3 Building Big Bridges

Building Big Bridges written by John Lockyer

约翰·洛克耶写的《建造大桥

Big bridges carry vehicles and people over water, valleys, roads, and railways. They help people to get from one place to another. Big bridges must be made of materials that won't bend, crack, or crumble. Most big bridges are built of concrete or steel because these materials are strong enough to last a long time.

大桥承载着车辆和人在水面、山谷、公路和铁路上通行。 它们帮助人们从一个地方到另一个地方。 大桥必须用不会弯曲、不会破裂、不会崩塌的材料建造。 大多数大桥都是用混凝土或钢建造的，因为这些材料足够坚固，可以使用很长时间。

bridge-building Before a new bridge is built, bridge-builders work out how long and how high it needs to be. They look at the land and any water the bridge will cross. They think about how many vehicles and people will use the bridge. There are many different sizes and shapes of bridges in the world. There are bridges that swing and lift and float, but there are really only four kinds.

在建造一座新桥之前，建造桥梁的人会计算出桥的长度和高度。 他们看着陆地和桥梁将要经过的水域。 他们考虑有多少车辆和人会使用这座桥。 世界上有许多不同大小和形状的桥梁。 有可以摆动、升降和漂浮的桥，但实际上只有四种。

beam bridge A beam bridge is made of one or more pieces of concrete or steel. The beams are held up at each end by the ground or by piers, which are the bridge supports. A long beam bridge is held up by piers in the middle. This beam bridge in Sweden carries vehicles across the water. It makes the journey much shorter for the traffic.

梁桥是由一块或多块混凝土或钢制成的。 梁的两端由地面或桥墩支撑，桥墩是桥梁的支撑物。 一座长梁桥由中间的桥墩支撑着。 这座位于瑞典的梁桥承载着水上的车辆。 对于交通来说，这使旅程缩短了很多。

arch bridge An arch bridge is built from stone, brick, concrete or metal. Huge blocks and piers are placed at each end and sometimes in the middle of the bridge. After cranes lift the arches onto the blocks, a road is built between the piers. An arch bridge is strong because all the weight on the arch is spread along the curve to the ground. This stone arch bridge in France was built more than two thousand years ago. There were no cranes to help with bridge-building then!

拱桥是用石头、砖、混凝土或金属建造的。 巨大的石块和桥墩被放置在桥的两端，有时也放置在桥的中间。 起重机将拱门吊起到桥墩上后，在桥墩之间修建一条道路。 拱桥很坚固，因为拱桥上的所有重量都沿着曲线扩散到地面上。 法国的这座石拱桥建于两千多年前。 那时还没有起重机来帮忙建桥!

suspension bridge A suspension bridge has a road that hangs from strong steel cables. The cables are held up by tall towers. Each cable is made out of thousands of strands of steel wire. They are fixed to concrete anchors at each end of the bridge. Most long bridges are suspension bridges. This suspension bridge in the IOSA is called the Golden Gate Bridge.

悬索桥上有一条由结实的钢索悬挂的道路。 电缆由高塔支撑。 每根电缆都是由数千股钢丝组成的。 它们被固定在桥两端的混凝土锚上。 大多数长桥都是悬索桥。 IOSA的这座悬索桥被称为金门大桥。