Brilliant Bridges

Brilliant bridges

了不起的桥梁

Bridging the Gap Bridges carry people and vehicles across rivers, roads, railways and valleys. They make it easier to travel from one place to another.

跨越阻隔 桥梁可以载着人和车辆跨越河流、公路、铁路还有山谷。 有了桥梁，人们往返不同地方就更方便啦。

Bridges come in different shapes and sizes. Before a bridge is built, engineers think about what type of gap it's going to cross and what it will be carrying – cars, trains, people or water. Then they work out the best type of bridge for the job and the best materials to use. The Millor Viaduct in France carries a motorway across a wide valley. It's one of the tallest bridges in the world.

桥梁的形状和大小各不相同。 在建桥之前，工程师要先考虑这座桥要跨越的是什么类型的阻隔 还要考虑桥要承载的是什么——汽车、火车、行人，或是输水管道。 然后他们会选出最适合的桥梁类型，还有最合适的建筑材料。 法国的米约高架桥承载着高速公路横穿宽阔的山谷。 它是全世界最高的桥梁之一。

Arch bridges The very first bridges were built thousands of years ago. They were fallen trees or stone slabs laid across streams. The bridge takes the weight of the people crossing over. The ground carries the weight of the traffic and the bridge.

拱桥 最早的桥梁出现在几千年前。 就是架在小溪上的倒树或是石板。 桥身承担过桥行人的重量。 地面再承载交通和桥梁的总重量。

These bridges were good for crossing small gaps, but they broke if the traffic was too heavy or the bridge was too long. So, about 3 ,500 years ago, the arch bridge was invented to cross wider gaps. The bricks in the arch are shaped to squeeze together and support each other. The arch moves the weight of the traffic and the bridge down to the ground. The ground carries the weight of the traffic and the bridge.

这类桥适合跨越小的缺口，但如果通行的东西太重，或是桥身太长，桥就会断裂。 所以大约3500年前，人们发明了拱桥，用来跨越更宽的缺口。 拱圈里的砖块形状特殊，能互相挤压、彼此支撑。 拱圈会把交通和桥梁的重量传导到地面。 地面再承载交通和桥梁的总重量。

If a stone arch is too wide, it becomes too heavy and falls down. To cross bigger gaps, engineers built bridges with a set of smaller arches. This spread the weight evenly across the structure. Now, they could build much longer bridges. Did you know? The Pont du Gard aqueduct was built in France over 2000 years ago. It supplied the city of Nîmes with 200 million litres of water every day.

如果石拱桥的拱圈太宽，桥身就会过重，容易坍塌。 为了跨越更大的缺口，工程师会建造有多个小拱圈的桥。 这样能把重量均匀分散到整个桥体结构上。 这样一来，人们就能建造长得多的桥梁啦。 你知道吗？ 法国的加尔桥水道是2000多年前建造的。 它每天能给尼姆市输送2亿升的水。