Failure Knowledge Database / 100 Selected Cases

Collapse accident under New Haengju Bridge construction work
[Seoul City, Korea. July 31st, 1992]
Masahiko Kunishima (note of 1)
When New Haengju Bridge over the Han-gang River which connects the Jiangxi Wardin capital Seoul City with the Goyang city, Gyeonggi-do in Korea was under construction,
its 10 bridge piers and the bridge girder of 1020m length collapsed. The fault originatedin the cable-stayed bridge part in the center just before the completion.
Fortunately, no one was killed.

Photograph 1 the situation right after the collapse accident of New Haengju Bridge.

(Donation: Prof.Yozo Fujino, University of Tokyo)
1.

Event
At around 6:55 p.m, July 31st, 1992, New Haengju Bridge over the Han-gang River

which connects the Jiangxi Ward in capital Seoul City with the Goyang city, Gyeonggi-doin Korea collapsed suddenly (see photograph 1, figure 1).
Since the accident occurred after the work was finished and the workers had left thesite at 6:30 pm, no one was killed. It is said that the bridge under construction had no
specific abnormality right before the collapse accident. It brought about the damage ofthe various equipments of several billion won which had been temporarily put on thecompleted girder, and the extension for 2 years and 3 months of the construction which
had started in 1987 and planned to be finished in December, 1992, at the construction
expense of 17 billion won.
The New Haengju Bridge is a prestressed concrete(PC) box girder highway bridge of
1460m length and 14.5m of width which consists of 3 spans connected cable-stayed
bridge (100m+120m+100m) in the central part and multispan connected digits of the
60m span of both sides, as shown in figure 2. The substructure is composed of caisson
1Failure Knowledge Database / 100 Selected Cases

foundations or pallet pile foundations, bridge piers of reinforced concrete and the main
tower in the cable-stayed bridge part and abutments.
The features of the collapse situation was that the whole parts collapsed all at oncesince the entire part of 800m was a PC connected box girder structure and it was aunified structure, and that a form of destruction which is the breakage of the wholecross section occurred at various parts of the girders.

Length: 2.5km

Figure 1: Position of New Haengju Bridge.
2.

CourseThe PC connected box girders were installed by the extrusion method (Incremental

Launching Method). Each block was constructed in 20m lengths in the production
yards installed near the abutment of both sides, and were pushed out while being
connected one after another. It was planned to complete the section of 800m southfrom the northern abutment and the section of 660m north from the southern
abutment by the extrusion method.
Since the span of the superstructure (the bridge girder part) was 60m, 2 temporary2

Failure Knowledge Database / 100 Selected Cases

pillars (temporary piers) were installed in each of the 2 rather long spans at the cablestayed bridge section which were 100m and 120m long, and, in the each primary spansnear the production yards on both sides and in the span where the bridge girders fromboth sides meet, temporary pillars were installed.
One of the features of the wire of the PC cable-stayed bridge over the 3 spans wasthat it was not typical flexible steel cable, and that rigid PC members were used in it.
It was planned to install plain concrete at appropriate timing into the central part(20m long) of the central span within the 3 ones under the cable-stayed bridge for thecounterweight to suppress the negative cross sectional power, which is caused owing to
the length (120m) of the central span which is longer than the side ones of 100m
length. It is said that this plain concrete for the counterweight installed just before theaccident acted as an unexpected load on the temporary pillars which were placed at
the center span.
By the day of the collapse accident, the caisson foundations, the pallet pilefoundations, the abutments, the bridge piers, 2 main towers of the cable-stayed bridge
and the PC connected box girder part had been all completed except for the facilities
for military purposes. The installation of the cable for the main tower of one side wasfinished and the cable for the other was temporarily put on the surface of the bridge
girder. The concrete installation work of the joint with the bridge girder was carriedout while the required tensile force (prestress) was not supplied to the cable.
Then the collapse accident occurred, and the PC connected box girder part of about
800m length which was pushed out for the south from the northern abutment wascompletely destroyed, and the main tower of one side broke. The temporary pillars and10 piers were damaged heavily or destroyed (see Figure 2).

