Today I learned,
The Eiffel Tower was only designed to last for 20 years
by Discovery News:
Arguably the most widely recognized structure in the world, the Eiffel Tower was designed to stand for only 20 years — and some predicted it would collapse long before then. Even as it was being built for the 1889 Universal Exhibition, a professor of mathematics sagely calculated that when the tower was two-thirds complete, its legs would buckle and the whole thing would come tumbling down, crushing workers and houses alike.
Today, the Eiffel Tower is not only standing but remains in rude health, testifying to the soundness of Gustave Eiffel’s design and the strength of “puddle iron,” the hand-made wrought iron of the late 19th century, say engineers.
Specialists at the Technical Centre for Mechanical Industries, or CETIM, have put together a high-powered computer model based on the 18,000 pieces that comprise the world’s greatest iron edifice and the emblem of Paris. SETE commissioned the model in 2008 to fine tune its maintenance program — to get a better idea of the 324-meter (1,063-feet) tower’s weak and strong points as important projects are carried out.
In 2011, the tower will get its 19th coat of paint, and next year sees an overhaul of structures on its first floor. The tower itself weighs around 9,369 tons, to which some 3,306 tons (restaurants, lifts, TV antenna and so on) have been added.
Computer simulation has become standard practice for modern-built buildings, such as the Petronas towers in Kuala Lumpur and the Burj Khalifa in Dubai, and for bridges, such as the Millau viaduct in southwestern France. But creating the model for the Eiffel Tower presented a technical challenge of a completely new kind. One thing was that the realization that its materials — puddle iron (iron that is super-heated, beaten by hand and then folded over) and rivets — perform quite differently from modern-day steel, concrete and bolts.
Materials scientists carried out mechanical and chemical tests on samples of puddle iron to assess its resilience, and stress engineers revisited Eiffel’s own drawings to calculate how the tower would perform under load from the natural elements. Outwardly simple, the geometry of the tower itself posed some mighty number-crunching problems.
The program had to take into account a range of weather conditions on a latticework of 18,000 metal pieces and the tower’s additions, calculating the load vertically, horizontally and in 3D: in all, the model has an astonishing million variables.
The tower has shrunk by some 13 centimeters (5.5 inches) over the past 120 years because it has settled under its own weight, says Roussin.
It amazes me how structures like the Eiffel Tower have been able to withstand for centuries.
Today, humans rely on computers in order to build structures but centuries ago all they had were math formulas. And yet, the Tower still stands.