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Stonecutters Bridge

 
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Dr. N. Subramanian
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PostPosted: Fri Nov 26, 2010 6:55 pm    Post subject: Stonecutters Bridge Reply with quote

Stonecutters Bridge





Designer      Dissing+Weitling, design competition winner

Height      298 m (978 ft)
Longest span      1,018 m (3,340 ft)
Clearance below      73.5 m (241 ft)




Stonecutters Bridge is a 1,596 metre long dual 3-lane high level cable stayed bridge, with a clear span of 1,018 metres. It is a major part of the section of Route 8 between Tsing Yi and Cheung Sha Wan. The bridge will straddle the Rambler Channel at the entrance to the busy Kwai Chung Container port. It will be situated at the back-up land of the Container Terminal 8 (CT8) at the eastern side on Stonecutters Island. At the western side it will be built on the back-up land formed for Container Terminal 9 (CT9) on Tsing Yi Island.  The  bridge deck was completed on 7 April 2009, making this the second longest cable-stayed span in the world. It opened to traffic on 20 December 2009.

The approaches at Tsing Yi and Stonecutters Island are located near Container Terminal 9 and Container Terminal 8, respectively. Construction commenced on 27 April 2004 by Maeda–Hitachi–Yokogawa–Hsin Chong Joint Venture. It cost HK$2.76 billion. It was reported to be over budget.

The bridge is part of Hong Kong's Route 8, connecting Sha Tin, Cheung Sha Wan, Tsing Yi Island, Ma Wan and Lantau Island. Other major constructions along the route are Nam Wan Tunnel (completed in 2008), Eagle's Nest Tunnel (completed in 2008), Sha Tin Heights Tunnel (completed in 2008), Tsing Ma Bridge (completed in 1997) and Kap Shui Mun Bridge (completed in 1997).

As a result of the interesting challenges and extreme difficulty in constructing this bridge, the project was featured on the Discovery Channel's Extreme Engineering series on April 27, 2009.


Structure

The bridge spans 1.6 km, with 3 lanes in each direction. It is a cable-stayed bridge with two bridge towers, one on Tsing Yi Island and the other on Stonecutters Island.

With a main span of 1,018 m, Stonecutters Bridge has the second-longest cable-stayed span in the world, after the Sutong Bridge.

It was built at a cost of HK$2.76 billion (US$356 million).


Bridge design

The design concept for the bridge was procured by Highways Department in Hong Kong through an international design competition. The winning scheme was the one presented by a group consisting of bridge architect Dissing+Weitling together with engineering firms Halcrow Group, Flint & Neill Partnership and Shanghai Municipal Engineering Design Institute. The design was selected as the Reference Scheme for the further design development. A group led by Arup with COWI A/S as main sub-consultant has carried out the further design development of the Reference Scheme and the detailed design that followed.

The concept is for a cable-stayed bridge with a twin aerodynamic deck suspended from two 295m-high single pole towers. These towers will have bases measuring 24m x 18m tapering to 7m diameter at the top, and the deck will allow a navigation clearance of 73.5m over the full entrance to the Container Port.

The two towers will be in concrete until level +175m and in composite construction consisting of an inner concrete ring with a stainless steel skin for the top 120m. The original concept had a conventional steel structure above level +175m but Arup found that this configuration would be too lively and lead to unacceptable vibrations of the stay cables. Using a heavier composite section instead of a pure steel structure solved this problem. For reasons of durability and to enhance the appearance, further studies concluded that the tower skin should be fabricated from a duplex stainless steel (grade 1.4462 to BSEN10088) with a shot peened surface finish. The deck itself will be made of steel in the main span and of concrete in the side spans.

The tower foundations are located within 10m of the seawall on either side of the Rambler Channel, close to the back-up land next to CT8 and CT9. Their proximity to the channel necessitated ship impact testing and modeling. Geotechnical centrifuge testing was conducted using a 1:200 scale model of a vessel bow section and seawall within a container.

Wind studies

The Hong Kong region is susceptible to very strong typhoon winds, a fact that is being taken into account in the design of the bridge. In October 2002 a 50m mast was erected at the site to measure the speed, direction and turbulence of winds in the area. Readings, which continued until January 2004, were transmitted in real-time to an offsite location for further analysis. In particular, the stability of the 509m-long cantilevers during construction required special consideration in the design.
     

1:80 Standard Section Model Tests

These tests were carried out to investigate the vortex shedding response and steady wind load coefficients of the deck section. The effect of guide vanes and variations in girder edge geometry were also investigated. The tests were conducted by the Danish Maritime Institute.
1:20 Section Model Tests

The purpose of these tests was to verify the aerodynamic performance of the deck section determined from the 1:80 standard section model tests. By modelling the deck section in a larger scale a more accurate shape and position of the guide vanes was determined. The tests were carried out at the National Research Council in Canada .
     
       
Full Aeroelastic Tower Model Tests

The purpose of these tests was to investigate the tower's vortex shedding response and to determine the measures necessary to reduce the response to acceptable levels to minimise the risk of cable vibrations. A 1:100 full aeroelastic tower model was constructed to study the response of the tower under various wind conditions. The tests were carried out in Denmark .
     
       

Stay-Cable Testing
The stay-cable will be subject to the effects of wind and rain and will affect the bridge in two ways:

- The drag load coefficient of the cables will be directly reflected in the horizontal load carrying capacity of the bridge.

- Large amplitude oscillations induced by the combined effect of wind and rain may introduce wear and fatigue damage to cable attachments and cause concern to motorists travelling on the bridge.

- Wind tunnel tests were carried out to investigate the susceptibility of stay cables to rain-wind induced vibrations and verify the effectiveness of various mitigation measures in minimising such rain-wind induced phenomenon.
     
       
Full Aeroelastic Bridge Model Testing

The Full Aeroelastic Bridge Model Tests were carried out to measure the buffeting response to turbulent wind and susceptibility to aeroelastic flutter and galloping instabilities of the bridge. Measurements in the service condition and in selected construction stages with topographic proximity were carried out in Monash University in Melbourne , Australia .

See Videos:
http://www.youtube.com/watch?v=7YSdKKTchDE
http://www.youtube.com/watch?v=GXoiqwUIxfE&feature=fvw

It received the Instn. Of Structural Engineers, UK Award for 2010.
(http://www.istructe.org/thestructuralengineer/#)
References:
http://www.stonecuttersbridge.net/en/main.htm
http://en.wikipedia.org/wiki/Stonecutters_Bridge
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