September 1960
Now 17 feet out of line, the 8OO-year-old wonder may collapse before long
Ways to save a sagging tower: jack it up, shore it up, gird it 'round with iron bands - then cross your fingers
By Joan Steen
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September 1960 Now 17 feet out of line, the 8OO-year-old wonder may collapse before long Ways to save a sagging tower: jack it up, shore it up, gird it 'round with iron bands - then cross your fingers By Joan Steen |
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PISA'S famous tower will fall - unless someone quickly thinks of a way to save it. Come up
with a workable plan that the experts haven't thought of and the Italian government may well lavish upon you undying thanks, honorary Pisan citizenship, and fistfuls of lire.
It won't be easy. The 179-foot tower is already 17 feet out of kilter and shows alarming signs of galloping to its death. The lean has been accel- erating. Once 0.04 inch a year, it's now up to 0.06 inch. How much longer this can go on before the tower reaches the tilt of no return authorities shudder to predict. Some think it won't last another generation.
Shhhh! Meanwhile scientists quietly bedside-watch the decline of their patient. They've installed seismographs and an inclinometer inside the tower to record the changes. They've silenced the tower bells and banished cars and motor scooters from the surrounding plaza, lest noisy vibrations set up fatal shiverings: Years ago the scientists operated. To shore up the sandy foundation blamed for the tower's troubles, they drained rain water from the low side and injected 93 tons of concrete. This seemed to work for a while. Then in World War II a stray shell fired dur- ing the Battle of the Arno damaged part of the tower's upper level. New shakes set in and started the tower's slow-mo- tion leaning again. |
 FAMOUS BELL TOWER at Pisa, begun in 1174, was finished two centuries later. Now its bells no longer toll the hours: Their vibrations might be fatal. |
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Early inclinations. The 800-year-old tower began life with a lean. Bonanno Pisano, who designed it and began construction in 1174, was more artist than engineer. When the first few floors showed leaning tendencies, he decided to fix things by making the next few tend a little in the opposite direction. No one, thought Bonanno, would ever know of his improvisation. But the city fathers did, and fired Bonanno. Work was picked up a century later by a hunchback, Giovanni di Simone. By this time the tower was 10 inches out of plumb, so Giovanni added his three stories at a compensating angle. He quit under pressure of critics who said they could do without a hunchback tower. The finishing touches waited another century to be put on, this time by an unknown architect. Presumably neither hunchback nor near-sighted, he nonetheless didn't match the diameter of the rest of the building when he added the smaller belfry. |
CROOKED TOWER'S CROOKED SPINE shows up in the cutaway drawing. Hold a straightedge against the central axis. Slight jogs in the line appear at the three-story and belfry levels. |
Falling bodies.That same belfry attracted Galileo two centuries later. In 1589 he climbed the winding staircase to the top to test his theories on the velocities of free-falling objects. He dropped differently weighted balls over the side.
That might be reason enough for the tower's fame had it not already been a tourist favorite. The tower's tipsy beauty has been the city's chief drawing card for centuries, although other Pisan buildings are known to show a certain lack of plumbness, too (proof possibly that the lean wasn't intentional, as some his- torians had thought). So stubbornly proud are some of Pisa's old-timers that they refuse to believe the tower can fall. Legend helps. Some mention an earthquake in 1846 when, according to folklore, the tower touched ground and bounced up again. Others point to favorable winds. The tower leans into prevailing Mediterranean zephyrs, they say, and is buoyed up. But the Government Commission for Vigilance for the Stability of the Bell Tower of Pisa is worried. So far they've considered a number of schemes. |
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An Auxillary tower. The University of Pisa recommends building a temporary steel tower. This would stand next to the to old one and girdle it with iron bands while workmen erected a concrete column through the old tower's center. The steel tower would then be removed.
"Cebertzation." A Polish professor, Romuald Cebertowicz, has an electro- chemical scheme he calls electro-osmosis. It's a means of petrifying a watery foundation through the action of chemical salts. The salts are spread by electrodes acting as pumps ( cathode sucking and anode pressing) .The reactions produce chemicals that solidify the ground and attach it to the building foundation. The technique, dubbed "cebertization" by the professor's colleagues, is being tried in Venice where crumbling pile foundations have been threatening many old palaces on the Grand Canal with watery graves. |
REINFORCED FOUNDATION was not strong to enough to resist the effects of Pisa's marshy soil. . |
 SOARING TO THE TOP of the 179.foot tower are the struts that support an inclinometer. Hardy tourists ( Galileo was one) can make the climb up 293 steps of circular staircase. |
 INCLINOMETER, installed at the. base of the tower, periodically records the lean, Seismographs, also Installed insIde, make round-the- clock readings of the tower's every tremor. |
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Jack it up! A British engineer, Fordham Pryke, has suggested jacking up the 14,500-ton tower to a safer lean of 9-1/2 feet, then putting in a new foundation. While the government weighs the pros and cons of these plans, it has definitely vetoed others. The Texan tourist's, for example. He was all for removing the tower, stone by stone, and setting it up on his nice, solid, dry ranch.
Article and September 1960 Issue from Webmaster Collection  Leaning Tower of Pisa Homepage Leaning Tower of Pisa Information Leaning Tower of Pisa History Leaning Tower of Pisa News Leaning Tower of Pisa Web Links Leaning Tower of Pisa Humor Leaning Tower of Pisa Gallery  E-mail: Gary Feuerstein Page Initiated 20 March 1998 |