Suspension bridges such as the Golden Gate Bridge and the Brooklyn Bridge are some of the most amazing structures on earth. These aesthetic and technological wonders span rivers, and other obstacles with enough strength to support endless streams of cars and trucks. How do they do it?
All bridges routinely experience compression and tension. The vehicles that press down on a bridge's roadway compress the top half of the road, causing it to shorten like a compressed spring. The bottom half of the road experiences tension, meaning that it elongates like a spring pulled apart.
Suspension bridges are designed to absorb these forces in two ways: dissipation and transference. When a bridge dissipates force it spreads it out over a wider area. Transference involves moving force from a weak area to a stronger area.
Chances are you've seen a suspension bridge and maybe even crossed one. They consist of at least two large towers anchored to the ground, a roadway, and a web of steel cables strung between the towers and from each tower to the anchorages at either end. What's amazing is that the roadway is literally suspended in the air by the cables. It just hangs there as you and thousands of others drive across.
As the roadway hangs from the towers and vehicles move across its surface, the cables transfer the compression forces directly to the two towers, which in turn transfer the brunt of the pressure down into the ground. The cables also absorb much of the tension forces as they stretch under the weight of the roadway and traveling vehicles. Finally, the anchorages absorb some of the force as well.
译文:
建桥
悬索桥，比如金门桥和布鲁克林桥，是地球上的奇妙建筑。这些美学和技术学的奇迹，以强大的力量，跨越江河或其他障碍，为川流不息的汽车流和卡车流提供支持。它们是怎样建成的呢？
所有的桥都不免要经受压力和张力的考验，桥面公路上的车辆会对桥面顶端产生向下的压力，使桥缩短，就像弹簧被压缩；桥面底端会受到张力，使桥变长，就像弹簧被拉长。
悬索桥在设计中用两种方式吸收这些力:分解和转移。
分解意为把力分散到桥上更广的区域；转移意为把力从桥上虚弱的的区域转到较强的区域。
你可能有机会看到悬索桥或从悬索桥上经过。它们都由两个大落地塔，一条公路和系在两塔之间的钢索网组成，两塔上各有系钢网的联系点。
奇妙之处在于桥面公路被钢网悬在空中。它悬在那儿，数以千计的人从上面驶过。
由公路悬在两塔中间，车辆在上面行驶而过，钢网直接把压力传给两塔，两塔再把压力传到地面；钢网还吸收大量的张力，这些张力由公路及其上面的车辆的重力产生。此外，塔上系钢网的系点也吸收一些力。