By Isidro de Federico Gordejuela
The Tour de 300 m tres, or the 300-meter tower, was the initial name of the building that is now known as the Eiffel Tower. The engineers who oversaw the tower’s construction, Maurice Koechlina and Mile Nougierto Gustave Eiffel, came up with the name. It alluded to the ambition to create something remarkable, a technological achievement that would break the previous record for height.
The Eiffel Tower, however, rises even higher than it was originally intended to as summer temperatures rise.
A lightweight iron structure
In honor of the 100th anniversary of the French Revolution, the Eiffel Tower was built during the 1889 World’s Fair.
Eiffel used puddled iron, a material he was familiar with and had successfully employed in earlier projects, to construct it. Because of this ferrous material’s great stress tolerance, a huge, lightweight tower that would be safe from horizontal wind pressures might be built.
The tower weighs 7,300 tonnes, which is comparable to the 6,300 tonnes of air it contains. This gives you an indication of how light the tower is.
In addition to serving as a platform for radio broadcasts, the Eiffel Tower was designed to be a prominent observation point. Like the Garabit Viaduct (also designed by Eiffel’s team) and the Forth Bridge in Scotland, which were both built during the same era, the tower itself is a massive triangular lattice construction.
As the material’s temperature rises, all of these structures expand. However, the Eiffel Tower mostly suffers vertical expansion and contraction as a result of temperature variations, in contrast to bridges, which exhibit more complex behavior. The term “thermal expansion” describes this phenomena.
Materials that grow and shrink
The majority of solids, as we know, expand with increasing temperature and shrink with decreasing temperature. This is due to the fact that higher temperatures induce the atoms to become more agitated, which raises the average distance between them.
Engineers must carefully document the growth that various solid types undergo, which varies depending on the type of bond. Due to their stronger connections, ceramics and glasses expand less than metals, which in turn expand less than polymers.
So, how can we calculate how much a solid is moving? The movement of straight elements, which are found in most public works and architecture, where beams and bars are common, is related to three factors: the element’s length, temperature change, and material coefficient of expansion.
A hair s breadth
While metals range from 5 10 to 30 10 (C) and polymers from 50 10 to 300 10 (C), many ceramic materials normally have expansion coefficients between 0.5 10 and 1.5 10 (C). These (perhaps odd-looking) figures show how much a standard-length unit grows when the temperature increases by one degree Celsius.
Metals expand 10 times more than ceramics, while polymers expand roughly ten times more than metals, making them the most expandable materials.
A one-meter-long iron bar expands by 12 10 meters when the temperature rises by one degree because the puddled iron used in the Eiffel Tower and its steel components have a coefficient of about 12 10 (C). That is less than a human hair’s thickness—just a dozen microns.
Does heat affect buildings in any discernible way, then? Yes, provided that we take into account the fact that there are two other factors to take into account: the element’s length and the temperature range in which it is located.
It can be incredibly long. The Garabit Viaduct is 565 meters long, the Forth Bridge is more than 2.5 kilometers long, and the Eiffel Tower is 300 meters high. Larger linear structures are common today, and thermal expansion has an impact on the railroad tracks that many bridges are designed to support.
Analysis of past temperature ranges is also necessary. For over 200 years, Paris has recorded temperatures with summer highs of about 40 degrees Celsius and winter lows of less than -20 degrees. We should also consider the impact of solar radiation, as metals can frequently achieve temperatures of 60 or 70 degrees Celsius when exposed to direct sunshine.
Leaning away from the sun
Let’s do the math now. We’ll calculate how much a straightforward metal bar that is 100 meters long will expand when the temperature changes by 100 degrees Celsius, which is roughly the range that the Eiffel Tower experiences.
It’s an easy computation. When the temperature increases by 100 degrees, a 100-meter bar expands by 0.12 meters, whereas a one-meter bar expands by 0.000012 meters when the temperature increases by one degree. Additionally, a 300-meter bar would grow by 0.36 meters, which is three times as much. 36 centimeters, that is. This is a discernible change.
It is obvious that a tower composed of over 18,000 riveted iron parts oriented in all directions behaves differently than a simple bar. Moreover, one of its sides is always illuminated by the sun. This indicates that one of its faces grows more than the others, giving the tower a little curvature that makes it appear to be tilting away from the sun.
When comparing the Eiffel Tower’s stature on chilly winter days with the hottest summer days, experts have calculated that it truly increases between 12 and 15 centimeters. This implies that the Eiffel Tower is essentially a huge thermometer in addition to being a landmark, a communications tower, and a representation of Paris.
Federico de Isidro Gordejuela teaches architectural constructions at CEU San Pablo University as an adjunct professor.
