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NOVA scienceNOW: Smart Bridges

Program Overview

Stress and structural deterioration can cause a bridge to collapse, sometimes with little warning. Scientists and engineers discuss new technologies designed to provide warning signs related to the stress and wear experienced by bridges.

This NOVA scienceNOW segment:

• describes the 2007 collapse of a bridge in Minneapolis and its deadly consequences—13 people died and more than 100 were seriously injured.

• explains how the bridge's collapse was related to its design, which had no built-in redundancy to provide backup in case a key part or parts failed. The failure of just a single section caused the entire bridge to collapse.

• points out that the tragedy fueled the call for better inspection technologies that can provide early warning signs before a bridge collapses.

• explains how strain-gauge sensors are used to analyze a bridge's internal structure. They can be welded onto critical spots and can detect if a bridge is overly stressed.

• presents the drawbacks of strain-gauge sensors—they provide limited information of just specific points on a bridge, and they don't give warning of an imminent collapse.

• describes another kind of sensor, piezo-electric sensors. They send ultrasonic waves through a bridge. They can be analyzed to help pinpoint structural damage. A series of piezo-electric sensors can be placed at trouble spots to detect cracks and other deterioration.

• introduces a nanotechnology-skin sensor. It is a coating that, when stimulated with an electric current, detects changes in and damage beneath a bridge's surface. It offers the distinct advantage of providing constant monitoring.

• discusses the properties and advantages of nanotechnology skin. It can be sprayed or glued over critical bridge components. And different kinds of skin, which can be layers on top of each other, can detect different types of damage. Using the skin, engineers can generate a map of a bridge's structure and monitor its performance over time.

Taping Rights: Can be used up to one year after the program is taped off the air.