Failure Knowledge Database / 100 Selected Cases

Collapse of the Korea Seoul Seongsu Bridge〔 October 21st ( Fri ), 1994

Korea 〕

Masahiko KUNISHIMA (note of 1)
The central section of Seongsu Bridge, totaling over 48m in length which
was constructed across the Han River in Seoul, the capital city of Korea,
suddenly, collapsed during service. A bus and passenger cars, both in use,
fell in Han River under about 20m below, since it was the commuting time inthe early morning, and 32 people died, and 17 people were injured on thebridge. Following the investigation after the accident, the actual conditionof many "omissions" became clear.

Photo.-1. the situation right after the decay falling accident of Seongsu Bridge.
(Donation: Prof.Yozo Fujino, University of Tokyo)
1. Event
At 07:40 on October 21 (Fri), 1994, 48m of the central region of Seongsu
Bridge suddenly collapsed, which across Han River running Seoul the capital cityof Korea, urban bus and 6 passenger cars that driving down the bridge fell inriverabout 20m

below one after another. The fallen bridge girder which isupper part of pavement part did not sink in the underwater, since it was the dry
season and the water depth was 3-5m, and urban bus and passenger cars which fellin the top wrecked and they became rolling big disaster.

The victims were 17

day girls who on the bus and almost the other were workers driving to the office .
Seongsu Bridge have a lot of traffic volume which was a part of key component
1Failure Knowledge Database / 100 Selected Casesof road which connects the Konan district Seoul city heart division which isresidential section in the southern in Seoul City.

It is said that the traffic

jam arose, because especially, it was for commutation attending school hour inthe accident-generation, and because the rain fell, and that the rolling stock
was crowded.

Figure -1:

Position figure of Seongsu Bridge.

(Source: Nikkei construction)
2. Course
Seongsu Bridge has four lane (two lanes each way) roads of 1160.8m length and19.4m width.

Construction was started in April 1977, and it was completed inOctober 1979.

In Dong Ah Construction Ind. Co., it was Orderer Seoul City

consultant (designer) big consultant builder construction cost about 116 hundred
million Won (about 14 hundred million yen). It consists of steel truss digit of
the seven spans and simple steel and concrete synthetic column of 16 spans of
the before and behind. It is the 672m overall length in the steel truss digit
division where the accident occurred.

Five spans of the center are also one

span 120m on anyway, and the fixing support digit of the steel truss, whichissued bridge pier dry pitching of both sides, becomes the Gerber-structure thathangs and supports suspension digit of the center of the 48m length in thevertical member. Collapsing and fallen part was one of the suspension digits of2

Failure Knowledge Database / 100 Selected Cases

the center.
Seongsu Bridge it was comparatively new that it went to the 17 bridges towhich be built in Han River , and first traffic volume was utilized over the
double in the opening beginning, and standard rolling stock load were utilized
at not 18 tons expected in the design but 24 tons. In addition, Seongsu Bridge
the complaint was placed with that the swinging was intense in the running froma past, and the authorities in Seoul City carried out the repair work of theemergency in the night in accident the previous day.
There was the anxiety that the swinging was intense in the running from a paston Seongsu Bridge.

From the citizen, the complaint that the swinging of thesame bridge was intense recently was placed, and the authorities in Seoul City
carried out the repair work of the emergency in the night in accident theprevious day. As a testimony of the taxi-operator, there is some the report thatlevel difference was possible for the joint part (expansion joint) the previous
day 20 day and night same road surface 30cm.

Figure -2:

Schematic drawings of structural type of Seongsu Bridge.
(Source: Author made)3

Failure Knowledge Database / 100 Selected Cases

3. Cause(1) Bad welding of the suspension seems to be a main cause which member of theI-type cross section, which was hanging the suspension digit of the center fromthe steel truss.
That is to say, it was insufficient to carry out the edge

preparation of

the mate welding, and the except for surface part was the un- welding.
Therefore, the fatigue crack developed there, and it seemed to come to therupture.

That is to say, the cause of the accident is not corrode of the member

but poor of weld.

Then, this is not proven in the visual inspec tion.

Generally,

there might be a fault that was important for production and construction
management system that it should do the x-ray inspection and could not discover
the welding bad why on such weld zone minute.

Figure -3:

Weld zone minute of the suspension material.
(Source: Author made)(2)

Joint part an example showed in figure -3 and photograph -2 (the boltedjoint). The surface shape of fillet welding of photograph -2 is spot welding
like warty projection, and there is poor welding which is proven in the visualobservation that welding rod sufficiently does not dissolve.

