n
n
n
Onnthis date in 1964, the Italian government made an announcement:nplease, world of engineers and architects, help us prevent thenLeaning Tower of Pisa from collapsing.
Onnthis date in 1964, the Italian government made an announcement:nplease, world of engineers and architects, help us prevent thenLeaning Tower of Pisa from collapsing.n
n
n
nAlmostnas soon as construction started on this grand bell tower, way back inn1173, the building started leaning one direction. When only threenfloors had been built, construction stopped for almost a century.nWhen work resumed, the chief engineer decided to compensate for thenvisible lean by making the new stories slightly taller on the shortnside. In 1278, workers reached the top of the seventh floor—and thentower was leaning nearly three feet! Construction stopped again.
n
n
n
nInn1360, builders decided to finish off the tower with an eighth andnfinal story. Again, a cheat was used to counteract the lean—thisntime, the bell chamber was built with a slight slant in relation tonthe rest of the tower. By 1370, the structure was declared finishednand declared an architectural wonder. People came from all over tonadmire it. Look at the six external arcades! The 200 columns! Thenvery distinct lean!
n
n
n
 |
| One reason people want to visit the tower is to take advantage of this photo op! |
n
nThentower leaned just a little more each and every year—although ofncourse that only made people even more interested in seeing it! n
n
n
n
nInnthe 1500s, the top was 12 feet south of the base. In the 1800s, annarchitect was ordered to excavate the part of the base that had sunkninto the ground—and water came up out of the ground, and the towernlurched another few inches to the south. In the 1900s, Mussolininordered engineers to pour concrete into the foundation to reverse thentilt. But the tower leaned even more inches southward!
n
n
n
nRecentlynscientists have discovered that the tower was built over the remainsnof an ancient river estuary, on ground filled with water and siltynsand. No wonder the building has been sinking!
n
n
n
nAfternthe 1964 call for help, two different attempts to stabilize thenbuilding resulted in even greater leaning. Finally, in 1990, thenItalian government closed the building to visitors out of safetynconcerns. Plastic-coated steel tendons were built around the tower, anconcrete foundation with counterweights was created on the north sidenof the tower. These measures helped reverse a bit of the learn butnwere a bit “unsightly.”
n
n
n
 |
| Lead counterweights, 1998. This is what I saw when I visited Pisa. |
n
n
n
 |
| This 2004 photo shows no cables– when I went, there were lots of cables!–and shows people at the top of the tower–which wasn’t allowed when I was there. |
n
n In 1999, engineers began to very slowlynextract soil under the north side of the tower—just a gallon ofnsoil a day—using massive steel cables to stabilize the tower duringnthe process. By the end of 2001, 18 inches of lean was reversed, andnthe tower was reopened to the public.
n
n
n
nOfncourse, the only time I visited the Leaning Tower of Pisa was duringnthe 11 years it was closed! Rats!
n
n
n
n
n
n
n
nAlsonon this date:
n
n
n
n
n
nScience celebrations
n
n
n
n
n
nAuthor Henry Wadsworth Longfellow’s birthday
n
n
n
n
n
nAuthor John Steinbeck’s birthday
n
n
