【正文】 n yet simple appearance of the cablestayed bridge makes it an attractive and distinct landmark. The unique properties of cables, and the structure as a whole, make the design of the bridge a very plex task. For longer spans where winds and temperatures must be considered, the calculations are extremely plex and would be virtually impossible without the aid of puters and puter analysis. The fabrication of cable stay bridges is also relatively difficult. The cable routing and attachments for the girders and towers are plex structures requiring precision fabrication. There are no distinct classifications for cablestayed bridges. However, they can distinguished by the number of spans, number of towers, girder type, number of cables, etc. There are many variations in the number and type of towers, as well as the number and arrangement of cables. Typical towers used are single, double, portal, or even Ashaped towers (illustration 2 amp。 Bridges Girder Bridge A girder bridge is perhaps the most mon and most basic bridge. A log across a creek is an example of a girder bridge in its simplest form. In modern steel girder bridges, the two most mon girders are Ibeam girders and boxgirders. If we look at the cross section of an Ibeam girder we can immediately understand why it is called an Ibeam (illustration 1.) The cross section of the girder takes the shape of the capital letter I. The vertical plate in the middle is known as the web, and the top and bottom plates are referred to as flanges. To explain why the I shape is an efficient shape for a girder is a long and difficult task so we won39。橋的大部分重量和車(chē)輛荷載都被纜索承擔(dān)。橋的兩端通過(guò)放置大型錨固設(shè)備或是重物用以固定纜繩。乍一看 ,這和懸浮的斜拉橋可能看起來(lái)很相似 ,但他們有很大的不同。 斜拉橋沒(méi)有明顯的分類(lèi)。 對(duì)于跨度較大的斜拉橋，必須做出仔細(xì)研究來(lái)確保纜繩和橋梁在風(fēng)力作用下的穩(wěn)定情況。因此三鉸拱很少使用。因此基礎(chǔ)會(huì)承受大量的荷載（水平，垂直，彎曲力），因此無(wú)鉸拱只能在地面基礎(chǔ)十分穩(wěn)定的情況下修建。拱橋可以成為更美橋型之一。 V 型剛構(gòu)橋可以有效地利用基礎(chǔ)。 剛架橋 剛構(gòu)橋梁有時(shí)也被稱(chēng)為框架結(jié)構(gòu)的橋梁。對(duì)于跨度較大的桁架橋，垂直桁架可以提供額外的力（見(jiàn)插圖 2）。然而，一旦組裝的桁架占用較大的空間，以復(fù)雜的結(jié)構(gòu)形成，就會(huì)分散司機(jī)的注意力。 箱梁結(jié)構(gòu)更穩(wěn)定可以跨越更長(zhǎng)的距離且經(jīng)常用于大跨徑橋梁，而使用 I 型梁就不會(huì)有足夠的強(qiáng)度和穩(wěn)定性。 但是在某些情況下，兩個(gè)以上的肋板就會(huì)形成存在剪力滯現(xiàn)象的多室箱梁。一根木頭跨越小河是典型梁橋的一種最簡(jiǎn)單的實(shí)例。要解釋 I 型梁為什么是一種有效的截面型式是一項(xiàng)長(zhǎng)期而艱巨的任務(wù)，因此在本篇文章中我們就不做解釋了。但是，如果梁橋有任何形式的彎曲，梁就會(huì)受扭，也就是眾所周知的扭矩。 因此 ,在大多數(shù)情況下 ,所有梁桁架橋是直的。最具代表性的包括華倫桁架，普拉特桁架以及豪威桁架。 豪威桁架（見(jiàn)插圖 4）是普拉特桁架相反的結(jié)構(gòu)。橋墩和主梁的連接處制作困難，需要計(jì)算準(zhǔn)確且注重細(xì)節(jié)。不像簡(jiǎn)支梁橋，拱橋非常適合用石材建造。 就像桁架橋一樣，道路可能越過(guò)（見(jiàn)插圖 1）或者通過(guò)拱（見(jiàn)插圖 4）或者在某種情況下，兩者都有（見(jiàn)插圖 3）。 三鉸拱（見(jiàn)插圖 3）增加了一個(gè)鉸鏈在拱的頂部。 鋼纜繩非常強(qiáng)韌有彈性。較大跨度的斜拉橋，風(fēng)力和溫度的影響必須考慮，這個(gè)計(jì)算是非常復(fù)雜的，不得不借助計(jì)算機(jī)和計(jì)算機(jī)分析。典型的型式有單面、扇形、豎琴型、星型（見(jiàn)插圖4）。今天明石海峽大橋擁有世界最長(zhǎng)的 1991 米的跨度。有些懸索橋不適用錨錠， 纜繩直接連接主梁的兩端。必須采取特殊的措施以確保大橋在強(qiáng)風(fēng)下不晃動(dòng)或是振動(dòng)。 3.) Cable arrangements also vary greatly. Some typical varieties are mono, harp, fan, and star arrangements (illustration 4.) In some cases, only the cables on one side of the tower are attached to the girder, the other side being anchored to a foundation or other counterweight. Suspension Of all the bridge types in use today, the suspension bridge allows for the longest spans. At first glance the suspension and cablestayed bridges may look similar, but they are quite different. Though suspension bridges are leading long span technology today, they are in fact a very old form of bridge. Some primitive examples of suspension bridges use vines and ropes for cables. The development of metals brought the use of linked iron bars and chains. But it was the introduction of steel wire ropes that allowed spans of over 500m to bee a reality. Today the Akashi Kaikyo bridge boasts the world39。這篇 英國(guó)布里斯托爾大學(xué) 對(duì)于 塔科瑪灣海峽大橋 災(zāi)難的優(yōu)秀的網(wǎng)頁(yè)照片和短片會(huì)解釋為什么空氣動(dòng)力穩(wěn)定性如此重要。 因此，不同于普通橋梁依靠墩臺(tái)承重，懸索