堕落紅尘
首先，我们来基本了解一下拱桥的结构形式与受力特点。拱桥在竖向荷载的作用下，在合理的拱轴线的情况下，拱作为受力杆件，表现为主要承受轴向力，弯矩应该是要尽量避免的，这样才能充分发挥拱肋断面作为轴向受力元件的特点，高效率得利用构件截面。既然我们知道了拱是轴向受力构件，那么，在拱的端部，也就是拱脚处，产生了X向，和Y向的反力，所以，拱桥关键的受力问题要解决的是，拱肋自身的强度问题与拱脚处基础承受的水平与竖向力，这里拱桥更多的是体现在水平力上面，也就是拱桥最后其实应该是个推力结构。好了，了解完拱桥的基本受力状况后，我们来了解一下古代拱桥的构造特点，中国古代拱桥更多是上承式拱桥，也就是桥面系与传载结构是在拱圈之上的，也就是所说的拱上建筑，所谓上承式。桥面直接承受荷载，然后传递到下面拱圈之上，最后传递到拱脚处。因为没有查到具体的古人怎么建造拱桥的施工设计方法，所以，我想做这样的推算，就是我只有我上面这些可以通过显而已经经验所总结出来的理论，完全抛弃现代强度理论的知识，来推测一下古人的建造思路。首先，拱肋是受压构件，古代的材料主要是木头与石块（我这里就主要讨论石拱桥了，木拱桥作罢），石头是很好的圬工材料，类似于现在的混凝土，由受压构件从而选择良好的圬工材料，这解释了古人在材料方面选择方面的这一环节。然后，关于提到的拱轴线弧度的问题，我还要先解释一下，拱轴线的选择，在现今主要由，圆弧线，二次抛物线，高次曲线，悬链线等等，这里有个关键问题，问题中提到的，为什么古代拱肋的轴线弧度都比较大，因为弧度大，拱肋的拱的效应，也就是受压的特点才能体现过来，如果拱肋做得过于平坦，那么梁的效应就大大体现出来，弯矩的效应就大大增加，弯矩我们知道，会让拱肋断面上压下拉，圬工材料的软肋就体现出来了，受拉是绝对不利的，在现在，钢材是良好的受拉受压构件，二就算是现代的混凝土，受拉也是很吃力的，所以这就解释了为什么古人选择弧度比较大的拱轴线，也就是出于安全的考虑，当然弧度越大，曲线美也能更多得体现出来。最后我想讨论一下就是关于基础的选择，据我所知，赵州桥的基础是极为良好的，这里涉及到的问题就不是拱桥所单独面对的了，所谓驳岸的冲刷，基础的沉降，赵州桥都控制的极为良好，基础作为拱桥生命线是极为关键的这里补充一个看似不重要的因素，由于力学知识和材料特性的限制，古代拱桥是不可能建造得像现如今一样长的，但是桥作为一个跨越构造，特别上桥作为跨越水面的构造时，通航要求很多时候会成为左右桥梁外形的关键因素，如果细心一下一点就会发现，古代石拱桥，中国南方的话由于水路运输比较发达，通航的要求就显得很明显，拱的线形就会显得非常夸张，完全是为了桥下的船只通过，中国古代北方的话主要是陆路运输，马车等等，所以出现的拱桥的线形就会比较平坦一点。
吃鱼的猫g
赵州桥又称安济桥，坐落在河北省赵县洨河上，横跨洨水南北两岸，因桥体全部用石料建成，俗称“大石桥”。建于隋朝年间公元595年——605年，由著名匠师李春设计建造，距今已有约1500年的历史，是当今世界上现存最早、保存最完整的古代敞肩石拱桥。在漫长的岁月中，虽然经过无数次洪水冲击、风吹雨打、冰雪风霜的侵蚀和8次地震的考验，却安然无恙，巍然挺立在清水河上。赵州桥，桥身长50．82米，宽9．60米，大拱的净跨度长米，拱高米。这座桥的特点是：一、全桥只有一个大拱，长达米，在当时可算是世界上最长的石拱。桥洞不是普通半圆形，而是像一张弓，因而大拱上面的道路没有陡坡，便于车马上下。二、大拱的两肩上，各有两个小拱。这是创造性的设计，不但节约了石料，减轻了桥身的重量，而且在河水暴涨的时候，还可以增加桥洞的过水量，减轻洪水对桥身的冲击。同时，拱上加拱，桥身也更美观。三、大拱由28道拱圈拼成，就像这么多同样形状的弓合龙在一起，作成了一个弧形的桥洞。每道拱圈都能独立支撑上面的重量，一道坏了，其他各道不致受到影响。四、全桥结构匀称，和四周景色配合得十分和谐；桥上的石栏石板也雕刻得古朴美观。唐朝的张鷟说，远望这座桥就像“初月出云，长虹引涧”。赵州桥高度的技术水平和不朽的艺术价值，充分显示出了我国劳动人民的智慧和力量。赵州桥的设计构思和工艺的精巧，不仅在我国古桥是首屈一指，据世界桥梁的考证，像这样的敞肩拱桥，欧洲到19世纪中期才出现，比我国晚了一千二百多年。
ShangHaiWendy
中国石拱桥中最为杰出的代表就是河北赵县的赵州桥，它又名安济桥。而最有权威的关于赞美中国古代建筑者在石拱桥方面的卓越智慧的就是茅以升老先生的《中国石拱桥》，下边是一段节选。为什么我国的石拱桥会有这样光辉的成就呢？首先，在于我国劳动人民的勤劳和智慧。他们制作石料的工艺极其精巧，能把石料切成整块大石碑，又能把石块雕刻成各种形象。在建筑技术上有很多创造，在起重吊装方面更有意想不到的办法。如福建漳州的江东桥，修建于八百年前，有的石梁一块就有二百来吨重，究竟是怎样安装上去的，至今还不完全知道。其次，我国石拱桥的设计有优良传统，建成的桥，用料省，结构巧，强度高。再其次，我国富有建筑用的各种石料，便于就地取材，这也为修造石桥提供了有利条件。两千年来，我国修建了无数的石拱桥。解放后，全国大规模兴建起各种形式的公路桥和铁路桥。其中就有不少石拱桥。1961年，云南省建成可一座世界最长的独拱石桥，名叫“长虹大桥”，石拱长达米。在传统的石拱桥的基础上，我们还造了大量的钢筋混凝土拱桥，其中“双曲拱桥”是我国劳动人民的新创造，是世界上所仅有的。近几年来，全国造了总长二十余万米的这种拱桥，其中最大的一孔，长达150米。我国桥梁事业的飞跃发展，表明了我国社会主义制度的优越性。参考资料：
欢乐空间装饰
Across the development and the implement of the bridge cultural geography course resources of the lakeChinese summaryThe People's Republic of China Ministry of Education establishes and promulgates the implement of 《 the geography course standard( experiment) of the senior high school 》 medium suggestion:" Make use of the geography course resources of the school well, the reasonable development outside of school geography course resources, for abundant geography course contents, open the diverse but valid geography teaching of the exhibition form, strengthen the geography teaching vitality, have the important meaning." Be showed from this to develop actively and the full exploitation" across the bridge culture of the lake" geography course resources, not only can let the student study the geography in the social activities knowledge, geography knowledge study nearby, develop the course resources of the style of travelling of have the place betterly to aggressive meaning of the geography as to it's his geography course resources development be of great benefit, providing the way of thinking and the method that can draw lessons from. The culture is a root of race, a 魂 of culture of the mountain of 萧 accumulates the 淀 deep, have the across of the history of more than 8000 years lake bridge culture, more than 2000 year agos Wu to fight more, the road of the 浙 east Tang's poem starts some etc..Belong to the across of the new