Front. Archit. Civ. Eng. China 2011, 5(4): 405–414 DOI 10.1007/s11709-011-0136-4

REVIEW

Michael CH HUI, Doris YAU Major development in , China—past, present and future

© Higher Education Press and Springer-Verlag Berlin Heidelberg 2011

Abstract The first “modern” type of vehicular bridge (the then British Foreign Secretary) had disparagingly was built in Hong Kong China in the 1920s. The need for described as “a barren island, with hardly a house upon it”. an efficient transportation system to cope with population Subsequently, Hong Kong started to develop into an growth and enable economic development has demanded industrial and manufacturing center after the Second World the construction of more and more since the middle War. Transportation networks were also developed to cope of the 20th century. By 2007, Hong Kong had a total of with ever-increasing economic and social activities. More about 1300 vehicular bridges. Four of these bridges, and more bridges have since been built. To transform Hong including the , Bridge, Kong from an industrial city to an international financial Bridge, and the cable-stayed bridge on the Hong center in the late 1990s, Hong Kong was in need of a Kong- Shenzhen Western Corridor, are considered to be world-class international airport and an efficient transpor- major bridges supported by cables. Currently, the Stone- tation network to connect the airport with the various parts cutters Bridge on Route No. 8 is under construction and is of the city. A number of major cable supported bridges expected to be completed in late 2009. At the same time, were built on the airport access routes as a result. the Hong Kong-Zhuhai-Macao Bridge will be in its Upon completion of the airport project, the focus of road detailed design stage soon. While efforts have been made transport projects was transferred to cross boundary by bridge builders to construct these giant structures, the crossings and the improvement of the local strategic road upkeeping of these valuable assets at a high standard and network. The Hong Kong-Shenzhen Western Corridor ensuring their continuous functioning and performance (HK-SWC) was completed 10 years after the territory’s during their intended lifespans will be another important return to the Mainland. Meanwhile, the Stonecutters task for bridge engineers. Wind and structural health Bridge on Route No. 8 is currently under construction monitoring system (WASHMS) will play a key role in this and is expected to be completed in late 2009. respect. Looking to the near future, the mega Hong Kong- Zhuhai-Macao Bridge will soon enter its detailed design Keywords Tsing Ma Bridge, , Ting phase for target commencement in 2010. Experience Kau Bridge, , Hong Kong-Zhuhai- gained in constructing the earlier major bridges will Macao Bridge, wind and structural health monitoring definitely contribute to building this mega bridge. system (WASHMS) 2 Bridge building in Hong Kong 1 Introduction 2.1 Early days Looking back in history, Hong Kong, China began in the middle of the 19th century as a fishing village where one Hong Kong has a steep and hilly terrain. In the old days, could hardly find any bridges on what Lord Palmerston most of its inhabitants could only cluster along the northern shore of and on the Received September 2, 2011; accepted September 28, 2011 Peninsula. Throughout the 19th century, sea transport was ✉ the only means of . All movement Michael CH HUI ( ), Doris YAU of goods within or outside the territory had to be done by S15/F, Civil Engineering and Development Building, 101, Princess Margaret Road, Ho Man Tin, Kowloon, Hong Kong, China sea as all warehouses lay along a 5 km stretch of the E-mail: [email protected] Island’s northern shore. The first motor car was delivered 406 Front. Archit. Civ. Eng. China 2011, 5(4): 405–414 to Hong Kong in 1915, but it was not until the 1920s that service-based economy in the 1980s and then matured to steps were taken to cater for motor vehicles specifically. become a financial center in the 1990s. This was the time when the first “modern” vehicular bridge From the 1980s to the late 1990s, Hong Kong was at its (Kwong Fuk Bridge) in Tai Po was built (Fig. 1) [1]. Even golden age of bridge building during which a number of in the immediate post-Second-World-War years, Hong world class bridges were built. In the late 1980s/early Kong had very few local industrial and economic 1990s, Hong Kong decided to move its airport from the activities. Apart from railway, the most common types of city center of Kowloon to on the Lantau land transport at that time were rickshaws and sedan chairs. Island. The new airport necessitated the construction of a Bridges were usually built using primitive materials like major new strategic highway of approximately 34 km in timber, stone, or cast iron. length between the western part of Hong Kong Island and The situation changed in the 1960s when Hong Kong the airport. This was the first physical connection between experienced a sudden surge in population growth due to the Kowloon Peninsula and Lantau. The key part of the the influx of immigrants from the Mainland. As industry connection is the spectacular 4 km long , developed and population began to multiply, Hong Kong comprising the 1377 m span Tsing Ma suspension bridge was faced with the urgent task of providing homes and and the 430 m span Kap Shui Mun cable-stayed bridge. infrastructures for its people. An ambitious program was These two bridges carry both road and rail traffic. implemented to provide new homes in the new towns of Shortly after the commissioning of the Airport Access the for about 1.8 million people in mid Links, the Route No. 3 (Country Park Section) was 1980s. One of the foremost items in this program was to commissioned in 1998 to connect traffic from the north- provide better transport connections among these new west New Territories to the Lantau Link. The 1177 m long towns. As a result, more and more bridges and viaducts Ting Kau cable-stayed bridge forms part of this route. It is were constructed as part of the program. With such a boom a unique and visually impressive structure, which in the bridge construction industry and advances in continues to attract world-wide and local interest. construction technology and material science, bridges The was an extremely complex were usually designed as reinforced/prestressed concrete and fast tracked program. To ensure successful implemen- structures. Moreover, the precast segmental construction tation of this ambitious program, Hong Kong looked for method was introduced to Hong Kong in the 1980s for imported technology including different levels of expatri- constructing bridge viaducts over busy roads or above the ate personnel from experts down to construction super- sea near the shoreline. visors and skilled laborers. As a result of the technology transfer, Hong Kong has nurtured a number of experts in bridge construction and project management. The quality and standard of the local construction industry have also been improved significantly. The following major bridges were constructed during the golden age of bridge building history in Hong Kong.

