2023-10-26 18:20:02
Pisa does not have a monopoly on leaning towers in Italy. In Bologna, the very photogenic Garisenda Tower worries scientists and the municipality.
A medieval tower built in the 12th century, the Garisenda is a symbol of the city of Bologna. Located right in the city center, it leans at an angle of four degrees, almost like the more famous Pisa. This tower has a habit of moving, but in recent months, the scientists who monitor it have detected “oscillations anormales”, of the “noises”of the “vibrations”and “movements”, more powerful than normal. They are tiny, barely a few millimeters, but they are worrying.
As a result, traffic around Garisenda Tower was severely restricted. This does not mean, however, that there is an immediate risk of collapse. The Undersecretary for Culture rather evokes a danger of elements of the tower detaching. The mayor of Bologna recalls that the Garisenda Tower has always moved slightly. Sometimes it doesn’t mean anything, but in some cases, you have to act.
It is then essential to move the vibrations away from buses and cars so that scientists can “listen” to Garisenda and understand the extent of the problem. Any trace of movement or crack is carefully monitored with acoustic sensors installed to monitor each crack or suspicious noise.
A trick already planned in the past
The Garisenda Tower dates from the 12th century and was already leaning in the 14th century as the ground beneath it sank. For greater safety, part of its top has been cut off. It measured 60 meters high, it is now only 48. This is not the only renovation to which the tower has been entitled. In 2020, steel belts were installed around it to form a sort of protective shell.
Regarding current studies, nothing has yet been done since a report must be presented in a month. The idea being to protect this flagship monument of Bologna as much as possible. One of the solutions mentioned would be to make the square where the Garisenda tower is located pedestrianized to protect it and its neighbor, Asinelli, another taller and less leaning tower.
Rebalancing and completely straightening a tower is extremely rare. When we cannot stabilize an inclination, most of the time, the tower is destroyed. That of Pisa was still able to be straightened by 0.5 degrees with a system of holes drilled deep into the clayey subsoil.
Pisa and Garisenda are not the only ones to be inclined. In St. Moritz, Switzerland, a tower leans more steeply than Pisa and Garisenda. To limit the damage, the bell at its top was removed. Another very emblematic tower is also leaning, that of Big Ben in London. It leans 0.3 degrees, a tilt almost invisible to the naked eye.
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