stone age culture bridge culture of the lake, the river 姆 the 渡 culture that compares the of 著 want that more than 1000 years be apart from now for more than 8000 years of across the lake of bridge culture contain ancient old Wu more the earth is abundant but brilliant culture, have in the world the earliest shipbuilding culture;Have to make the pottery culture and the long paddy rice cultivation histories consummately;Still have the very advanced Chinese herbal medicine culture and the tea cultures at that the origin nourishment of take the bridge culture of across the lake, develop the geography course resources, be the native generation person of mountain of 萧 , from the angle study of the geography acrosses the lake of the natural environment, the humanities environment of the bridge ruins etc. knowledge, study the cultural cist knowledge and study of ancient relics the culture, scoop out it endows with to save of course resources will open widely the visual field of the geography course resources necessarily, enrich" stock" of the geography course resources. The 践 goes the new course principle, the knowledge and ability target, processes and method target, the emotion attitudes and the value targets that combine the geography course, full the cist that scoop out the bridge culture of across the lake discovers the process, historic relic and keepsakes and long brilliant of culture be the course teaching can make use of of factor and condition, necessarily enrich the means and methods of the increment course teaching, the geography teaching of material and information, promote the teachers and the students' an interaction exchanges, push new course of the implement and the development. Take" across the bridge culture of the lake" as to carry the body, this text is on the foundation that the backlog teaching practices the research, guiding the student to take group as the unit, passing the ability to the collections of the data, analyze with the sorting, open the exhibition the research study, train the student the independence study, cooperate learning and investigate sex study, the 锻炼 and raise the student the analysis the problem, collect and tidy up the data, resolving the ability of the geography problem;Make use of" across the bridge culture of the lake", the aggressive development teaching case example, make use of a teaching method of case, build the student and text originally, student and student, students and teacher, teachers and text originally, study with life, of the classroom and society hand over with each other terrace, let geography's study more vivid, concrete, develop the thinking ability, analytical skill of the study, promote the student's geography cultivated manners and humanities state of minds;Set up the elective actively, lead the student to walk into" across the bridge culture of the lake", carry on the on-the-spot investigation, provide various teaching modes and path of the new course teaching, explore the student's geography study interest, spacious their cultural visual field, better understanding home town, have a passion for the home town and concern the home love" house", then can love" country" betterly. This text mainly has the four-part cent to constitute:The first part is talk about a put forward of background, meaning and related research say the 评 ;The second part is to across the lake cultural overview;The third part is the course resources that the bridge culture that acrosses the lake endows with to save;The four-part cent is the development and the implement of the bridge course resources that acrosses the lake. Keyword: Across the lake bridge culture;Geography course;The geography course resources, development make use of
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