交通专业英语-L8.ppt

paragraph 14 Electronic computers are playing an ever—increasing role in assisting bridge designers in the analysis of forces． 在受力分析方面，计算机对桥梁设计者的帮助日益显著。 The use of precise model testing，particularly for studying the dynamic behavior of bridges，also helps designers． 精确的模型试验，对于设计者也是有所帮助的，尤其是研究桥梁的动力特性时。 paragraph 14 A scaled—down model of the bridge is constructed，and various gauges to measure strains，accelerations，and deformations are placed on the model． 按比例制作一个小桥梁模型，测量该模型的应变，加速度，变形。 The model bridge is then subjected to various scaled—down loads or dynamic conditions to find out what will happen． 为研究可能发生的情况，对桥梁模型按比例施加荷载和动力条件。 paragraph 14 Wind tunnel tests may also be made to ensure that nothing like the Tacoma Narrows Bridge failure can occur． 也要进行风洞试验以确保不会出现类似塔科马海峡大桥那样失效的情况。 With modern technological aids，there is much less chance of bridge failure than in the past． 得益于现代技术的帮助，现代桥梁很少会像过去那样失效。 paragraph 15 Construction the foundations．Construction starts with the foundations，which may cost almost as much as the superstructure． 基础工程的建设。施工建设始于基础，基础和上部结构的造价基本一样。 Foundations built in water usually present the greatest difficulties． 基础工程如在水中作业则通常困难重重。 paragraph 15 One of the older methods，which is still used in shallow waters，is to erect cofferdams similar to the ring of closely spaced piles that the Romans used． 在浅水地区，依然可以采用建造围堰这种比较古老的办法，它类似于罗马人采用过的环形布置的小间距桩。 paragraph 16 For constructing foundations in deep water，caissons have long been used． 在深水中建造基础，一直采用沉箱。 The caisson，which is a huge box closed on all sides except the bottom，is lowered onto the river bed． 沉箱是一个除了底部以外四周密闭的巨大的箱子，它置于河床底下 。 paragraph 16 Workers inside the caisson，which is filled with compressed air to keep out the water，dig deeper and deeper，and the caisson sinks as the digging proceeds． 工人们在为挡水而充满压缩空气的沉箱里，越挖越深，沉箱随着开挖的进行而下沉。 When a suitable depth is reached，the caisson is filled with concrete and becomes part of the foundation itself． 当它沉到合适深度，就注满混凝土使之与基础联成一体。 paragraph