When the Golden Gate Bridge began construction in San Francisco, some people weren’t sure that such a massive undertaking was even possible. Now the modern suspension bridge is such a familiar and trusted sight that no one questions the long-waiting plans for construction of the Strait of Messina Bridge, which is meant to join mainland Italy to Sicily. It will be the world’s largest suspension bridge, at 10,800 feet, over 60 percent longer than its nearest competitor.
Suspension bridges in general are long-familiar parts of human technology and engineering. The ancient Incas had over 200 such bridges by the 16th century, some which reached150 feet over gorges and were made out of fiber consisting of cotton, grasses, sapling, and wool from llamas and alpacas. But it is only with the advent of modern technology and modern materials that suspension bridges have the limitless potential that makes the Strait of Messina Bridge seem feasible.
The drastic improvements are evident in design, construction, and maintenance. As designs become more ambitious, it is necessary bridges become more aerodynamic to reduce drag from wind, and the pylons at the base of bridges become increasingly flexible to absorb seismic activity without any damage to the structure.
Start of the Modern Era
The mass production of steel starting in the mid-1800s did much to make more ambitious bridges possible, and it led to more bridges being constructed worldwide in the last 150 years than in the 4,000 years prior. Steel has a tremendous combination of compressive and tensile strength. It is able to not only support the weight of a heavy structure, but also to make up highly-stressed cables that compensate for sag on very long bridges.
It is not just the raw materials of the modern era that make ultra-long suspension bridges possible, but it is also the technology that makes those materials particularly usable. That includes the industrial processes that allow for the manufacturing of wound cables, reinforced girders, and so on. It also includes the heavy machinery, load cell technology, and similar instrumentation that allows engineers and builders to determine the exact forces involved at every level so as to be certain of flawless construction and prevent the catastrophic failure that plagued some early bridge designs.
Keeping it Together
The same technological advantages apply to maintenance of bridges. Load cells and diagnostic tools let structural engineers identify faults during routine inspections that they may not have been able to recognize without technological assistance. Advantages like that help to make modern, ambitious suspension bridges not only more feasible in terms of design, but also more cost-effective, with small scale repairs and upgrades that eliminate the need for more expensive maintenance later on.
For all these reasons, Italian engineers see fit to push forward with plans for the world’s longest suspension bridge, based on designs completed in 1994. The public evidently has such natural confidence in this sort of project that they can easily accept that the six billion euro price tag will be justified by the economic impact of the structure and the fact that today’s engineering industries can achieve such great feats as the Strait of Messina Bridge without failure, costly flaw, or unintended consequence.
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