The Tsing Ma Bridge is a bridge in Hong Kong.^[1] It is the world's ninth-longest span suspension bridge, and was the second longest at time of completion.^[2] The bridge was named after two of the islands at its ends, namely Tsing Yi and Ma Wan. It has two decks and carries both road and rail traffic, which also makes it the largest suspension bridge of this type. The bridge has a main span of 1,377 metres (4,518 ft) and a height of 206 metres (676 ft). The span is the largest of all bridges in the world carrying rail traffic.

The 41-metre (135 ft) wide bridge deck carries six lanes of automobile traffic, with three lanes in each direction. The lower level contains two rail tracks and two sheltered carriageways, used for maintenance access and traffic lanes when particularly severe typhoons strike Hong Kong and the bridge deck is closed to traffic.^[3]

History

Construction of the bridge was carried out by a Costain / Mitsui / Trafalgar House joint venture.^[4] Construction work of the bridge began in May 1992 and ended in May 1997. It cost HK$7.2 billion. The Lantau Link, of which the bridge is an integral part, was opened on April 27, 1997. The ceremony was inaugurated by the former British Prime Minister Margaret Thatcher.

Operation

The Tsing Ma Bridge links Tsing Yi island on the east to Ma Wan island on the west over Ma Wan Channel. It is part of the Lantau Link, which, with two long span bridges links the New Territories and Lantau Island, and eventually leads to the Hong Kong International Airport on Chek Lap Kok via North Lantau Highway. The other bridges are the Kap Shui Mun Bridge linking Ma Wan to Lantau Island over Kap Shui Mun and the Ting Kau Bridge linking Tsing Yi to the New Territories over Rambler Channel.

The Tsing Ma Bridge has been an important gateway to Lantau Island. It is Route 8 expressway, which connects the Lantau Link, the West Kowloon expressway, Cheung Sha Wan and Shatin. The rail line is part of MTR's Tung Chung Line and Airport Express. The Noah's Ark attraction is located next to the bridge.^[5]

The bridge, together with other highway, bridge and tunnel connections in the area, are part of the Tsing Ma Control Area under the Tsing Ma Control Area Ordinance (Cap. 498) in Hong Kong Law.^[6] The control area has been managed by Tsing Ma Management Limited since opening. The control area's traffic management system was developed by Delcan Corporation of Toronto. Special regulations and by-laws are carried out in the area.

Along with the Ting Kau Bridge and Kap Shui Mun Bridge, the bridge is closely monitored by the Wind and Structural Health Monitoring System (WASHMS). Surveillance cameras are also installed over the bridge to record traffic conditions. The video is available at the government website.^[7] It is updated every two minutes.

Toll payable on the Lantau Link—of which Tsing Ma Bridge is part—for motorcycles, private cars, public double-decker buses and heavy goods vehicles are HK$20, $30, $60 and $80 respectively, and payable only for the eastbound direction from Lantau to Tsing Yi.^[8] The normal speed limit on the bridge is 80 km/h, subject to lowering in the event of road work or strong wind. Traffic may also be directed to the sheltered carriageways on the lower deck when there are very strong winds. There is no sidewalk on the bridge. Parking is also prohibited on the bridge.

Design

The bridge was designed by Mott MacDonald.^[9]

Wind tunnel testing

The objectives of the wind tunnel studies were to demonstrate the safety of the structure under construction and once completed, both with respect to aerodynamic stability as well as the possible effects of extreme typhoon wind speeds. A further objective was to provide dynamic response data at several key locations to compare with full scale data from the ongoing monitoring program, conducted by the Highways Department of Hong Kong.

A 1 to 80 scale section model of the deck in the erection stage, and a 1 to 400 scale full aeroelastic model of the entire bridge were constructed. It is a Monte-Carlo simulation of the typhoon wind climate. The full model was tested in different stages of construction in turbulent boundary layer flow, complete with the local topography in order to model the wind conditions at the site. The model tests identified critical stages of erection that allowed the construction schedule of the bridge to be tailored to avoid the typhoon season. The comparison of model test results and the full scale monitoring will assist engineers to better understand the behaviour of long span bridges in wind and to improve current design methods.

Major components

Cable band for Tsing Ma Bridge undergoing dimensional inspection

1. Bridge tower foundations - one tower located on Wok Tai Wan of Tsing Yi side and the other on a man-made island 120 m from the coast of Ma Wan Island.^[10] Both towers are 206m above sea level and founded on relatively shallow bedrock. The towers are two-legged with trusses at intervals, in the form of portal beam design. The legs were constructed with high-strength concrete of 50 MPa (concrete grade 50/20) strength, using a slipform system in a continuous operation.
2. Anchorages - the pulling forces in the main suspension cables is taken up by large gravity anchorages located at both ends of the bridge.^[11] They are massive concrete structures deeply seated on bedrock on the landside of Tsing Yi and Ma Wan island. The total weight of concrete used in the Tsing Yi anchorage is 200,000 tonnes and Ma Wan Anchorage is 250,000 tonnes.
3. Main cables - The cables were constructed by an aerial spinning process. The process involved drawing wires from a constant-tension supply, and pulling loops of these wires from one anchorage to the other, passing a 500-tonne cast-iron saddle on top of each bridge tower seating the cable. A total of 70,000 nos. galvanised wires of 5.38 mm diameter were placed and adjusted to form the 2 nos. of 1.1 m diameter main cables.
4. Suspended deck - The steelwork for the deck structure was fabricated in Britain and Japan. After delivery, they were further processed and assembled in Dongguan of China into standard deck modules. A total of 96 modules, each 18 m long and about 480 tonnes in weight, were prepared. These deck modules were brought to the site by specially designed barges and raised into the deck position by a pair of strand jack gantries that could manoeuvre along the main cable.
5. Approach span on Tsing Yi side - similar in form and cross-section to the suspended deck, but the approach span was supported on piers instead of cable-support. The first span was assembled on the ground and raised into position using strand jacks. Further erection then proceeded in cantilever in smaller sections, using derrick cranes stationed on the deck level. An expansion joint which allowed for a maximum thermal movement of ± 835 mm was also provided and located inside the approach span section. This was designed and provided by the Swiss Civil Engineering firm mageba.^[12]

Sumber :

http://en.wikipedia.org/wiki/Tsing_Ma_Bridge