconds. After the earthquake from Kobe, many

improvements were applied to the system and now the decisions can be drawn in 2

seconds from the P-wave arriving. In case that the seismic activity could be

dangerous, the Shinkansen trains operating in that area are stopped.


References

1. Obayashi Corporation Technical Research Institute - “Preliminary Report on The 1995 Southern Hyogo Prefecture Earthquake”, March 1995 (in Japanese).

2. Fujino, Y, Shoji, G. - “The Great Hanshin Earthquake - Seismic, Structural, Economic and Social Aspects”, Building for the 21st Century, Y.C. Loo (Editor), Proceedings of the Fifth Asia Pacific Conference on Structural Engineering and Construction, 25-27 July, 1995.

3. Matso, K - “Lessons from Kobe”, Civil Engineering, April 1995. 4. Kobe University Engineering Department - “Report on Southern Hyogo Prefecture Earthquake”,

February, 1995 (in Japanese). 5. Izumi, M. - “Structural Damage Caused by 1995 Great Hanshin-Awaji Earthquake - Japan”,

Building for the 21st Century, Y.C. Loo (Editor), Proceedings of the Fifth Asia Pacific Conference on Structural Engineering and Construction, 25-27 July, 1995.

6. Akiyama, H., Yamada, S. - “Damage to Steel Buildings in the Hyogoken-Nambu Earthquake”, Building for the 21st Century, Y.C. Loo (Editor), Proceedings of the Fifth Asia Pacific Conference on Structural Engineering and Construction, 25-27 July, 1995.

7. Honshu-Shikoku Bridge Authority - “Akashi-Kaikyo Bridge. Aseismic Design Specifications”, March, 1988 (in Japanese).

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