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FIND OUT MORE. Architecture 328–329 • Computers 190

Science and Technology^203

An engineer applies the principles of science to the design of

structures and machines. Structural engineers, for example, make

calculations to predict the stability of structures. Civil engineers

plan the construction of railways, roads, and dams.

ENGINEERING

2 BRIDGES

These bridges are some of the

most beautiful engineering

structures. They are carefully

designed to carry heavy loads,

and survive bad weather.

HOW DOES A BRIDGE CARRY A LOAD?

A straight beam bends in the middle as it

supports a load. A beam bridge can carry a

load over a narrow gap, but a longer bridge

needs a stronger shape. An arch supports

the load from beneath – it directs the force

around the curve to push against the

ground at both sides. A suspension bridge

supports a load from above, with cables.

HOW HIGH CAN A SKYSCRAPER GO?

The Burj Khalifa in Dubai opened in 2010. It

stands at a height of 828 m (2,717 ft) and is the

tallest skyscraper in the world. Engineers could

build even taller structures, but higher buildings

cost more money and need to be made safe.

WHAT IS THE BEST SHAPE FOR A DAM?

A dam holds back water in a river to form an artificial

lake. Water pressure increases with depth, so the

greatest pressure on the dam is at its base – the dam

wall is much thicker at the bottom than at the top.

1 CURVED DAM

The curved shape of this concrete

dam gives it strength. The water

pressure is directed around the

curve, which pushes against

the high ground at either side,

so the ground takes some of the

pressure away from the dam.

Concrete and

steel frame will be

clad (coated) with

glass so that it

looks attractive,

and windows will

be glazed

ARCH BRIDGE CABLE-STAYED BRIDGE CANTILEVER BRIDGE SUSPENSION BRIDGE

HOW IS A TUNNEL BORED?

Tunnels are cut with tunnel boring machines (TBMs),

burrowing through the ground. As their cutting blades

turn, the machines move forward at an average rate

of about 1.6 km/h (1 mph). Engineers line the tunnel

behind the TBMs with reinforced concrete rings to

prevent the roof and walls from collapsing.

1 TUNNEL DIGGING

Each of the six TBMs used to dig

the Anglo-French Channel Tunnel

was pushed forwards on rails with

a force of 420 tonnes. As the

TBM worked, conveyor belts

following behind carried away

1,000 tonnes of clay and rubble

each hour.

construction