The splice plateof photograph -2 there is a position where the volt has not been installed in
the volt hole of high-tensile bolt in which the position deviated; there wasomission construction which was proven in the visual inspection. Construction
management and inspection method in the construction of Seongsu Bridge seemed tobe remarkably slipshod, it was surveyed.

4Failure Knowledge Database / 100 Selected Cases

Photograph-2: Bolted
joint minute of the splice
plate (there is a position
where the volt has notbeen installed. (Source:Nikkei construction)(3)

Seongsu Bridge was sprayed Calcium chloride of 8 tons every year, which

scattered in order to prevent the road surface freezing, chloride ingress forthe cracks by poor weld or stress corrosion, and the corrosion of steel productmight be promoted.
(4) There is possibility to product unexpected partial crack in the steel
surface because in the cross-sectional shape of suspension steel product, coneangle (the relaxation curved surface) for easing stress concentration wasinsufficient.
(5)

Though there is no error at the content for the design, the immature

construction level may not be sufficiently assumed. Sophisticated technology,
skills, quality control, and inspection are necessary for the welding operation.
(6)

There were no technical standards on in service maintenance repair of

Seongsu Bridge.
（7)

For fiscal resource constraint (budget) of Seongsu Bridge it is in serv ice,the periodic check was not possible.
(8)

There were no survey on actual situation and inspecting standard on thechange (increase) of traffic load.
(9)

There was no technology (inspection) standard on maintenance and weldingof the bridge.
(10)

There was no tender contract system, which accurately selected thecontractor.
(11)

There was a social trend that however basic road of Seoul city facilities

vigorously early cheaply.

5Failure Knowledge Database / 100 Selected Cases

4. Immediate Action
Seoul City was not the last to presume cause of accident was that traffic
volume on the bridge increased, passage load became superfluous and thestructure was damaged in the storage of the fatigue. On October 22nd, 1994,
Seoul City released an interim report about cause of the accident that 1 insideof connection pin of 9 which connected collapsed suspension digit of the centerwith the fixing support digit of the steel truss broke, and other pins broke ina chain reaction by overload, and the suspension digit part in the center wasseparated and felt (mechanism reference of collapse and figure -4). The
corrosion of this pin and the weld zone was also confirmed. And, investigation
headquarters concerned police and prosecutor had grasped the abnormality of theweld zone of the bridge, since the August, 3 times, from the description of "therepair inspection diary" done the confiscation from Seoul east construction
office.
Same day and the prosecution in Korea arrested director’s construction work
office staff member of 5 persons of Seoul city road station east construction
work office which controlled the same bridge in the involuntary manslaughter
injury suspicion in the business. In spite of reporting with "the danger of thedecay is big", the periodic test of years 4 times for Seongsu Bridge is not
sufficiently carried out. And it is broken of the visual inspection in same year
February, and the inspection staffs finds corrosion and welding bad position of
the connection pin in the junction minute of the same bridge, and this isdisregarded, and it is the doubt neglected without taking measures of the safe
top which is appropriate accident 8 month close-at-hand.
On October 25th, 1994, the Korea Public Prosecutor's Office arrested roadfacilities section chief and facilities improvement chief clerk of the Seoul
City in the doubt of the involuntary manslaughter in the business.
On October 26th, 1994, Road Bureau length of the Seoul City was false official
document preparation, same exercise suspicion by the crime investigation team,and the pre- road facilities section chief was the involuntary manslaughter
suspicion in the business, and it was respectively arrested.

6Failure Knowledge Database / 100 Selected Cases

NorthSouth①Pin②Virtical welding③Separation ofsusupended truss

Figure -4.

The mechanism of a collapse.

Figure -4:

The mechanism of a collapse(Source: Nikkei construction)

5. Countermeasure
At this opportunity accident of Seongsu Bridge, the Korea nation got angry anddemand countermeasure to omission construction that spread in Korea.
It was decided that President Kim Young-Sam ordered general checkup of nationalroads and bridges and appointed the foreign special enterprise on the Korea
government for some main civil engineering works.
A consultant in the United Kingdom, Rendell Palmer and Triton (RPT) Co. madesuccessful bid the contract on integration and technical advice of the remedial
work of Seongsu Bridge.
And, it was redesigned (that existing concrete floor system is exchanged forthe steel plate floor, etc. ) in order to suit the design load that removes andincreased the suspension digit part in the center after the accident-generationof Seongsu Bridge for the inspection, in May, 1995， the Modern Construction Co.
received order at about 22 hundred million yen. In addition, the construction
began, and Seongsu Bridge was opened in July 1997 again for service.

