Vasco da Gama Bridge

From Wikipedia, the free encyclopedia

Vasco da Gama Bridge

Official name	Ponte Vasco da Gama
Carries	Six road lanes
Crosses	Tagus River
Locale	Sacavém, north of Lisbon (right bank) Municipality of Montijo (left bank)
Maintained by	Lusoponte [1]
Design	cable-stayed, viaducts
Longest span	420 m (1,378 ft)
Total length	17.2 km (10.7 mi)
Width	30 m (98 ft)
Opening date	March 29, 1998
Maps and aerial photos

The Vasco da Gama Bridge (Portuguese: Ponte Vasco da Gama, pron. IPA: ['põt(ɨ) 'vaʃku dɐ 'gɐmɐ]) is a cable-stayed bridge flanked by viaducts and roads that spans the Tagus River near Lisbon, capital of Portugal. It is the longest bridge in Europe, with a total length of 17.2 km (10.7 mi), including 0.829 km (0.5 mi) for the main bridge, 11.5 km (7.1 mi) in viaducts, and 4.8 km (3.0 mi) in dedicated access roads. Its purpose is to alleviate the congestion on Lisbon's other bridge (25 de Abril Bridge), and to join previously unconnected motorways radiating from Lisbon.

The bridge was opened to traffic on March 29, 1998, 18 months after construction first began, just in time for Expo 98, the World's Fair that celebrated the 500th anniversary of the discovery by Vasco da Gama of the sea route from Europe to India.

The bridge carries six road lanes, with a speed limit of 120 km/h (75 mph), the same as motorways, except on one section which is limited to 100 km/h (60 mph). On windy, rainy and foggy days, the speed limit is reduced to 90 km/h (56 mph). The number of road lanes will be enlarged to eight when traffic reaches a daily average of 52,000.

Bridge sections

North access roads
North viaduct - 488 m (1,601 ft)
Expo viaduct - 672 m (2,205 ft); 12 sections
Main bridge - main span: 420 m (1,378 ft); side spans: 203 m (666 ft) each (total length: 829 m/2,720 ft); cement pillars: 150 m (492 ft)-high; free height for navigation in high tides: 45 m (148 ft);
Central viaduct - 6.351 m (20.84 ft); 80 pre-fabricated sections 78 m (256 ft)-long; 81 pillars up to 95 m (312 ft)-deep; height from 14 m (46 ft) to 30 m (98 ft)
South viaduct - 3.825 m (12.55 ft); 45 m (148 ft) sections; 84 sections; 85 pillars
South access roads - 3.895 m (12.78 ft); includes the toll plaza (18 gates) and two service areas

The project was split in four parts, each one built by a different company, and supervised by an independent consortium. There were up to 3,300 workers simultaneously on the project, which took 18 months of preparation and another 18 months of construction.

The bridge has a life expectancy of 120 years, having been designed to withstand wind speeds of 250 km/h (155 mph) and hold up to an earthquake 4.5 times stronger than the historical 1755 Lisbon earthquake (estimated at 8.7 on the Richter scale). The deepest foundation piles, up to 2.2 m (7.2 ft) in diameter, were driven down to 95 m (312 ft) under mean water level. Due to the bridge's length, it was necessary to take the Earth's curvature into account to site the piers correctly, otherwise a deviation of 80 cm (31 in) would be apparent at either end of the bridge. Environmental pressure throughout the project resulted in the left-bank viaducts being extended inland to preserve the marshes underneath, as well as the lamp posts throughout the bridge being tilted inwards so as not to cast light on the river below.

The cost of the bridge came at zero to the State, as it was built in the BOT (build-operate-transfer) system by Lusoponte, a private consortium which got a 40-year concession on the tolls of both Lisbon bridges. Lusoponte's capital is 50.4% from Portuguese companies, 24.8% French and 24.8% British.

As of 2007, the toll is €2.20 per passenger car, northbound (into Lisbon). There is no toll for southbound traffic.