2.2.1 Tsing Ma Bridge [2]

Tsing Ma Bridge has a main span of 1377 m and an overall length of 2160 m (Fig. 2). Obviously, a bridge of this span length would be extremely flexible and wind sensitive. The following discussions will focus on this aspect. As the Tsing Ma Bridge will be the only road/rail link to the airport, it is essential that this access be maintained in all but the most severe weather conditions. This “all-weather” capability is achieved by locating the Fig. 1 Kwong Fuk Bridge in Tai Po two railway tracks and two protected roadways in the lower deck, where they will be protected by stainless steel 2.2 Hong Kong’s new airport cladding. The final design uses a double-deck steel box construction with truss stiffening and non-structural edge China started to implement its open-door policy in the late fairings (Fig. 3). 1970s. As a result, industrial activities in Hong Kong were Learning from the experience of the Tacoma Narrows gradually shifted northwards to areas in the Bridge collapse in 1940, the deck of the Tsing Ma Bridge Delta such as . Hong Kong underwent a rapid was streamlined. Extensive wind tunnel tests confirmed transition from an industrial and manufacturing center to a that the adoption of a streamlined deck section with faired Michael CH HUI et al. Major bridge development in Hong Kong, China—past, present and future 407

Fig. 2 Elevation of the Tsing Ma Bridge

2.2.2 Kap Shui Mun Bridge [2]

The Kap Shui Mun Bridge has a main span of 430 m and an overall length of 750 m (Fig. 4). Like the Tsing Ma Bridge, it carries a six-lane highway on the upper deck and twin railway tracks plus two sheltered road lanes on the lower. It is supported by two planes of stay cables. The bridge is a record-breaker in its own right, but is often overshadowed by its giant neighbor on the same link. There are a number of unique features on this bridge. It is one of the stiffest structures ever to be incrementally launched, and has perhaps the most heavily-loaded cable stay towers ever built. The middle 387 m of the 430 m Fig. 3 Hybrid arrangement of stiffening truss and box of the central span is a steel/concrete double-composite box Tsing Ma Bridge section (Fig. 5). The upper and lower concrete decks are cast onto the prefabricated steel webs at the Lantau side edges and central air vent would ensure aerodynamic of the site, before being floated out and hoisted into stability in an extreme wind speed of 95 m/s (one-minute position. The side span and the transition elements of the mean). In addition, investigations were undertaken to central span are of post-tensioned in situ concrete. The ensure that the air flow within the lower deck would be at transition elements are jacked into position, through the low speeds, as required for highway and railway operation. middle of the towers, by the incremental launching It has been established by wind tunnel measurements that method. This method was used for the first 45 m of the the wind speed in the sheltered deck will be approximately central span coming out from each of the towers, i.e. up to 40% of the external wind speed. Graduated wind shields adefining point where water in the Kap Shui Mun Channel are provided on the upper deck adjacent to the bridge would be deep enough to allow the composite units to be towers. floated out.