7

Failure Knowledge Database / 100 Selected Cases

6. Generalization
Collapse accident of the Korea Seoul Seongsu Bridge which arose on October21st(Fri), 1994, the central region of the bridge suddenly collapsed over the48m length in service, and bus and passenger car under passage fell in Han River
under about 20m in respect of the bridge, and 32 persons died, and 17 persons
got injured. By the investigation after the accident, the actual condition ofweld zone the construction and construction management of bolted joint, and that
inspection method is remarkably slipshod and much omission became clear.
7. Knowledge(1)

Site welded by hands often warns well it. Don't trust it as a principle.

(2)

Penny wise and pound (human life) foolish. The infrastructure (the social

foundation facilities) works in the back.
(3)

The omission of the inspection is fatal.

(4)

The civil engineering structure issues the signal, before it falls through.

Don't miss it.
(5)

Slack off civil engineer is end of all.

8. BackgroundIn the Seoul City, during Korean War most part of bridges spanning the Han
River was destroyed. In 1988, mainly the Seoul Olympic Stadium new high-risecollective residential building street rapidly increasing, rolling stock passage
with the Seoul city also increasing, and enlargement demand of society for thebridge which spanning Han River and 2 bridges were carrying out construction in
those accident days.
17 bridges have been built over Han River, but in the investigation by theKorea society of Civil Engineers 1992, it says that the problem of the strain
coming out in concrete degradation of the underwater concrete part of the bridgepier, in the bridge in 11 inside in the whole bridge, had been indicated.

Theschedule, which starts the repair work by putting in the Seoul City, on thetotal amount of 4 billion Won in 1995, has been made.
9.

SequelIn Korea, the collapse accident of the bridge occurs after 1970's at eighttimes.
A collapse of the bridge, which is built in this inside in Han River of theSeoul City, is 3 times. In Korea, the accident of Seongsu Bridge became the past
maximum bridge accident. There is just an accident in which construction, bridgepiers of 10 and bridge girder part about 800m of the new fortune state Long
8Failure Knowledge Database / 100 Selected Cases

Bridge recently collapsed in July 1992. In the accident investigation which madeSeongsu Bridge which occurred for the stage in Korea this time frequently to bea beginning, the many people who make civil engineering technology( engineering ) and bridge technology ( engineering ) a specialty participated.
It is said that who left sense of crisis in the head of accident investigationand throw oneself into the breach were the elder people that studied andacquired civil engineering technology and bridge technology of Japan, even if
there are various and historical history to it. It is having told that theenergetic investigative action undermined the health and that the way of thesome person died with the completion of the accident investigation report fromoverwork.
10. On the SideBy self-confidence to 1990 ages in the part in our country Japan, the degree
faced telling technology and myth of the absolute safety for the engineering had
been faced such as Hanshin Earthquake, sodium leak nuclear fuel cycle Monju, JCO
criticality incident, and overlapping H2 rocket launch failure. Afterwards, thefollowing would be advocated: Technology and engineering based at last byextending twenty-first century that exceeded 2000 from the viewpoint of modesty
attitudes such as failure science and sociotechnique.
Decay falling of Seongsu Bridge was under usual common use condition in whichlarge swinging (vibration) by the natural condition (disaster) which remarkably
differs from the normal by the effect of strong wind by earthquake or typhoon
did not work. It was safely designed, as that for the accident, many engineersof Japan are on the bridge in Japan in 1994 usual common use condition, and thatit goes and consists, and that the decay falls is absolutely nonexistent, and it
commented, when the strict quality control had been done.

It was not a mistake,

until Toki-Messe communication deck bridge in Niigata City, August 2003 28
NISSIN lagoon Prefecture suddenly fell.
However, the accident in which it was homogeneous even in telling our country
with this accident by self-confidence did happen.
The rupture by welding bad which was the accident cause of Seongsu Bridge isgenerated cases in the temporary structure of construction site.
“It is a method for being convenient for the welding joining the steel producttogether.

So, sufficiently warn just it on the construction of the welding.

Especially that it is remarkably different from the case in which environmental
condition was controlled of the factory and is forbidden to trust the strengthof the joint at all, as long as it does not watch it by often warning the wholestory well, change of human factor are big construction site, and they weld it9Failure Knowledge Database / 100 Selected Casesby hands (not automatic welding).” The author who was a student with the bad
performance constructs it in the steel in 1968.

It was only matter by teachingin the lecture of Professor. Yoshie OKUMURA who is a big teacher of a fieldsteel structure, will be never forget (it has been learned).

(Note of 1)
Professor of Course of International Studies, Institute of Environmental Studies, Graduate
School of Frontier Science, the University of Tokyo
Professor of Department of Civil Engineering, the University of Tokyo (plural office)10