Recent Major Bridges in Korea
Hyun-Moo KOH
Professor
Jinkyo F. CHOO
Assistant Professor Konkuk University Seoul, Korea
Seoul National University Seoul, Korea
Hyun-Moo Koh, born 1952, received his BS and MS in civil engng. from Seoul Nat’l Univ. and his Ph.D. from the Univ. of Illinois at Urbana Champaign. He is currently chair of the Korean Group of IABSE.
Jinkyo F. Choo, born 1968, received his civil engng. degree from the Univ. Libre of Bruxelles and his Ph.D. from Seoul National Univ.
Summary
During a relatively short period, bridge technology in Korea has recognized outstanding development. Owing to the governmental policy aiming to achieve balanced regional development, unprecedented bridge construction activities are conducted in the peninsula, especially in the southwestern coast to link some of the 3,000 islands with the mainland. Korean bridge engineers are now designing and constructing bridges using domestic technology, which has today reached a level enabling to realize the erection of numerous sea-crossing bridges counting among the longest in the world like Incheon cable-stayed bridge (main span 800m) and Gwangyang suspension bridge (main span 1545m). This paper reviews the evolution of modern bridge construction in Korea and presents major bridges recently erected or to be built. R&D programs dedicated to the advancement of bridge technology are also introduced.
Keywords:bridge technology; sea-crossing bridges; cable-supported bridges; R&D programs.
1. Introduction
Despite of its short history of 40 years, the Korean bridge technology recognized outstanding development. The construction of bridges was at first involved as social infrastructure supporting the series of 5-year plans of the governmental policy since 1962 aiming to boost the economy of the country. As a result, the bridge stock of the peninsula increased from 9,322 bridges in 1970 to 22,937 bridges in 2007 and the corresponding developed length extended
Fig. 1 Number of bridges built by decades in Korea [1]
from 268km to 1,987km [2].
It is noteworthy that even if the developed length of the bridges multiplied by 5 times, the bridge stock only doubled. This means that Korean bridge engineering has realized remarkable progress in the domain of long-span bridges such as cable-supported bridges. In a short delay, Korea will have a cable-stayed bridge, Incheon Bridge (80+260+800+260+80m) that will rank at the fifth position among the longest cable-stayed bridges in the world, and a suspension bridge, Gwangyang Bridge (main span: 1545m), that will be the third longest bridge in the world at its completion in 2012.
The preference given to cable-supported bridge can be attributed to the topography of the Korean peninsula. Seventy percent of the country is composed of mountainous areas and the coastal regions are surrounded by 3,174 islands, which represent 3.80% of the territory with 0.65% of the population. Most of these islands being inhabited, their connection with the mainland is of primordial importance for the balanced regional development and preference is indeed given to cable-supported bridges in order to secure navigational channels (Fig. 2).
The construction of bridges is thus a necessity that will bring multiple benefits. In a social point of view, about 90% of the 3,174 islands of Korea are gathered in the southern and western coastal areas of the peninsula, of which most are located within a distance of 1km from the continent. However, the aging and emigration of the working population to big cities and the poor accessibility are accelerating their desertion. In an economical point of view, it becomes obviously necessary to prepare for the future tourism inflow and economic revitalization of remote areas through
Fig. 2 Overview of the islands of Korea by province
the construction of seashore road belts conducted by the governmental plan.
The scenes offered by the southern and western coasts will be a very profitable source of revenue for these regions. The construction of bridges will also reduce significantly the large deviations caused by the sawtooth coastline, and improve the accessibility and transportability of goods fabricated in the neighbouring industrial complexes [2,3].
The bridge stock will grow continuously through the restless sea-crossing bridge construction activities in the southwestern coast, especially in the Province of Jeollanamdo located in the southwest of Korea and bounded on the west by the Yellow Sea and on the south by Jeju Strait. Almost 2,000 islands of which 75% are inhabited are scattered along the 6,100km of its coastline. The plan of the provincial government is to provide a total of 103 bridges to link major islands. Among these, 33 bridges have already been
- completed,
- 21
- are
- under
Fig. 3 Sea-crossing bridge construction activities in Jeollanamdo Province
construction and 48 are under project (Fig. 3).
At completion of these bridge projects, the southwestern coast of Korea will become a museum of bridges with all types of structures from simple girder bridges to world-ranking suspension bridges. The following intends to review briefly the 40 years of the history of bridge in Korea with focus on sea-crossing bridges so as to highlight major recent bridges that have been or are being constructed all over the country. Recent national R&D programs of the Ministry of Land, Transport and Maritime Affairs (MLTM) and in-house programs dedicated to the advancement of bridge engineering and design are also introduced.