3

Fall

Slab

Failure Knowledge Database / 100 Selected Cases

Figure 2: Outline of the structure of New Haengju Bridge and the collapsed part
(Source: Author made from several materials)

4Failure Knowledge Database / 100 Selected Cases

3.

Cause
The collapse originated in the center span between 2 main towers of the cable-stayed

bridge, and the collapse of the temporary pillars which were set there was supposed tobe the direct cause (see Figure 3).
The connection performance of the PC connected box girders which were constructedby the extrusion method was considerably lowered (shear slip) by the installation workof the cable and the plain concrete. Therefore, the vertical load that acted on thetemporary pillars increased considerably. As the result, the load supporting capabilityof the temporary pillars was markedly weakened, and the unexpected force anddeformation acted on the PC connected box girders near the main towers and the cable,
and it led to the collapse of the main towers and the bridge girder. Since the whole PCbox girder section of 800m length was a connected digit structure, it is supposed thatthe big change of the load action condition by a collapse of one place triggered thecollapse of one after another place where the cross sectional power surpassed the yieldcapability of the member.

(3) Big vibration of(1) Abnormal loading

The superstructure

Cut

Cut

(4) Damage of main tower(2) TP4 depression

And collapse of girder

Figure 3: Collapse mechanism of the cable-stayed bridge part
(Source: Author made from several materials)

There might have been a failure in design and construction concerning the load
supporting performance of the temporary pillars. However, since the construction was
carried out without any prior examination about the effect of the load which arises
during erection on the temporary pillars, the cable, superstructure, and substructure,
it is evident that an excessive load acted and destroyed the members.
According to the accident report by Korea Soc. of Civil Engineering, the possible
accident causes were, improper span design, improper selection of the cable
construction method, impossible connection with an adjacent serial digit, improper
5Failure Knowledge Database / 100 Selected Cases

selection of the pier foundation construction method, improper design of the position
and the structure of the temporary pillars, shortage of the safety of the temporary
pillars in between the 2 main towers, shortage of cooperation between the design staffs
of the super/substructure and the cable-stayed bridge since they were separated,
incapability as a whole of the participants such as constructors, designers, andsupervisors, and frequent and complicated staff changes.
The quality of the ready-mixed concrete which was the main material of the PC
connected box girder bridge had been suspected to be bad, but it was proved not tohave any defect as concrete material by the test of the material extracted from the site.
4.

Immediate

ActionThe destroyed part of the bridge was removed and newly constructed.
The whole part of the PC connected box girders of 102m length, 1 damaged main
tower, and 12 piers were removed. In the demolition, breakers (large rock drill), thedropping steel sphere strike method, nonvibratile high temperature and the pressure
jet method, and wires-saw method, etc. were applied. The removal of the main tower
was determined by horizontal load safety test.
The remedial work was carried out by the joint enterprise of DS Co. from Germanyin the substructure and DRS Co. from USA in the superstructure under thoroughdesign checking and construction management, and New Haengju Bridge opened on
May 19th, 1995.
5.

Countermeasure
As a result of the technological study during the remedial construction, many designchanges were carried out.
(1) The cable of PC member whose rigidity was big was changed into flexible steel
one in order to improve the workability and reduce the dead load.
(2) They reduced the load on the main towers by changing the cable-stayed bridgepart (300m) to steel and concrete synthetic girder from PC connected box girder, andthe length constructed by the continuous extrusion method was changed to 420m.
(3) The foundations of the removed 12 piers were changed to the circular concrete
piles and their number and length was increased. The piers were strengthened byadding partitions to inside the hollow sections. Two of the three temporary pillars of
the cable-stayed bridge part were changed to permanent structures, and the other waschanged to steel from concrete.
The construction bureau of Korean government carried out safety checks on public
works and public facilities, and special inspections on bridges of the national roads.
The necessity of instituting law, regulation and technical standards on theconstruction management technology was shared in order to strengthen responsibility
6Failure Knowledge Database / 100 Selected Cases

and authority of the design and construction company, and in order to improve theconstruction supervision system.
A prior qualification check system (P.Q.) for judging the construction ability of thebuilders was introduced.
Remedies such as prior announcement of schedule price and basic research expenses,
a multiple schedule price system, installation and extension of tender and a contract
monitoring committee were introduced and the penal regulation on prior leakage oftender information was strengthened in order to prevent foul play in the tendering andcontract of public works.
6.

