1、 BridgeBridges that span rivers, valleys such a barrier construction, which provides convenient transportation, so far, most of the bridges are highway bridges or railway bridge. A large number of viaducts built in the 19th century in Europe, aims to maintain its navigation of the ship canal. The sm

2、allest bridge in New York City's Kennedy Airport, it is primarily the aircraft taxiing onto the runway to the service.Humans is similar to the first bridge built in the primitive built in isolated areas. Early human tools and construction techniques as the original, like humans are the most juni

3、or. After they are at least as long as the processing and installation can be completed.In the forest, widely available solid wood and logs, then most likely Hou bridge or by a few logs built side by side, may, in its number of wooden sticks or straw mats on the cover for easy walking.In the tropica

4、l regions of India, Africa, and South America are used to build fiber rattan suspension bridge, the vines are tied to trees on both sides of the river or valley or rock. One or more above the walking cane to be stepped on, others are arranged in Gao Yu a few feet, for hand use. Although rattan rope

5、bridge is usually unstable. But there are many rattan rope bridge with incas built strong and stable enough, to be used for the Spanish soldiers and their horses to pass.In rocky areas, the stone is used to bridge across the river to a small stone pestle as piers spaced, and then use a flat stone ac

6、ross the pier adjacent to the channel linking the two sides completed, most of the stone bridge is this types, called the clap bridge. Now in Dartmoor, England are still visible, but they are built in the Middle Ages or even later.The first step changes the original bridge was considered in ancient

7、China, and then into India. Generally wider than the tree bed, Chinese and Indians in the center of the river into two stumps. In this structure, both ends of the frame with one end of logs on the stump, and tilted slightly upward so that each layer of high than a few feet below it. In order to incr

8、ease stability, both sides each with a bunch of stakes in large and heavy stone anchor; close to the river, in the middle of the river at both ends of the two stakes are connected with beams. In this structure, the natural bridge support bar in the middle of two free pile after a wide span can be ac

9、hieved.As early as 4000 BC in Mesopotamia, and thousands in the year 3000 in Egypt, with stone or sun dried bricks were used to install the overlapping beams. This structure looks like the arch, the lower more stable, is called sudden arch. To suddenly arch into a more straight arch, it needs to fit

10、 the internal structure of the stone smooth. The arch straight arch stronger than sudden, and as early as 500 BC to be used.The stone arch with direct economic and durable, it can rest on the dock by a number of the arch and across the small river. And, it generally will always appear, and its quali

11、ty in any structure to be better than the previous. In ancient China and Rome, which is widely used in the overall stone arch bridge structure. It has been widely used until the 19th century.There are four categories of basic structure can be used as water or obstructions on the bridge: rigid frame

12、bridge, cantilever bridge, arch, and suspension system.The simplest bridge may be just the first use - or just the river bridge. So that it is relatively fixed at both ends of the banks. This rigid frame bridge can form a shaped wooden beams, reinforced concrete beams or more complicated constraints

13、. Just this type of bridge span of the bridge pier was built in the middle can be used or built in the valley support joists, beams connected by a few and then increase the span. Rigid Frame material must be able to bear the stress and tension. Despite its name beam, but in fact the requirements of

14、this dual rod can be used to frame the bridge. Result, the higher part of the beam bending pressure lower than the straight part of the more than half, if he's bearing strength is too weak, it will be into the ring, if the tensile capacity is too weak, he will be destroyed.Cantilever bridge pier

15、s in the use of long-span bridges the middle it is usually not feasible in the bridge structure. For example, in the deep and rapid river flow, or ooze, it may make it difficult to build sufficient depth of bridge pier foundation rock. In this case, just on the bridge structure can be extended with

16、two beams - out of a beam from each shore, and in the two ends of the beam anchorage basis. This simple structure is more rigid frame bridge with static characterization, and each root anchorage of the beam cantilever bridge called such an infrastructure, and perhaps this most simple and familiar ex

17、ample is the cantilever bridge diving board. Cantilever bridge in general, the gap between the cantilever tip is closed, the road to provide a continuous deck. But if the point of this bridge in its closed off, then do not need each other to set the root cantilever support which can maintain stabili

18、ty. Cantilever is usually only the middle of the gap is closed rigid frame bridge. So while filling grain extended cantilever span.Suspension bridge in the absence than in the case of the middle pier cantilever bridge across the greater distance. Suspension of the support system is a continuous flex

19、ible cables by the ends of the anchor, the suspension bridge is the simplest example of high-altitude high-wire acrobat with the circus wire. The original suspension bridge is often a very small few that is tied to steel rails and provide a foothold. At the level of the modern suspension bridge on t

