Recommended for: Grades 6-12
Resource: The Leaning Tower: Where It Stands Today
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According to John Burland, the engineer in charge of the most recent effort to stabilize the tower, "The Tower of Pisa is notorious for springing surprises on those who try and stabilize it." However, stabilizing the tower was a risk that government officials and engineers had to take in order to save it. In this interview from the NOVA Web site, Burland explains the technique his team used to prevent the Leaning Tower of Pisa from toppling.
Loading reviews...Teachers' Domain, The Leaning Tower: Where It Stands Today, published February 20, 2004, retrieved on ,
http://www.teachersdomain.org/resource/phy03.sci.engin.design.leaningtower/
- Background Essay
- Questions for Discussion
- Standards
Print Background EssayLong before its closure, engineers recognized that something must be done to prevent the tower's collapse. Over several centuries, dozens of attempts were made to stabilize it. Unfortunately, until recently, none of these interventions had any positive effect on the tower's stability -- and some imposed greater risks on the structure than doing nothing at all.
By the late 1990s, according to some mathematical models, the tower was leaning so much that it should already have fallen! Something had to be done. In 1999, engineers began removing soil from underneath the tower's north side in an effort to correct its southward lean. Tests and experience with other towers suggested that extracting soil from the high side of the foundation would cause the structure to settle on that side, moving the entire tower back toward a more vertical stance.
Indeed, in the first few months, the soil extraction technique caused the tower to move to the north about 2.5 cm (one inch). In the ensuing months, by extracting soil at a higher rate, engineers moved the tower another 42.5 cm (17 inches).
By June of 2001, engineers declared the stabilization project complete, even though the tower continued to lean about 4 meters (13 feet) past vertical at its top. Presumably, they could have reversed the lean entirely. Instead, they reduced the lean by just 10 percent, an amount sufficient to stabilize the tower for several hundred years without taking away the building's historic charm. The still-leaning Tower of Pisa was reopened to the public in December 2001.
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See Also:
K-12 Subject:
Construction Technologies
Gravity
History and Impact of Technology
Source: NOVA: "Fall of the Leaning Tower"
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