Fig. 4 Elevation of the Kap Shui Mun Bridge 408 Front. Archit. Civ. Eng. China 2011, 5(4): 405–414

is stabilized by a pair of longitudinal stay cables connecting the tower head to the deck sections adjacent to the side towers. According to the bridge designer, the special design of the bridge towers was somewhat analogous to “working and appearing like masts of sailboats”. They may make the road users feel like “entering a ship crossing the and then leaving it again.” The two separated bridge decks supported by four planes of cables on both sides of the three towers Fig. 5 Steel/concrete double-composite box section of the Kap contribute to the slender appearance of the bridge, and Shui Mun Bridge are considered to be aerodynamically favorable. Owing to a short design and construction period, a composite 2.2.3 structure was adopted for the deck design. The steel/ concrete deck comprises a steel grid of two main outer The Ting Kau Bridge has an overall length of 1177 m girders with steel cross girders spanning 18.77 m at with two cable-stayed spans measuring 475 and 448 m 4.5 m spacing and a concrete slab on top formed by  (Fig. 6). One of the outstanding features of this “landmark 4.4 m 4.6 m precast panels of 230 mm thick and cast in bridge” is the three towers, with heights of 172, 200, and situ joints (Fig. 7). 163 m above the Hong Kong Principal Datum, located on the Ting Kau Headland, on the reclaimed land, and on the 2.3 Post-1997 north-west shoreline, respectively. In addition to transverse stabilization cables, the 200 m tall central tower In 2001, with increasing economic and social activities

Fig. 6 Elevation of the Ting Kau Bridge

Fig. 7 Erection of the deck of Ting Kau Bridge Michael CH HUI et al. Major bridge development in Hong Kong, China—past, present and future 409

Fig. 8 Elevation of the Shenzhen Western Corridor Bridge between Hong Kong and the Mainland, the three existing 3 Present Hong Kong-Shenzhen vehicular border crossings became nearly saturated. The governments on both sides recog- The design and construction of the 1018 m span Stone- nized the need to construct the fourth crossing to alleviate cutters Bridge represent the present situation of major the traffic congestion at the existing border crossings and to bridge development in Hong Kong. The bridge is a key facilitate the flow of people and cargo between the two element on Route No. 8 leading to the airport in Hong places. It was decided to place the fourth crossing to link Kong. The route is being built to relieve traffic congestion up the North-west New Territories with Shekou of on the existing airport access Route No. 3 and is expected Shenzhen across the Deep Bay, i.e. the Shenzhen Western to be completed in late 2009. Corridor (HK-SWC). Hong Kong presents a unique maritime setting that Deep Bay has a high ecological value because of its makes it one of the world’s remarkable places. The extensive low-lying inter-tidal mudflats and mangrove Stonecutters Bridge will be a major landmark in the forests. The alignment of the corridor was chosen carefully western area of the harbor and will be visible from many through the cooperation of governments on both sides of parts of Hong Kong. Hence, the the border. The Hong Kong section of the HK-SWC was determined to deliver this mega bridge project at the includes the construction of a cable-stayed bridge with a highest aesthetic standards and raise it to an iconic status 159 m tall single concrete inclined tower and a 210 m long with symbolic value. The following is a brief account of steel main span supported by a single plane of cables what have been done with a view to achieving this goal. (Fig. 8). The deck is a single steel box girder 38 m wide and 4 m deep (Fig. 9). 3.1 International design competition

For the first time in Hong Kong, the conceptual design of the bridge was obtained through the conduct of an open international design competition. The main objective of the competition was to secure a reference scheme that would make the Stonecutters Bridge stand out among the world’s long span bridges and become a fitting landmark of the harbor and a gateway for the container terminal, thereby underlining and promoting the image of Hong Kong as a vibrant and important center of international trade. The competition was conducted in two stages, with 27 entries in Stage 1 which were whittled down to 5 in Stage 2. The entries were assessed by two committees, i.e. the Technical Evaluation Committee and Aesthetic Evaluation Committee, each of which comprised interna- tional and local experts as judges. The winning design was Fig. 9 Erection of the 38 m wide and 4 m deep steel box girder a cable-stayed bridge with two mono-column pylons each 410 Front. Archit. Civ. Eng. China 2011, 5(4): 405–414

