The Tseung Kwan O Cross Bay Link Bridge, which was completed and opened to traffic in December 2022, has the largest span and heaviest prefabricated steel arch bridge in Hong Kong. Mr. Wang Yanhua, Chairman of China Road and Bridge Corporation (Hong Kong), recently stated in a media interview with Ta Kung Pao and Wen Wei Po that if traditional offshore construction methods are difficult to carry out, then there will be "innovation" in construction methods, materials, and installation methods. He shared that the main arch bridge, which weighs over 12000 tons and is 214 meters long, could not be lifted and installed by any existing crane. In the end, the arch bridge was accurately installed onto the bridge piers using the force of natural tides, which was also the first time in Hong Kong to use the "float-over method" to build a bridge. The total weight and installation time of the floating-over broke the overall installation record for a single arch bridge.

Mr. Wang Yanhua said that this offshore project is located in the east of Hong Kong, which has been greatly affected by typhoons in the past. If traditional offshore operations are used, many temporary supports need to be built. In case of typhoons, it is difficult to ensure site safety. After careful consideration, in order to ensure high-quality delivery of the project on schedule, improve site safety, and minimize the impact of construction on the surrounding residents, we have decided to use modular construction technology on a large scale to reduce on-site work.

At the beginning of the construction of the bridge, the "2019 Turmoil" happened, followed by the global COVID-19. It was difficult to move people, but the project could not be stopped. Due to the large number of bridge components being produced and assembled at the Nantong factory in Jiangsu Province, construction management personnel in Hong Kong need to be present to supervise the construction process and ensure the quality of works.

He mentioned that during the peak of the epidemic, his Hong Kong colleagues in Nantong had their original hotel requisitioned as a quarantine hotel. In order to facilitate their work, they overcame the inconvenience of living conditions and moved to the workers' dormitory in the factory, ultimately completing their work excellently. The head of the Project Planning Department was a colleague sent from Mainland China to Hong Kong and did not return home to Beijing for 21 months during the epidemic.

New type of steel material reduces the weight of bridge by 30%

We put aside our yearning for our families, and faced the risk of infection of COVID-19, we also had to bear the heavy pressure during the fabrication of large steel components. Mr. Wang Yanhua said that there are more than 20 intermediate loading cases in the manufacturing, transportation and installation of the bridge. The most difficult thing is the geometry control of the bridge. If actual force deviates from the calculated force, all previous efforts will be wasted. Therefore, at some critical times, everyone needs to work 24 hours a day.

Persisting in innovation requires going through countless trials and tribulations. The adoption of innovation started from the use of new steel materials. Wang Yanhua said that this is the first time in the world that S690 high strength steel is used in bridge construction. The use of new steel materials can reduce the weight by 30% and carbon emissions by 25% compared with traditional steel, but the higher the strength, the greater the brittleness. The question arises, how to carry out a large-scale welding of new materials for a double arch structure with a total weight of over 12000 tons?

Collaborate with PolyU to research the best welding parameters for over six months

Mr. Wang Yanhua introduced that the National Steel Structure Engineering Technology Research Center Hong Kong Branch of Hong Kong Polytechnic University has conducted research with the CRBC for more than half a year, and finally obtained the optimal welding parameters, which have been successfully applied to the fabrication of the main arch bridge structure, achieving a new technological breakthrough in the steel structure industry in Hong Kong.

After confirming the welding technology, the main arch bridge was prefabricated and assembled at the Nantong factory, and the bridge as a whole was loaded out to the delivery barge. In the 2021 Spring Festival, the main arch bridge departed from the factory in Nantong by a semi-submersible barge, and after voyage of 8 days and 8 nights, nearly 1700 kilometers of sea transportation, finally arrived at Tseung Kwan O Bay, but the sea was not calm.

Mr. Wang Yanhua recalled that during transportation, it happened to be in winter. Due to the monsoon, the waves in the entire Taiwan Strait were very strong, with waves up to five or six meters high. However, the transportation time cannot be delayed, and the window period for installing the main arch bridge using tides must be accurately grasped. In order to ensure the safe and timely arrival of the main arch bridge at Hong Kong, a large number of contingency plans need to be made in the early stage, such as how to handle strong winds and waves, finding temporary shelters, etc.

Finally, it was the critical moment to use the "float-over method". At around 7am on February 26, 2021, the semi-submersible barge moved between the bridge piers while grasping the high-water level. After aligning with the position of the double arch steel bridge, the semi-submersible barge gradually pumped 27000 cubic meters of seawater for ballasting, and the hull of barge gradually sank about one meter, allowing the double arch steel bridge to sit on the pier and complete the installation of the main arch bridge in one go. This is also the first time in Hong Kong that the "float-over method" has been used to build a bridge.

Developing intelligent robots to promote the transformation of the Hong Kong construction industry

New infrastructure projects in highly urbanized areas like Hong Kong often face challenges such as limited space, heavy traffic, and strict environmental requirements. Mr. Wang Yanhua, chairman of CRBC Hong Kong, said that taking the Lok Ma Chau Loop Development project as an example, it showed how technology can solve these problems. "The traditional bridge construction often needs to close the road, which has a great impact on the traffic." He said that CRBC independently developed the technology of " full-span deck erection technology for land viaduct" and "360° Rotating Special Lifting Frame (SLF)", which successfully achieved the lifting of whole span in one go, reduced the interference to existing traffic, and improved the construction efficiency and safety. This innovation not only won the Outstanding Environmental Management, Safety Innovation, and Considerate Contractor Site Award for the project, but also provided a replicable solution for similar projects in Hong Kong.

For the construction industry in Hong Kong, there has been a long-term shortage of skilled workers and high risks associated with working at height and confined space operations. CRBC (Hong Kong) has targeted these pain points, increased research and development investment, and launched a series of intelligent construction equipment. Mr. Wang Yanhua said, "We have developed an intelligent Remote-controlled Self-propelled Piling Platform and pipeline welding robot, which not only reduces the dependence on manpower, but also greatly improves construction accuracy and safety." The application of these technologies marks the transformation of Hong Kong's construction industry from traditional labor-intensive to "intelligent and automated", forming new quality productivity.

In addition, the environmental issues of Tseung Kwan O-Lam Tin Tunnel Road P2 and Associated Works have attracted much attention. Mr. Wang Yanhua introduced that CRBC innovatively adopts the "double water gates" technology to completely block the flow of muddy water into public waters. He stated that this technology not only protects the marine ecology, but also brings new environmental protection measures for Hong Kong's future reclamation projects.