Massive and monumental Stonecutters Bridge soars above Hong Kong’s skyline, providing eye-catching proof, if there was any doubt, of the city’s prowess as one of the world’s greatest centers of commerce.
Completed in December 2009, the bridge spans the Rambler Channel at the entrance to the Kwai Chung container terminals and is a linchpin in the new Route 8 strategic road link connecting western Kowloon to the international airport. Stonecutters measures 1.6 kilometers from end to end, but it’s the 1,018-meter cable-stayed span that makes record books as the third longest in the world. The cables are supported by two 293-meter mono towers, the top 118-meter of which is a composite structure – an inner concrete core wrapped in an outer layer of stainless steel.
According to Arup, the engineering company that designed and built the bridge, as much as 1,600 tonnes of structural stainless steel went into the bridge’s cable-stay anchorage zone.
Arup quickly dismissed carbon steel for the bridge’s critical tower sections as it just wasn’t durable enough for the job. In addition to figuring out what material would be able to hold up the anchoring the cables under normal conditions, engineers had to consider typhoon-force winds and the possibility that a wayward ship could ram the base of the towers.
As the customer had called for a 120-year lifespan for the bridge, choosing the right material for the tower tops was a must.
The company opted to sheathe the towers in Outokumpu’s high-strength Forta duplex stainless steel quarto plate. With roughly double the strength of austenitic grades, duplex is a popular choice where strenght is a critical factor. Outokumpu duplex stainless steel tubes and plates were also used to form the cable anchoring boxes.
Beauty for the ages
Enduring the day-to-day conditions above the Rambler Channel can be a challenge in itself. Hong Kong’s hot, moist weather and sea air make the perfect atmosphere for corrosion, a process further intensified by pollution from the heavy ship traffic in the area.
As the customer had called for a 120-year lifespan for the bridge, choosing the right material for the tower tops was a must. If carbon steel were used, the periodic maintenance needed to recoat it would have been a major undertaking, especially considering the busy roadway below. Using corrosion-resistant Forta duplex stainless steel, however, makes the tower tops practically maintenance free, keeping the Stonecutters Bridge looking every bit as amazing from decade to decade as it did on its opening day.