298 m high and an aerodynamic twin deck. The total length 3.2 Aerodynamic considerations of the bridge is 1596 m with a main span of 1018 m. It has four back spans having lengths of 79.75, 70, 70 and 69.25 For a twin deck structure like the Stonecutters Bridge, m at each side of the main span, respectively. The towers vortex shedding actions may be amplified as the shed are in concrete up to level + 175 m and in steel-concrete vortices drift across the central air gap and impinge on the composite from level + 175 m to level + 293 m with the downwind girder. One effective way to mitigate vortex outer skin being stainless steel. The top 5 m are a glass induced oscillation is to provide guide vanes at the flow covered steel structure, which acts as an architectural separation point (at the knuckle line) of the soffit in order to lighting feature and provides storage space for main- guide the air flowing underneath the deck to prevent or tenance equipment. The bridge deck at the central span and diminish rhythmic vortices formed at the upwind knuckle in the vicinity of towers will be of steel while the side spans line of the windward deck [3]. This method has will be of concrete. The twin longitudinal deck girders are successfully been adopted in mitigating the vortex induced 14.3 m apart and are connected by cross girders at 18 m oscillation of the Storebaelt Bridge. Figure 12 illustrates and 10 m intervals in the central span and side spans, the concept. Like many other projects, the study of vortex respectively. The two planes of stay cables take a modified shedding vibration of the Stonecutters Bridge deck fan arrangement, anchored at the outer edges of the deck employed sectional models of a scale of 1∶80. The test also at 18 m spacing in the central span and 10 m spacing in results indicated that the guide vanes had not been effective the back spans. Please refer Figs. 10 and 11 for the general in mitigating vortex shedding vibration. It was thought that arrangement of the bridge. with the low Reynolds no. (Re) employed in the 1∶80 scale

Fig. 10 Elevation of the Stonecutters Bridge

Fig. 11 Steel deck section of the Stonecutters Bridge Michael CH HUI et al. Major bridge development in Hong Kong, China—past, present and future 411

stainless steel reinforcement for the outermost layer and the ties. 2) The use of duplex grade stainless steel for the steel/ concrete composite upper tower structure. 3) The use of a dehumidification system for the inside of steel deck to avoid the use of a sophisticated painting system, which would be costly to apply and maintain.

3.4 Maintenance considerations [6] Fig. 12 Anticipated flow pattern without and with guide vanes 3.4.1 Maintenance access wind tunnel test, the boundary layer growing along the soffit plate becomes rather thick, thus limiting a high flow It is a basic principle in the design that all important parts rate through the vanes, making the vanes ineffective [4]. of the structure should be accessible. Access facilities Hence, it was decided to pioneer some high Re tests in therefore are designed to meet this principle. Access to all order to further investigate the effectiveness of the guide important parts of the structure must be achieved without fi vanes. Sectional model tests using a bigger scale of 1∶20 any disruption to traf c, which given the strategic nature of were then carried out in a bigger wind tunnel with higher the Stonecutters Bridge as a major route to the Hong Kong wind speeds with a view to raising Re by one order of airport and container terminals, is a major consideration. magnitude. The guide vanes design which had failed in the Apart from the routine maintenance access provided in the 1∶80 scale tests proved to be very efficient in the 1∶20 scale earlier major bridges such as the rack and pinion lift for tests. The vortex shedding vibration response was maintenance inside the bridge towers and the underslung completely eliminated. A number of interesting findings gantries for maintenance outside the steel deck and stay were also revealed in determining the steady-state aero- anchorages, the Stonecutters Bridge will also be equipped dynamic force coefficients under different Re [5]. with a shuttle train running along the entire length of the deck for personnel and equipment (Fig. 13). The exterior 3.3 Durability considerations [6] of the towers above deck level is accessible from a cradle suspended by a permanent derrick on the tower top. While great efforts have been made to obtain a high standard and quality design through the conduct of an 3.4.2 Wind and structural health monitoring system international design competition, it is equally important to (WASHMS) ensure that the bridge will be durable and that the special features built into the design can be long lasting with Bridge health monitoring serves an important role in minimum maintenance effort. The conduct of a proper predicting the structural behavior of long span bridges and durability assessment of the design will provide the helping bridge owners to maintain their valuable assets. necessary framework for achieving that goal. Some special The Highways Department has ten years of experience in measures have been adopted in the Stonecutters Bridge operating a sophisticated wind and structural health project from a durability point of view, such as: monitoring system for long span cable-supported bridges. 1) The use of micro-silica to make the concrete of lower WASHMS was first installed on the Tsing Ma Bridge, the tower less permeable, coupled with the use of Grade 304 Kap Shui Mun Bridge and the Ting Kau Bridge in 1997.

