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The World¡¯s Longest Bridge
Rumor has it that a legendary six¡ªheaded monster lurks in the deep waters of the Tyrrhenian Sea between Italy and the island of Sicily£®¡ª¡ª(1)¡ª¡ªWhen completed in 2010£¬the world¡¯s longest bridge will weigh nearly 300£¬000 tons¡ªequivalent to the iceberg that sank the Titanic¡ªand stretch 5 kilometers long£®¡°That¡¯s nearly 50 percent longer than any other bridge ever built£¬¡±says structural engineer Shane Rixon£®
¡ª¡ª(2) ¡ª¡ªThey¡¯re suspension bridges£¬massive structures built to span vast water channels or gorges£®A suspension bridge needs just two towers to shoulder the structure¡¯s mammoth weight£¬thanks to hefty supporting cables slung between the towers and anchored firmly in deep pools of cement at each end of the bridge£®The Messina Strait Bridge will have two 54£¬100-ton towers£¬which will support most of the bridge¡¯s load£®The beefy cables of the bridge£®each 1.2 meter in diameter, will hold up the longest and widest bridge deck ever built£®
When construction begins on the Messina Strait Bridge in 2005£¬the first job will be to erect two 370 meter-tall steel towers£®¡ª¡ª(3)¡ª¡ªGetting these cables up will be something£®It¡¯s not just their length¡ªtotally 5.3 kilometers¡ªbut their weight£® ¡ª¡ª(4)¡ª¡ª
After lowering vertical¡°suspender¡±cables from the main cables£®builders will erect a 60 meter-wide 54.630-ton steel roadway, or deck¡ª¡ªwide enough to accommodate 12 lanes of traffic£®The deck¡¯s weight will pull down on the cables with a force of 70£¬500 tons£®In return£¬the cables yank up against their firmly rooted anchors with a force of 1 39¡£000 tons¡ªequivalent to the weight of about 100£¬000 cars£®Those anchors are essential£®¡ª¡ª(5)¡ª¡ª
Á·Ï°£º
A Some environmentalists are against the project on biological grounds£®
B What do the world¡¯s longest bridges have in common?
C If true£¬one day you might spy the beast while zipping(ºôÐ¥¶ø¹ý)across the Messina Strait Bridge£®
D They¡¯re what will keep the bridge from going anywhere£®
E The second job will be to pull two sets of steel cables across the strait£¬each set being a bundle of 44,352 individual steel wires£®
F They will tip up the scales at 166,500 tons¡ªmore than half the bridge¡¯s total mass£®