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| (b) |
Wind Tunnel Tests – As with the design of all long span bridges, aerodynamic considerations require extensive analysis and wind tunnel testing was carried out as follows: |
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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. |
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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 .
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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 . |
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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. |
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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 . |
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| (c) |
Turbulence Intensity Measurement - As part of the design of the Stonecutters Bridge one of the key considerations was the wind loading to which the bridge is exposed. In order to ascertain the loading, the wind climate at the bridge site was thoroughly investigated by means of wind tunnel tests and site measurement.
It was necessary to develop site-specific wind loading for the structural design of Stonecutters Bridge . To achieve this, field measurements were carried out to collect information on the wind speed, wind profile and wind turbulence at the CT8 side. Terrain model wind tunnel tests were carried out to complement the field measurements and to extend the coverage to include the CT9 side and the areas in between. |
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Terrain Model Testing
The approaches to the bridge are over terrain varying from open water to mountains and built-up areas. To establish the atmospheric turbulence characteristics at the bridge site and to correlate wind data from various specific locations for different wind directions, wind tunnel terrain model tests consisting of a 1/1500 scale model of the topographical terrain surrounding Stonecutters Bridge were conducted. The terrain coverage was within approximately 9 to 10km radius from the proposed bridge site. |
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Field Measurement
Wind Turbulence Intensity Field measurements were carried out to measure the wind climate at the bridge site. The objective is to carry out field measurements of atmospheric wind speed, direction and turbulence in order to obtain information on the vertical mean wind profile, horizontal mean wind inclination and one-point spectra prevailing at a location near the bridge site. The fieldworks, included the construction of a 50m high mast structure and provision of anemometers, barometers, hygrometers, and thermometers at both 30m and 50m above ground. A data logger and analyser were also provided. The mast structure is located close to the future position of the tower on Container Terminal 8. |
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| (d) |
Marine Aspects -
Clearance Requirements
The bridge will straddle the Rambler Channel at the entrance to the Kwai Chung Container Port. In order to allow for adequate airdraft for the passage of super container vessels of the next generation, the soffit level of the bridge is set at a minimum level of 73.5 mPD. It will make the Stonecutters Bridge deck one of the highest in the world.
Navigation Simulation Workshop
One of the critical design constraints is to ensure the passage of vessels at all times during the construction of the bridge, and most critically, during the lifting of deck units from the channel. Pilots from the Hong Kong Pilots Association Ltd (HKPA) generally guide major vessels, such as container ships, into the port. A navigation simulation workshop was held in early July 2001 for the pilots from the association to become familiar with possible restrictions during construction of the bridge. Using real time simulation software at the workshop, the pilots navigated into and out of various berths during the lifting of deck units from different locations within the channel.
Ship Impact Tests
As the tower’s foundation will be located less than 10m away from the existing seawall coping lines of Container Terminal 8 and the proposed Container Terminal 9, ship impact is a significant load scenario for the design of Stonecutters Bridge. To model the complex soil/structure interaction during impact of ship, geotechnical centrifuge model testing using a 1:200 scale model of a vessel bow and seawall within a container was adopted to carry out the centrifuge testing. The container was then put into a calibrated centrifuge and spun at a centrifugal acceleration of 200 time gravity (200g).
 
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| (e) |
Detailed Design - The bridge was designed using sophisticated computer software to simulate the behaviour under different loading conditions through construction and for the full service life. Each stage of the construction process was modeled, as well as the complex effects of the wind environment, potential seismic events, and the patterns of traffic loading. A global model of the full bridge was used to determine the effects caused. This was updated at key phases to reflect the latest information as the design evolved. Very detailed local finite element models were used to determine stress flows in different parts of the bridge and supplement the global results. A rigorous verification was made to confirm the safety and performance of all structural components and compliance with the statutory design standards. |
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| (f) |
Design Development - The design of Stonecutters Bridge is developed from the Reference Scheme (RS) with the objective of keeping its appearance. The main changes to the RS were: |
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Deletion of the monolithic joint between the deck and the tower to reduce the torsional moment in the tower during the full cantilevering of the bridge as well as in-service. |
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Introduction of lateral bearings and longitudinal hydraulic buffers at the towers to cater for the horizontal wind loads and short term dynamic loading such as that from wind and seismic effects respectively. |
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Use of parallel wire stay cables instead of locked coil cables. |
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Change of deck cross-section shape from a fully curved soffit to a combined curve and straight soffit. |
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Modification of the top 118m portion of the tower from a steel only cross-section to a steel-concrete composite section to provide greater stiffness and damping. |
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Design Competition - An international design competition organized by Highways Department of the Hong Kong Special Administrative Region (HKSAR) was held in 2000. The winning design was highly praised for its aesthetic merits. It is a bold yet simple scheme. The winning design concept was chosen as the Reference Scheme (RS), and further developed during the detailed design stage. 