2. Evolution of Modern Bridges in Korea
Construction has been the backbone of the economic development of Korea and, bridges in the transportation network played a critical role in the realization of the “Miracle on the Han River”, which is the astonishing period of rapid economic growth that took place from 1961 to 1997. The Miracle on the Han River that started from Seoul to propagate over the whole country enabled Korea to propel as the 12th largest economy in the world after the ravages of the Korean War (1951-1953).
Korea achieved its transformation from agrarian economy to a modern industrial power within three decades, which other industrialized countries took almost a century to achieve, owing to the succession of 5-year development plans since 1962 (1962-1996). These plans were established by the government by identifying specific areas for outward-oriented national development driven by the assumption that economic growth and competitiveness cannot continue without breakthroughs in science and technology. Accordingly, social infrastructures including roads, railways, airports, harbours and bridges were restlessly built to support the industrialization process as well as the stabilization process for the regional balanced economic development. Excluding the bridges built before the Independence and the creation of the Republic of Korea, four major periods can be distinguished in the evolution of modern bridge technology in Korea, which correspond roughly with the series of 5-year economic plans of the government.
2.1 First Generation of Sea-Crossing Bridges in Korea (1962-1990)
The first generation of sea-crossing bridges in Korea corresponds to the introduction period of foreign technology and grew along with the industrialization boom of the country until 1990. At the time, the government poured huge investments for social overhead capitals (SOC) and construction was funded essentially through public loan. Various types of bridges were built in records of time but the need for rapid construction and the lack of skill often resulted in poor quality of construction. The collapse of Sungsu Bridge in Seoul in 1994, only 15 years after its opening to traffic in 1979, is a sadful example of unskillfully erected bridges at the time. In addition, the design of most of the bridges of the first generation was relying on foreign technology.
Besides, this period corresponds also to the introduction of cable-supported bridges in Korea with Namhae Bridge, the first suspension bridge in Korea. Namhae Bridge completed in 1973 after 5 years of construction is a three-span suspension bridge with a main span of 660m (128+404+128m) and stiffening girders composed of welded steel boxes. Thereafter, several cable-stayed bridges were built like the first Jindo Bridge (70+344+70m) and Dolsan Bridge (85+280+85m) in 1984 (Fig. 4).
Fig. 4 Views of Namhae Bridge, Jindo Bridge (front: 1st Jindo Bridge, rear: 2nd Jindo Bridge) and Dolsan Bridge
Together with the increase of the bridge stock, Korea experienced also tremendous increase of traffic. The number of vehicles registered in Korea today has already exceeded 16 million units. From 1970 to early 2000s, the total number of vehicles multiplied by 120 and the number of trucks mutiplied by 60. To worsen the situation, the dimensions and weight of trucks increased dramatically. However, even if the bridges designed at the time were applying truck design load DB-18 (total weight of 34tonf) with consideration of the future increase of traffic volume and vehicle loads, design could not predict such exceptional increase of vehicle. For example, the traffic load of Namhae Bridge has been controlled and limited to 32.4t since 2003 after 30 years of operation due to the appearance of fatigue cracks in the girder generated by the incessant crossing of heavy trucks [4]. The first Jindo Bridge, the first cable-stayed bridge in Korea and also the longest cable-stay span outside Europe at its completion in 1984, was also designed with respect to design live load DB-18. Similarly to Namhae Bridge, the bridge was subjected to truck loads exceeding the design load and the governmental authorities decided to improve the load carrying capacity of the existing bridge while erecting a twin bridge (Fig. 4) designed for vehicle load of DB-24 and DL-24.
2.2 Second Generation of Sea-Crossing Bridges in Korea (1991-1999)
The second generation of sea-crossing bridges was built for the development of islands. During this period, the domestic bridge engineering started to secure self-reliant technology for FCM (free cantilevering method) and steel box bridges. Bridges were essentially designed in terms of functionality and economy, which may explain the absence of construction of cable-supported bridges in 1990s. Another factor was the financial crisis that hit the country in 1996 and called the implementation of IMF-mandated reforms in 1997. Fig.5 shows representative sea-crossing bridges of the second generation. This second generation can be seen as the period of technology imitation characterized by the lack of originality in design.
Fig. 5 Views of Onnam Bridge (1996), Seonammun Bridge (1996) and Anmyeon Bridge (1997)
As mentioned above, the collapse of Sungsu Bridge happened in 1994. This accident emphasized the significance and necessity of maintenance system for bridges to prevent both human and economical losses. Accordingly, in 1995, the governmental authorities issued more stringent requirements on bridge management and operational programs including systematic visual inspection, instrumentation, load capacity tests and field measurements. This started structural health monitoring of bridges in Korea with stand-alone field system consisting of sensors, field hardware and online signal transmission. Such stand-alone systems were installed on existing bridges like Namhae and Jindo bridges in order to collect field data by full scale load capacity test and evaluate their structural health [2,3,5,6].