20、he road is suspended by the cable on both sides of the roadway below.Arch is the opposite effect on the suspension bridge, suspension bridge cables in the freedom of those who provide support force where it is from the bridge pillars at both ends of its fixed upward. As different in shape, suspensio

21、n bridge cables tend to stretch all the points of the pillars of the bridge tends to squeeze everywhere. For these reasons, suspension of the cable must be as much as possible to prevent the extension of the bridge material is as hungry to resist compression. Because the arch does not necessarily re

22、quire materials with a tensile strength, so the bridge can be built with brick or stone, brick or stone arch to pass through the characteristics of the pressure together. This material in other basic bridge structure is useless.In the arch, the load on the vertical transmission from the road down un

23、til the arch was destroyed. When the arch was pure pressure to achieve the critical load, they will change the power transmission path. A compression force of the thrust through the node or piers to the ground. This simple and beautiful arch structure of a bridge in one of the basic structure.橋梁

24、60;橋梁是跨越如河流、山谷這樣障礙的一種建筑，從而提供交通便利，到目前為止，大部分橋梁都是公路橋或鐵路橋。大量的高架橋于19世紀(jì)在歐洲建成，目的是保持其運(yùn)河中船舶的航行。最小的一座橋在紐約市的肯尼迪機(jī)場，它主要是把滑行飛機(jī)拖到跑道上服務(wù)的。 人類建成的第一座橋類似于原始人在孤立地帶建成的。早期人類的工具和建筑技術(shù)如同原始人類一樣都是最初級(jí)的。他們只要經(jīng)過最少的加工和安裝即可建成。 在森林里，隨處可得結(jié)實(shí)的木材和圓木，那時(shí)侯的橋極可能是由一根或并排的幾根圓木建成，可能在其上覆一些木枝或草墊以方便行走。 處于熱帶地區(qū)的印度、非洲、和南美洲纖維藤被用來建成懸索橋，這些藤被系在小河或山谷兩邊的樹上或

25、巖石上。一根或更多的藤被踩在上面行走，其它的則排列在膏腴幾英尺的地方，用作手扶用。雖然藤索橋通常不穩(wěn)定。但有很多用incas建成藤索橋有足夠的堅(jiān)固和穩(wěn)定性，被用于西班牙士兵和它們馬匹的通行。 在巖石地區(qū)，石頭被用來建橋，橫跨河流以很小的間距布置石碓作為橋墩，然后用平坦的石頭橫過相鄰的橋墩就建成連接兩岸的通道，大部分的石橋就是這種類型，叫做鼓掌橋。現(xiàn)在在Dartmoor、英格蘭仍然可見，不過它們都建于中世紀(jì)甚至更晚。 原始橋梁的第一步變革被認(rèn)為出現(xiàn)在中國古代，隨后傳入印度。河床一般比樹要寬，中國人和印度人在河流的中央建成兩個(gè)樹樁。在這個(gè)結(jié)構(gòu)的兩端，用圓木的一端架在樹樁上并微微向上傾斜，使其每一層

26、都比它下面的高幾英尺。為了增加穩(wěn)定性，每個(gè)木樁在兩岸都用一堆大而重的石頭錨固；接近河中央，在河中間的兩個(gè)木樁的兩端則用簡支梁連接。在這種結(jié)構(gòu)中，天然支架橋在兩個(gè)自由桿的中間加樁后可達(dá)到很寬的跨度。 早在公元前年的esopotamia和在公元千年的埃及，用石頭或日光烤干的磚被用來安裝重疊的橫梁。這種結(jié)構(gòu)看起來像的拱，下部更平穩(wěn)，被叫做突拱。要使突拱變?yōu)楦钡墓埃枰^的內(nèi)部構(gòu)造適合光滑。這種直拱比突拱更堅(jiān)固，且早在公元前年就被使用。 這種直石拱具有經(jīng)濟(jì)和經(jīng)久耐用，它可以由許多靜止在碼頭上的拱而跨過小的河流。并且，它一般會(huì)經(jīng)常出現(xiàn)，而它的質(zhì)量比先前的任何結(jié)構(gòu)都要好。在中國和羅馬的古代，這種整體石拱被廣泛地用于橋梁結(jié)構(gòu)。它一直被廣泛地使用直到19世紀(jì)。 這里有4類基本結(jié)構(gòu)可以用作水面上的或障礙物上的橋：剛架橋、懸臂橋、拱橋、和懸索橋體系。 剛架橋最簡單也可能是最早使用的-即剛架橋河流。這樣它的兩端固定在相對(duì)的河岸。這種剛架橋可以組成某種形狀的木梁、鋼筋混凝土梁或更復(fù)雜的約束。剛架橋這種類型