Bosphorus Bridge (1973, Turkey).

Apart from new types of structures, innovative technologies such as pre-stressed concrete technology were put into use in bridge construction engineering of the past century. Gladesville Bridge across the Parramatta river, erected in 1964, was built employing the above-mentioned technology. It is an arch bridge made of multi-dimensional elements cast in concrete according to Roman vault construction principles. The horizontal curvature used by means of the main girder provided the required space for inland navigation and made it possible to balance the whole structure. An example of an impressive, streamlined bridge is the suspension bridge over the Bosphorus strait in Istanbul connecting the European and Asian part of the city. Upon its commissioning in 1973, it was the fourth longest span bridge in the world and the longest one outside the United States. The suspended span is 1,074 m long and its pylons are founded on the ground. Suspended side spans were replaced by two short access viaducts. When it opened in 1997, Tsing Ma in Hong Kong was the second longest span suspension bridge in the world. The massive structure of the bridge was forced by the design taking into account a three-lane motorway on the deck and a double track railway line running inside the steel main girder.

Alamillo Bridge in Seville (1992, Spain).
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Puente de La Mujer – Women’s Bridge (2001, Argentina).
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Sundial Bridge in Redding, California (2004, USA).

The crossing through the Great Belt in Denmark is an 18-kilometre suspension bridge connecting two islands – Zealand and Funen. This complex, built from steel and reinforced concrete, was commissioned in 1998 and is one of the most magnificent and longest bridges in Europe. The suspended part is 2.7 km long and pylons are spaced at 1,624 m. Every pylon is 281 m tall, of which 254 m is above the water table.

An impressive cable-stayed bridge deemed a work of art is Ponte Vasco da Gama in Portugal – the largest and longest reinforced concrete bridge in Europe with characteristic H-shaped pylons. The bridge with the main span of 420 m was designed by Armando Rito. The structure was commissioned in 1998 during the international fair EXPO’98 to celebrate the 500th anniversary of the discovery of the sea route from Europe to India by the famous Portuguese sailor.

Two clearly leading trends could be observed in the 20th century bridge design – steel structures and later pre-stressed concrete bridges. What is the future of bridge construction?
 
In 21st century bridge engineering we are dealing with new materials that are mainly polymers reinforced with heavy-duty fibres, aluminium, and glass. Their task is also relieving load from the structure. At present, most designers pay attention to the beauty but also ‘smartness’ of the structures equipping them, e.g. with fibre optic sensors which facilitate monitoring and transmission of important information, for example, about the tension of the structure. Aesthetic design, although significant, is not the key criterion. Nowadays – observing all rules of engineering art – the priorities to be taken into account are safety and user requirements and needs.
Highway in Atlanta.
Road interchange in Osaka.
Oresund Bridge across the Sund (2000, Denmark-Sweden).
Vasco da Gama Bridge (1998, Portugal)

A new type of bridge was built between two countries – Denmark and Sweden over the lower part of the Sound. The cable-stayed road and railway bridge, officially opened on 1 July 2000, is in fact a complex comprising a bridge, tunnel and artificial island. Oresund is the longest bridge in Europe (7,845 m) and it has two levels – the lower one is reserved for railway traffic and the upper one carries four lanes of the trans-European road E20.

A tilt footbridge connecting two twin cities – Newcastle and Gateshead – has received many awards for its original design and functionality. This original footbridge for pedestrians and cyclists was put into use in 2001. It has a 105 m long span, and the total length of the bridge is 126 m. The six hydraulic lift arms with a diameter of 45 cm, powered with 55 kW electric motors, tilt the structure forming a 25-metre clearance for inland navigation.

Infinity Bridge – a pedestrian and cycle footbridge (2009, England)
Rio-Antirrio Bridge (2004, Greece).
Banpo Bridge in Seoul with the world’s longest illuminated fountain.
Millau Viaduct (2004, France).

At present, one of the tallest bridges in Europe (343 m tall pylons) is the Millau multi-span cable-stayed bridge in France. It spans over the length of 2,460 m. It consists of seven piers of different height, whereas above the deck all pylons always have the same height, that is, 87 metres.

The bridge that changed the previous outlook on cable-stayed structures is the Rion-Antirion Bridge in Greece (built in 2004). Erected at the narrowest point of the Gulf of Corinth, it not only connects two coasts but also two different tectonic plates. The cable-stayed part spans over the length of 2,252 m, while the total length of the bridge is 2,880 m. Such a large span is due to the fact that the bridge has no rigid connection to pylons and it is only fastened by means of hydraulic dampers reducing dynamic movements caused by the seismic activity of the region. What is more, four main pylon supports are not deeply founded on piles in the sea bottom but they are built atop massive caissons to prevent the collapse of the bridge. Also, the feet of the pylon are slanted at the top forming two frames bending over to each other, resembling the letter A, to increase the resistance of the structure to earthquakes.

Road engineering is developing intensely in the 21st century. Present-day technologies, professional know-how and high-tech materials make it possible to make durable surfaces which, if handled correctly, will be used for many years. Currently, selecting road layer design solutions, concrete surfaces are given priority. It is estimated that in the world about 5% of roads are concrete roads, although in European countries this ratio is considerably higher. The advantages of utility concrete are its large bearing capacity, high durability, resistance to rutting, bright colour increasing driver safety and lower maintenance cost.

Modern road junction in Dallas, USA.
BEIJING, CHINA - OCTOBER 06:  (CHINA OUT) (EDITORS NOTE: Image captured with a fisheye lens) Aerial view of cars queuing up to pass a checkpoint set recently in the direction of Beijing on the Beijing-Hong Kong-Macau Expressway at the end of National Day Holiday on October 6, 2015 in Beijing, China. A travel peak appeared at the end of 7-day China's National Day Holiday.  (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)
Record traffic jam on Hong Kong – Beijing Motorway in China.
Modern road junction in the USA.
Viaduct on Rodovia dos Imigrantes (Immigrant Road) in Brazil.