Fig. 13 Shuttle train inside the southern girder of the Stonecutters Bridge 412 Front. Archit. Civ. Eng. China 2011, 5(4): 405–414

With the experience gained in operating this system for a 4 Future few years, the second generation was evolved and put into practice on the cable-stayed bridge in HK-SWC. Again, The implementation of the new airport and its access route with the experience gained in implementing the HK-SWC 10 years ago is a milestone in Hong Kong’s major bridge WASHMS, the Highways Department has designed the construction history. At the same time, the transportation third generation WASHMS, which is being installed on the network of Hong Kong started to take shape. The Stonecutters Bridge (Fig. 14). The third generation system completion of HK-SWC in 2007 and the full commission- addresses the problem encountered in the earlier systems ing of Route No. 8 including the Stonecutters Bridge where data retrieval from storage for processing and by end of this year will refine the network. To further analysis was inefficient. The system also enhances the enhance Hong Kong as a transportation hub, there are a correlation and regression analyses to be carried out in number of mega scale road and railway routes being different views varying from two-dimensional to multi- planned for completion by the middle of the next decade. dimensional views thus making the structural health The majority of these projects, however, are tunnels. As monitoring system more user-friendly [7]. far as bridges are concerned, the focus will be placed on the Hong Kong-Zhuhai-Macao (HKZM) Bridge and its 3.5 Summary link road to the existing transportation network. The HKZM Bridge comprises a proposed series of bridges The planning, design and construction of the Stonecutters and tunnels that would connect the west side of Hong Bridge posed many challenges to bridge engineers. The Kong with Macao and the neighboring city of Zhuhai high quality expectations in a landmark structure justifies which is situated on the west side of the Pearl River Delta the conduct of an international design competition to (Fig. 15). The proposed 29 km bridge is comparable obtain an elegant design. After that is achieved, the next with the world’s longest bridge, the Second Lake important mission is to ensure that such a design will be Pontchartrain Causeway in the United States, which is buildable, durable, easy to maintain, and safe to operate. 38.4 km long. Construction is expected to commence in Much effort has been spent in various stages of the project late 2009 but no later than 2010. The bridge will be to achieve these goals. With its construction commenced in completed around 2016. April 2004, the Stonecutters Bridge is now at the most Looking to the farther future, we have devised critical stage of its life where all the planned and designed preliminary conceptual plans to build more strategic routes measures will be implemented to ensure the health of the to link up with the West New Territories. bridge when it is born in 2009. These preliminary plans may opt for long span bridge

Fig. 14 Wind and structural health monitoring system of the Stonecutters Bridge Michael CH HUI et al. Major bridge development in Hong Kong, China—past, present and future 413

Fig. 15 The Hong Kong-Zhuhai-Macao Bridge solutions. However, it might be too early at this stage to condition-based maintenance. There are therefore still a lot even make a prediction on what will happen. of potential for further research and development in To ensure that Hong Kong will continue to enjoy a WASHMS. sustainable development in the years to come, one important aspect is to upkeep our valuable assets to a high standard. WASHMS will play a key role in this 5 Conclusions exercise. WASHMS in Hong Kong was born ten years ago. The systems as well as their master bridges therefore are Bridge construction is critical to the development of still at their young ages. Up to this point, major structural Hong Kong and its economy. Bridges narrow the gaps defects still have not been observed. We will take this between one region and another throughout the opportunity to plan and schedule the work of WASHMS territory. Bridges speed up cross-region and cross-border such that we could prepare ourselves for the near future movement of people and goods and improve the overall before our valuable stock of elegant bridges gets older and efficiency of the transport system. During the past years, suffers from health problems. While they are young and bridges were built because of better economic conditions strong, we can carry out investigation work on the and more bridges also bring about better economy to Hong structural performance of the bridges and set up computer Kong. bridge models to predict/evaluate the bridge responses The bridge construction techniques in Hong Kong during in-service (mainly for fatigue assessment) and became mature with the completion of several large-scale extreme events (mainly for stability and damage assess- bridges over the years. Like many other developed ments). Such investigation and development work will countries, the focus of bridge engineering will unavoidably provide valuable information and solutions to the bridge be shifted to the maintenance and operation of the “ ” operators as the bridges get older and weaker . As time completed bridges. WASHMS plays a key role in this goes by, the number of damaged or deteriorated compo- respect. nents in old bridges due to degradation will increase. The understanding of the deterioration process will not Acknowledgments The authors wish to express their gratitude to the only improve the efficiency of the corrective/preventive Director of Highways of HKSAR, C S Wai, for his permission to publish this maintenance, but also provide solutions for predictive/ paper. Views expressed in the paper are entirely those of the authors. 414 Front. Archit. Civ. Eng. China 2011, 5(4): 405–414

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