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Hong Kong has added a new prominent feature to the city: Stonecutters Bridge, opened to traffic on December 20th, 2009.
Stonecutters is one of the biggest road bridges in the world and one of only two cable-stayed bridges with a span of more than one kilometre. Dominating Hong Kong’s skyline, the bridge echoes Hong Kong’s image as one of the most cosmopolitan and vibrant cities in Asia.
The bridge straddles the Rambler Channel at the entrance to the Kwai Chung container terminals, providing a landmark gateway to this dynamic trade centre. The crossing forms a central part of the new Route 8, linking Cheung Sha Wan and Tsing Yi Island.
In construction since 2004, Stonecutters Bridge has been a challenging task and marks a major milestone in bridge engineering.
The Highways Department of the Hong Kong Special Administrative Region organized an international design competition for the bridge in 2000. The winning design was by an international partnership, formed by Halcrow Group, Flint & Neill Partnership, Dissing + Weitling and Shanghai Municipal Engineering Design Institute. The design was highly praised for its aesthetic merit, hailed as a bold yet simple scheme. This Reference Design was developed by a group led by Ove Arup and Partners Hong Kong Limited, who carried out the detailed design and handled construction supervision.
Stonecutters Bridge is a cable-stayed bridge with a twin aerodynamic deck suspended from two single-pole towers reaching the level of 298mPD (metres above Principal Datum). The towers are in reinforced concrete up to level 175mPD and, for the top 118m, they are in a composite section consisting of an inner concrete core and stainless steel on the outside, connected by shear studs. The heavy composite structure, instead of a conventional steel structure, provides necessary stiffness and damping for the stay cables. The stainless steel provides a striking aesthetic effect, visible from the commercial centre on Hong Kong Island.
The owner requested a 120-year design life for the bridge. Carbon steel offered the necessary structural strength but not the durability needed for the towers. Arup considered various alternatives to carbon steel and concluded that the appropriate material was the high-strength duplex stainless steel 1.4462 (2205).
Duplex stainless steels are today preferred for a broad range of structural applications owing to their high strength – close to double that of austenitic grades. The hot, humid and maritime environment of Hong Kong required a material with high corrosion resistance, which can also be provided by duplex 1.4462 to render the tower tops maintenance-free – a major consideration for the bridge operators because of the difficulty of accessing these sections.
Outokumpu won the Stonecutters Bridge duplex stainless steel sub-contract for the towers in 2004 and completed the supply of polished plates with 1K surface in 2006. Final surface finishing was carried out by a fabricator in China. Outokumpu followed up with technical support during construction.
Outokumpu also supplied duplex stainless steel tubes and plates for the anchoring boxes of the bridge’s cables.
“Stonecutters Bridge is further proof of our skills and the capabilities of our international team to deliver for the most demanding structural projects in the world,” says Anders Finnås, Outokumpu’s Segment Sales Manager for architectural and structural applications.
“The current trend of using high-strength duplex stainless steel in bridges is increasing rapidly,” Finnås continues. “Durable composite structures such as concrete and high-strength duplex grades are particularly applicable in harsh service environments with warm, humid and saline air and sea spray.
“The range of duplex grades available today provides designers and engineers with many alternatives to build lightweight, sustainable and low-maintenance bridges for long service lives.”
Outokumpu offers high flexibility in its range of duplex stainless steel tubes and plates available for bridges, capable of supplying customized sizes of almost any dimensions within a certain framework. This reduces waste at the mill and further down the supply chain, for the benefit of both the customer and the environment. |