Knowledge
Loose application of new technologies is an origin of disaster.
Immature imported technologies can cause fatal accidents.
Supervising engineers who can understand and manage the whole of the process ofmaterial selection, designing and construction are necessary. However, there are manydifficulties in training them.
It is necessary to design considering the changes of loading conditions andstructural deformation caused by moving the construction equipment and thestructure during construction work.
Poor preparation and lack of risk management from greed are origins of major
accidents.
7.

BackgroundIn the atmosphere by the rapid economic growth in 1970's in Korea, the bridges

constructed in the capital city Seoul were criticized for lacking aesthetic sense in
1980's. The government officials who reacted to this criticism too sensitively applied
the PC cable-stayed bridge easily which was the latest method and the appearance
was graceful and airy, without grasping the safety and structural characteristics.
Since this was the first case of this method in Korea, the design and construction
specifications and technical standards of concrete cable-stayed bridge were
unimproved. But the government officials authorized the application of theunaccustomed method in order to improve the domestic technology without effectively
requiring the preparation of specifications for the new construction method. In
addition, the central design review committee installed in the Diet had showed only
general precaution and had not mentioned technical instructions under construction.
As a result, it was pointed out that the accident was caused by leaving thetechnological study on design and construction and evaluations of the safety to theforeign engineers. It is said the fatal factor that no one cared about the outrageous
behavior of leaving the cable of 120t weight made by PC member on the floor of the7

Failure Knowledge Database / 100 Selected Cases

connected box girder bridge since the Australian engineers didn’t see it as a problem.
Byuck San Construction Co., Ltd. which was the builder ordered the construction
completely from the subcontractors, since it did not own any required designing anderection planning technology. It used the drawing and specification and construction
plan which were required in tendering and contract as it had been made by thesubcontractors. The engineers of the Construction Promotion Public Corporation and
the Courtesy Technology Group who were the design and construction supervisors did
not have sufficient technological ability to manage the innovative PC cable-stayed
bridge.
The Korean construction industry at that time suffered supply difficulty of
construction material (inflow of bad material, shortage of such as cement, aggregate)
and labor shortage (inflow of inexperienced worker). And it is also said the cause of theaccident that they were rushing the construction of New Haengju Bridge since thecompletion was drastically delayed from the end of 1990 to the end of 1992, became of
the government budget shortage in addition to the above factors.
Since it was designed without considering the construction procedure, the design
and the construction procedure were frequently changed after the construction started.
The possibility of the excessive loading on the temporary pillars might have been
overlooked because of that.
In many cases of Korean public construction at that time, the orderers such as thegovernment, local governments, and public corporations customarily presented theaimed completion year to the constructors by deciding it without sufficientexamination about construction characteristics. Since the orderers set short design
period in order to move up the completion, the investigations of geology and grounddensity and measurements of land shape and rivers in the fields were rough. Therefore,
there were many cases in which there was no getting away from changing the design
after the construction had started.
In addition, it is said that the supervision and inspection by the orderer was only toview the appearance roughly.
8.

SequelIn Korea in the economic development which originated from the big success of theSeoul Olympics 1988, the serial collapse accidents by the beginning of 1990
represented by New Haengju Bridge highlighted the order looseness of the government
mechanism during the change period of the administration. The necessity of a big
reform to prevent foul play and corner-cutting in construction projects by thegovernment bureau was pointed out. However, this criticism has unfortunately been
proved right by the collapse accident of Seongsu Bridge 2 years later, and the floor
collapse accident of Sampoong department store in business.
8

Failure Knowledge Database / 100 Selected Cases

9.

On the Side
2 years after the New Haengju Bridge accident, a lot of articles were issued inJapanese newspapers and magazines and so on about the collapse accident of Seongsu
bridge which occurred during operation and killed many people. In the case of New
Haengju Bridge, news about it in Japan was very little because there were nocasualties. Descriptions in this paper were all translated from the Korean materials.

(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)9