2.3 Third Generation of Sea-Crossing Bridges in Korea (2000-2004)
The first years of the 21st century marked milestones in the development of sea-crossing bridges in Korea. Differently from the second generation where economy and functionality were governing critically the design, the third generation of sea-crossing bridges focused on aesthetics considering the potential tourism resources offered by bridge structures. Significant achievements were thus realized through the construction of remarkable cable-supported bridges along the coastal areas. This allowed domestic bridge engineers to establish self-reliant technology for special bridges like cable-stayed and trussed arch bridges. Table 1 gives a list of the sea-crossing bridges of the third generation and Fig. 6 illustrates major bridges built during that period.
Fig. 6 Views of Seohae Bridge, Youngjong Bridge and Gwangan Bridge T a ble 1 Third generation of sea-crossing bridges in Korea
Youngjong Bridge, completed in 2000, is part of the Incheon International Airport Highway connecting Seoul and Incheon International Airport. Being the first bridge foreign visitors meet when arriving in Korea, special attention has been paid on its design with unique and pioneering features such as three-dimensionally profiled suspension cables and selfanchoring. The double decks are Warren truss with 6 roadway lanes at the upper deck and 4 roadway and 2 train lanes at the lower deck [2,7,8,9].
Bridge name
- Year
- Characteristics (unit: m)
- Bridge type
- Length Mainspan
- Seohae
- 2000 Composite cable-stayed
2000 Self-anchored suspension 2000 Balanced arch truss 2001 Steel cable-stayed 2002 PSC box girder 2202 Earth-anchored suspension 2003 Rose arch 2003 Steel arch
7,310 4,420 2,559 1,250
340
7,420
340 317 436 760 840 182
470 300 540 240 160 500 180 220 230 160 160 182
Youngjong Banghwa Youngheung Neukdo Gwangan Danhyang Choyang Samcheonpo Gogeum
2003 Composite cable-stayed 2003 Steel arch
Wando-Shinji 2004 Steel plate box Shinjeodo 2004 Nielsen arch
Most of the bridges of the third generation are equipped with modern monitoring systems from sensing to processing. A special feature is the integration of the health monitoring systems of Youngjong Bridge Seohae Bridge, currently the longest cable-stayed bridge in Korea, and Banghwa Bridge, the 27th bridge crossing Han River in Seoul, in order to reduce costs and improve the efficiency of management [2,10]. The data collected at each bridge are processed exclusively at each field station for real-time monitoring and detection of anomalies. But data useful for long-term evaluation of bridge condition and periodical inspection data are transmitted through high-speed internet line to a unique management center remote from the sites [3,4].
3. Current Bridge Construction Activities in Korea
The outstanding and rapid evolution of bridge technology in Korea has been observed throughout three periods of sea-crossing bridges that are technology introduction, imitation and self-reliance periods. Advances have been realized in all fields from design to construction with gradual independency from foreign technologies. As a result, Korea can now be counted among the leading group in bridge engineering. Especially in the domain of structural health monitoring, the systems installed in the bridges of the third generation have become benchmarks for most of the cablesupported bridges built worldwide.
T a ble 2 Recent bridge constructions in Korea
- Current
- bridge
- construction
activities can be classified as the fourth generation of bridges in Korea. Focus is done on diversification and aesthetics due to changes in tendering policy which is shifting into turnkey and proposal. Tendency is also to apply more rationally the current design codes through mixed application of Korean and foreign
Bridge name
Year Characteristics (unit: m)
- Bridge type
- Length Mainspan
Second Jindo 2005 Cable-stayed Machang Sorok Keumbit Shinwando Geumga Incheon Goha-Jookgyo 2009 Steel-cable-stayed Dolsan-Hwatae 2009 Composite cable-stayed Jeokgeum
484
1,700
344
- 400
- 2008 Steel composite cable-stayed
2008 Mono-cable self-anchored suspension 1,160 2009 5-span bundle type cable-stayed 2009 Steel cable-stayed 2009 Continuous 7-span extradosed 2009 Steel box girder cable-stayed
250
2,028
430
480 200
1,660 1,480 3,060 1,435 1,340 8,200
5@125
800 500 500 850 475
- design
- specifications.
- After
successful achievements of cablestayed bridge using domestic technology, the Korean bridge engineering community has also established self-reliant technology for suspension bridges. Table 2 gives a list of recent bridge constructions in Korea of which several examples are reviewed with their special features.
