Kap Shui Mun Bridge

The Kap Shui Mun Bridge (KSMB) in Hong Kong, part of Lantau Link of Route 8, is one of the longest cable-stayed bridges in the world that transports both road and railway traffic, with the upper deck used for motor vehicles and the lower deck for both vehicles and the MTR. It has a main span of 430 m and an overall length of 750 m. It spans the Kap Shui Mun marine channel between Ma Wan and Lantau islands and has a vertical clearance of 47 m above sea level. The bridge was completed in 1997.

Structural information
The total length of the Kap Shui Mun Bridge includes a 70 m approach span on the Lantau side. There is a column in each of the back spans of the cable stayed bridge, making four 80 m spans, adding to the 430 m main span. This makes the total length 820 m. The 503 m Ma Wan Viaduct was constructed under the same contract as the KSMB. The viaduct connects the KSMB to the Tsing Ma Bridge, forming the Lantau Link, which was built to provide access to the new airport. The navigation clearance of 47 m is part of the reason that the H-shaped towers are 150 m tall.

The Kap Shui Mun Bridge is not symmetrical, in that the 160 m back span length (two 80 m spans) is less than half of the main span length (which would be 215 m). To provide the balance that symmetry will normally provide, part of the bridge has a composite structure. The center 387 m of the main span uses a steel-concrete composite to make the structure lighter. The back spans and the rest of the main span are concrete. Using the lighter steel cross section in the majority of the main span serves to equalize the horizontal forces on the towers and balance the bridge.

Because the lower deck carries both rail and traffic, the cross section is designed as a Vierendeel truss. This means that there are no diagonal members in the cross section and that vehicles and rail cars drive through the openings provided by the Vierendeel design.

Along with the Tsing Ma Bridge and Ting Kau Bridge, it is closely monitored by the Wind and Structural Health Monitoring System (WASHMS).

Concrete strength of towers: Grade 50/20 or 50MPa

Crane strike
The bridge has a height restriction of 41 metres for vessels passing underneath. On 23 October 2015, a barge attempted to pass under the bridge with a broken-down crane that could not be lowered. The crane had a maximum height of 43 metres, but was tilted slightly to 41 metres. The bridge has an actual clearance of 47 metres, but potentially due to the high tide and wave action, the crane struck the bridge and damaged its underside. The Tsing Ma Bridge has a higher height clearance of 53 metres but a source said the captain of the tugboat towing the barge may have opted to take Kap Shui Mun to save time.

The strike triggered the Ship Impact Detection System to issue an alarm and both the road and railway were shut down immediately, severing Lantau Island and the airport from the city from about 7:40 pm to 10:00 pm. The government's contingency plan to implement emergency ferry service between Tsuen Wan and Tung Chung failed as the ferry operator took almost two hours to ready the service. Some travelers attempted to reach the airport via the Discovery Bay Ferry Pier, although many missed their flights.

The Highways Department inspected the bridge and found that only the inspection platform rails were damaged by the collision, and that the structural integrity of the bridge was not jeopardised. In the days following the incident there were calls in local media for the government to build a second link to the airport. In fact, such a link was already under construction: the Tuen Mun–Chek Lap Kok Link road tunnel was being constructed as part of the Hong Kong–Zhuhai–Macau Bridge project. This opened in 2020.