The greatly anticipated Tseung Kwan O Cross Bay Link (TKO CBL) will be commissioned on 11 December 2022. Upon commissioning, it will provide a dual two-lane carriageway, a cycle track and a footway, becoming the first 3-in-1 marine viaduct in Hong Kong. Previously, Ir Thomas HO, Chairman of the Construction Industry Council, visited the bridge to understand the innovative technologies and industrial breakthroughs adopted in this project. According to the project team, extensive prefabrication and Design for Manufacture and Assembly (DfMA) is widely adopted, which helps enhance speed, safety and quality.
The First Project To Extensively Use S690QL High-strength Steel
The 1.8km-long TKO CBL connects Wan Po Road from LOHAS Park or TKO Industrial Estate to the TKO – Lam Tin Tunnel which will also be commissioned on the same day. The CBL contains 1km-long marine viaduct, which appears as a symbol of ‘∞’, demonstrating the theme of Eternity Arch. It is also China’s first marine arch bridge project using S690QL high-strength steel extensively. Its great tensile strength enable the bridge to use less material under the same loading condition, thus contributing to sustainability and enhancing it aesthetically.
Extensive Prefabrication And DfMA Plays A Crucial Part
The TKO CBL Main Bridge Contract commenced in July 2018. Design for Manufacture and Assembly (DfMA) was adopted at early stage with extensive prefabrication. One prominent example is that while the bridge foundation was being constructed at Junk Bay, bridge components of the marine viaduct were being fabricated at off-site yards in the Mainland concurrently. As offsite yards provided a controlled environment, quality of the components is enhanced and hence speeding up the progress. Mr. Anson SIT, engineer of the Civil Engineering and Development Department, also said that extensive prefabrication and DfMA could minimize disturbance to the community, reduce construction time and risk of working at height, above waters.
The highest point of the bridge arch is 70m metres above sea level and the main span is 200 metres long. To provide sufficient space for vehicles, pedestrians and bicycles, the bridge is 34 metre in width. As for the double arch steel bridge, it is about 10,000 tons, which equals to the weight of 50 Boeing 747 Jumbo Jets. Its massive size and weight increased the difficulty in transportation. However, the project team tackled the challenge with the use of Building Information Modelling (BIM) and decided to erect the bridge by float-over method at the beginning of last year.
Float-over Erection Raised Speed and Efficiency
To prepare for the erection, a semi-submersible barge loaded with the double-arch steel bridge moved in the temporary anchorage zone in Junk Bay. Sea-fasteners were then removed and temporary supports consisting of 3D jacks were also installed on the bridge piers.
At one day before, the barge moved to an area which was 30 metres from the bridge piers. After observation of tide and wind level, the barge moved in between the bridge piers during high tide window, and moved in between the piers. After fine positioning of the steel bridge, the semi-submersible barge was ballasted to lower the bridge to a pre-determined level above the 3D jack temporary supports. By upward extension of the jacks, the bridge was gradually loaded onto the jacks. Blasting of the barge continued until the erection was completed. The erection process only took 5 hours. This innovative construction method with other cutting-edge technologies were granted the Overall Best Award of ACEHK Annual Awards 2022.
Mr. Kelvin CHAN, resident engineer of consulting firm AECOM, said that the team spent a lot of effort on heavy lifting. By adopting job specific safety measures and clear demarcation of responsibility, all heavy lifting works were done smoothly. He also appreciated the success to prefabrication. To ensure facility management in safe manner, arch rib inspection cradles are tailor-made for inspection and maintenance on arch rib in future.
Safety Standard Enhanced by Digitalisation
The TKO CBL project took only about 4 years to complete with the help of digitalisation. Robotics like welding robots and automatic internal formwork removal robots were widely used throughout the process. The team also adopted the use of Smart Watch Safety System. Mr. MA Sze-kit, Safety Manager of China Road and Bridge Corporation, is one of the users of the system. It does not only facilitate site communication, but also provides functions like measurement of body temperature, heart rate monitoring, fall detection and SOS notification.
Electronic Site Inspection System (E-SIS) is another example of digitalisation. It replaces physical forms to reduce the use of paper. Furthermore, it helps monitor progress of different trades and sort out areas to improve. Over 15,000 electronic forms have been issued since its adoption and all data are stored safely in the system which is totally traceable. Alongside with other digital technologies, this had contributed to the winning of the Gold Award of the CIC Construction Digitalisation Award 2021.
Meeting the community’s aspiration, residents in TKO look forward to the commissioning of the CBL on 11 December as it will improve transport network and enhance connection to the community. Ir. Thomas HO, Chairman of the CIC, also believes that this landmark project will encourage the industry to adopt more safety measures and construction innovation. As innovations like digital twin are becoming popular among the industry, he also hopes the quantity, quality, efficiency and speed of future large-scale infrastructures can be enhanced.
