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  3. When an eight-lane steel-truss-arch bridge across the Mississippi River in Minneapolis collapsed during the evening rush hour on

When an eight-lane steel-truss-arch bridge across the Mississippi River in Minneapolis collapsed during the evening rush hour on

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问题    When an eight-lane steel-truss-arch bridge across the Mississippi River in Minneapolis collapsed during the evening rush hour on August 1st 2007, 13 people were killed and 145 were injured. There had been no warning. The bridge was 40 years old but had a life expectancy of 50 years. The central span suddenly gave way after the gusset plates that connected the steel beams buckled and fractured, dropping the bridge into the river.
  【R6】______The St. Anthony Falls bridge, which opened on September 18th, 2008 and replaces the collapsed structure, should do just that. It has an embedded early-warning system made of hundreds of sensors. They include wire and fibre-optic strain and displacement gauges, accelerometers, potentiometers and corrosion sensors that have been built into the span to monitor it for structural weaknesses, such as corroded concrete and overly strained joints.
  【R7】______Another example is the six-lane Charilaos Trikoupis bridge in Greece, which spans the Gulf of Corinth, linking the town of Rio on the Peloponnese peninsula to Antirrio on the mainland. This 3km-long bridge, which was opened in 2004, has roughly 300 sensors that alert its operators if an earthquake or high winds warrant it being shut to traffic, as well as monitoring its overall health. These sensors have already detected some abnormal vibrations in the cables holding the bridge. 【R8】______
   The next generation of sensors to monitor bridge health will be even more sophisticated. For one thing, they will be wireless, which will make installing them a lot cheaper. 【R9】______
   Dr Lynch is the chief researcher on a project intended to help design the next generation of monitoring systems for bridges. He and his colleagues are also looking at how to make a cement-based sensing skin that can detect excessive strain in bridges. Individual sensors, says Dr Lynch, are not ideal because the initial cracks in a bridge may not occur at the point the sensor is placed.【R10】______He is also exploring a paint-like substance made of carbon nanotubes that can be painted onto bridges to detect corrosion and cracks. Since carbon nanotubes conduct electricity, sending a current through the paint would help engineers to detect structural weakness through changes in the paint’s electrical properties.
   A. The new Minneapolis bridge joins a handful of "smart" bridges that have built-in sensors to monitor their health.
   B. The kilometers of wire needed to connect sensors to central computers can add significantly to the system’s cost, according to Jerome Lynch of the University of Michigan, Ann Arbor.
   C. By 2025 all bridges in America will have been equipped with this advanced technology.
   D. A continuous skin would solve this problem.
   E. In the wake of the catastrophe, there were calls to harness technology to avoid similar mishaps.
   F. Engineers then installed additional weights as dampeners.
【R7】
选项
答案A
解析 本题的答题要点是把握第三段的要点：希腊的一座桥梁也采用了相似的避险设计。选项A中的“a handful of‘smart’bridges”与下句中的“Another example”相呼应。
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