In the 20th century， bridge construction technology evolved and was fueled by the Industrial R At the turn of the century， steel bridges were riveted together， not bolted; concrete bridges were cast in place， not precast; and large bridge members were built from lacing bars and smaller sections， not rolled in one Plastic had not yet been Construction techniques such as post-tensioning， slurry walls， soil freezing， and reinforced earth walls had not yet been Surveying was performed mechanically since infrared， optical technology was still 75 years Bridge construction is changing as the new millennium New construction techniques and new materials are There are also new issues facing the bridge building industry relative to the research needs associated with these new techniques and LONG-SPAN BRIDGES Suspension Bridges While suspension bridge building was conducted at a modest pace throughout the 20th century， an unprecedented number of spans of remarkable record lengths were built in the Far East and D Both the Akashi Kaikyo Bridge in Japan and the Great Belt Bridge in Denmark were completed in The Akashi Kaikyo Bridge is the largest suspension bridge in the world， with a span of 1991 m， and the Great Belt Bridge is the second largest， with a span of 1624 While spans lengths have increased nearly fivefold during the course of this century， they may have reached their physical limits with today’s Research will be necessary to develop the new， ultra-high-strength steel wire or carbon fiber wire required to build the longer main suspension cables that will make it possible to increase span lengths to beyond 2000 As we enter the new millennium， rehabilitation and ongoing maintenance of the existing suspension bridges must continue as Recent rehabilitation measures for the main cables and suspension systems of these bridges have uncovered degradation through corrosion and hydrogen Research is needed to determine the remaining useful service life of suspension bridge cables and what measures can be taken to slow or halt the degradation Transportation in the New Millennium 2 Other components of long-span bridges， existing and new， are being revolutionized as technology moves Advances in deck technology are producing stronger， lighter Orthotropic and exodermic decks are becoming increasingly popular on long-span structures as a means of reducing dead Bearings， joint systems， and seismic retrofitting components are becoming increasingly efficient as more large-scale testing facilities are 在20世纪，桥梁施工技术，是由进化而来的 工业革命。随着新世纪的到来，钢桥受到铆接在一起，而不是 螺栓、混凝土桥梁被扔在的地方，不是预制、大型桥梁成员 从系酒吧和小的部分，不卷在一块。塑料尚未 发明了。制作等施工工艺、浆墙、土壤冻结， 加筋土墙尚未怀了孕。测量进行机械 自从红外、光学技术仍然是75年。 大桥建设是新千年开始转变。新建筑 技术和新材料正在浮出水面。也有新的解决面临的桥 建筑行业的相关研究的需要，这些新技术 材料。 大跨度桥梁 悬挂的桥梁 虽然悬索桥建设进行了整个20速度不快 世纪，前所未有的跨越了卓越的长度是建在记录 远东和丹麦。双方在日本明石海峡大桥正式通车，伟大的带桥 在丹麦是在一九九八年完成。这个明石海峡大桥正式通车是世界上最大的悬架 在这个世界上，与桥梁的m，1991年是中国的第二大带桥， 用一段1624)。 虽然已经增加了近5倍长度的跨世纪的过程中， 他们已经达到了他们的物理极限与今天的材料。研究将 必须发展新的、ultra-high-strength钢丝、碳纤维丝要求 建立了悬索，将不再主要可能增加到跨度的长度 超出2000米。 当我们进入新千年、康复和持续的维护现有的 悬索桥必须继续。最近的戒毒措施为主要 电缆悬架系统与这些桥梁发现退化 氢脆腐蚀，。研究还剩下的 寿命悬索桥电缆和什么措施可以减缓或 停止退化的过程。 在新千年的运输 其他组件的大跨度桥梁，现有的和新的，正在发生了革命性的变化 技术的进步。提出了在甲板上技术生产强的，更轻的 甲板。正交各向异性和exodermic牌是大跨度越来越受欢迎 作为一种手段，降低结构自重荷载。轴承、联合系统和抗震能力 越来越多的有效成分是更大规模的测试设备 建造。
