- Education and Science
Super Skyscrapers & Mega Bridges Part 4
Plans for the spectacular single-span suspension bridge were conceived 40 years ago. Engineers designed the graceful bridge to withstand a 7.1-magnitude earthquake, stronger than the one that leveled the area in 1908, and winds of 130 miles per hour (216 kilometers per hour). Twelve vehicle lanes (including service and emergency lanes) of traffic and a double-decker railway will allow the passage of 140,000 cars and 200 trains daily.
The bridge was supposed to start construction years ago but has been delayed by Italy's incessant political crises. Since the Italian government seems to eternally swing between hard left and hard right, one side favors the project then loses and election and the other side cancels it, until that side loses the next quick election and the project is reinstated once again. Italians have lost count of how many times this project has received green and red lights. At this time, construction is currently underway, but you'd be hard pressed to see any evidence of that on the site. Nothing but dawdling while money gets sucked away by the local Mafias: Typical Italian project.
The Future in Plastic & Glass
But the construction or lack thereof of the Messina Straits Bridge doesn't mean that innovation in the world of bridge building is collapsing. The real future lies in applying our established engineering principles to structures that will use advanced materials such as fiber-reinforced plastics.
Plastic bridges? Not only plastic bridges, but also glass bridges. The mighty steel and concrete bridges, from the simple arcs over interstate highways to spans that cross rivers, are rusting and crumbling away. More than half of the United States' 600,000 bridges need to be replaced or undergo extensive repairs.
In an effort to develop materials that will last longer than 20 years, the National Science Foundation funded 40 research projects that have inspired several recent bridge-building programs. Scientists have been testing glass bridge material. It looks and feels like ordinary black, hard roadway but is actually made of glass. A glass- and carbon-fiber-reinforced plastic bridge decking is being used to replace some highway bridge decks in Ohio and southern California. Although the plastic bridge material is still three to five times more expensive than concrete, its advantages are many. It's lighter, as a square foot of concrete weighs about 100 pounds, while a square foot of plastic bridge material weighs about 20 pounds. Because it's lighter, more panels can be transported on a single truck. Furthermore, it's more resistant to earthquakes than concrete (always a plus in California). Finally, because the panels can be dropped into place, it takes less than a day for workers to install a new highway bridge surface.
Plastic and glass bridges will grow older than concrete and steel and become smart. Engineers estimate that a glass bridge built now will still be around in 2200, which easily meets the new U.S. highway specifications for a 75-year life span. And researchers are developing methods to incorporate computers into plastic and glass materials to enable bridges to monitor themselves. In the event of damage from accidents or earthquakes, the bridges will be able to alert repair crews.
Plastic and glass even promise a future for new and larger bridges. These new materials definitely open the doors for mega-bridge projects. The fantastic dreams of a span between Morocco and Gibraltar may yet become as practical as the projects of the most down-to-earth bridge builders.