2009 Earth-anchored suspension
Busan-Geoje 2010 2-pylon cable-stayed
- 3-pylon cable-stayed
- 2@230
3,240
155 540
4@160
840
Immersed tunnel
- 2010 Extradosed
- Woonnam
Bukhang Muyoung Mokpo Gwangyang Ulsan
925
1,114
860
3,240 2,260 2,970
2011 Steel composite cable-stayed 2011 Continuous 5-pylon cable-stayed 2011 Suspension 2012 3-span suspension bridge 2014 Suspension
1,545 1,150
3.1 Incheon Bridge
Incheon Bridge (Fig. 7), currently under final construction stage, is a steel box girder cable-stayed bridge, which will link Incheon International Airport with Songdo New Town in the southern part of Incheon city. The total bridge length will be approximately 12.3km, including the cable-stayed bridge, approach bridges and viaducts, and will carry six lanes of traffic across the straits between Youngjong Island and the mainland. The cable-stayed bridge is a 1,480 m long structure with main span of 800m that will make it the world’s fifth longest cable-stayed bridge at completion. The inverted pylons of the cable-stayed bridge are supported on drilled shaft piling foundations and rise up 238m high. The Y-shaped pylons are reinforced concrete hollow section in a diamond configuration which provides torsional stability to the main span and minimizes the size of foundation. Two planes of PPWS stay cables support a 33.4 m wide streamlined orthotropic steel box girder. The pilecaps of the pylons were constructed above high tide level in precast concrete permanent formwork housings so as to allow for easy and economical construction in the marine environment [11].
Fig. 7 Overview of Incheon Bridge
The majority of the length of the bridge is constructed as low level viaduct structures with pretensioned precast 50m long concrete box girder spans. Where the alignment rises to cross the navigation channel, precast segmental balanced cantilever approach bridges with 145m spans link the viaducts to the cable-stayed bridge. The continuous aerodynamically shaped five-span steel box girders have a clearance of 74m above sea level for ship passage to the Port of Incheon. Ship collision protection is provided in the form of sacrificial dolphin structures which are configured around the piers close to the navigation channel. The design included impact analysis and assessment of the plastic deformations that withstand the impact energy from a 100,000DWT ship hitting a sheet pile cell head-on at high speed [12].
The bridge is constructed over tidal flats and up to 20m depth of water. Marine deposits overly rock stratum. All of the foundations are large diameter cast-in-place concrete piles disposed in the weathered or soft rock stratum. Korea being located in a region of moderate seismicity, the bridge is designed for a 1,000-year return period event, which governs the design of the substructures. In addition, the bridge can be subject to typhoon wind loading, which is significant for the high level structures. In particular, wind buffeting loads and aerodynamic stability have been important factors in the design of the cable-stayed bridge.
The project is being procured by the Korea Expressway Corporation on a BOT (Build Operate Transfer) basis. As a fast track project, the design was prepared as a sequence of packages in accordance with the demands of the construction schedule.
3.2 Busan-Geoje Fixed Link
The construction of Busan-Geoje fixed link, a motorway between the city of Busan and the island of Geoje, started in 2004 and is expected to be completed in December, 2010. This project will provide an 8.2km-long four-lane fixed link of which 3.7km of undersea tunnel and 2km of cablestayed bridges to replace the current route of 140km needing ferry travel. The immersed tunnel located in a strong seismic area will rank among the longest in the world to date and will be the deepest road tunnel ever constructed at a maximum water depth of 50m (Fig. 8). The choice for undersea tunnel was governed by the request of the Navy for structures minimizing at the most the obstruction of the main navigation channel. The tunnel is made of 18 precast tunnel elements of 50,000t that are floated into position and sunk into a pre-dredged trench. Securing water-tightness of the joints, preparing the tunnel supports and placing the sections are thus technological challenges to be faced during construction [13].
Fig. 8 Mooring of precast tunnel elements and drainage of immersed tunnel element chamber
The site being directly exposed to the South Sea, the design of the cable-stayed bridges has to accommodate harsh environmental conditions like typhoons and high tides. The first bridge is a three-pylon cable-stayed bridge with two main spans of 230m and the second bridge is a two-pylon cable-stayed bridge with main span of 475m for total lengths of 2,363.5m and 1,856m, respectively (Fig. 9). Both cable-stayed bridges are founded on caissons fully prefabricated offsite and transported to the site. The concrete pylons are designed with slightly inward curving legs. The curvature of the legs is limited by a “no tension” criteria for dead load and the use of standard climbing form equipment. The bridge deck is a traditional steel-concrete composite girder. The approach bridges are composite girder arranged with 90m spans. All elements of the approaches are prefabricated offsite in three elements, caisson, pier shaft and deck and will be transported on site using a 3000t floating crane. AASHTO LRFD (Load and Resistance Factor Design) is applied as design codes [14]. The project is being implemented along the lines of the privately financed BOT model and executed through Fast Track together with PMIS (Project Management Information System).
