Concern about the leaning Garisenda Tower in Bologna
Orange fences and fluttering tape block the way to one of Bologna's most important symbols and thus shape the image of the historic city center. An unusual sight, but the northern Italian city fears for one of its landmarks: The famous leaning Garisenda Tower is causing increasing concern for the city administration and experts due to new cracks in the masonry and recently discovered swaying.
The experts, who have been monitoring the tower and its movements for years, even write of the "highest alert level" in an early scientific report to the mayor. The fear of the stone giant collapsing has returned.
The two leaning towers Garisenda and Asinelli are among the most important sights in Bologna. They stand in the central Piazza di Porta Ravegnana and dominate the cityscape. For centuries, people have been fascinated by the twin towers, which look like skyscrapers when viewed from above from the narrow city center. Even the Italian national poet Dante Alighieri wrote about the Garisenda Tower in his Divine Comedy and later mentioned it again in a sonnet.
There are also leaning towers in Germany
Of the two twin towers, the smaller Garisenda Tower in particular is noticeably leaning: it is 48 meters high and has an inclination of 3.20 meters and almost four degrees. The Torre della Garisenda was built on behalf of a wealthy family in 1109 and was originally 60 meters high, but had to be lowered in the 14th century due to initial construction errors.
Experts cite the foundations and groundwater subsidence as the reasons for the tower's inclination. When the Garisenda Tower was built, Bologna in the 12th century was characterized by several such "skyscrapers". Influential and wealthy families built around 150 family towers and tried to build their own higher than the previous one. Next to the Garisenda Tower is the Asinelli Tower, which is twice as high and currently stands stable.
Leaning towers are nothing unusual worldwide. The classic among the leaning towers stands in Pisa with an angle of inclination of almost four degrees; it is a tad more inclined than the Garisenda Tower. Shortly after construction began in the 12th century, there were already problems with the statics of the free-standing bell tower because the ground under the foundations was sinking away. Many rescue attempts have prevented the tower from falling over to this day.
There are also several leaning towers in Germany. Measured by the angle of inclination, the former fortified tower in Gau-Weinheim near Mainz in Rhineland-Palatinate is currently at the top of the official list. The Record Institute for Germany (RID) confirmed an inclination angle of 5.43 degrees in September 2022. The tower thus topped the approximately 27-metre-high church tower of Suurhusen in East Frisia. This has an inclination angle of 5.19 degrees.
Particularly unusual fluctuations
A scientific and technical committee has been monitoring the two leaning towers in Bologna since 2018 - in particular, the cracks in the masonry and the swaying and vibrations that cannot be seen with the naked eye are being investigated.
In October, the experts noticed particularly unusual swaying. The city council of Bologna therefore closed the square around the two towers to visitors. According to the city, the square will remain closed for several years. Buses were also rerouted due to concerns that the vibrations on the road could deepen cracks. The aim now is to examine how the factors that lead to cracks can be reduced. An iron structure has already been fixed around the masonry.
However, this is not going fast enough for the experts on the committee convened especially for the Garisenda Tower. The dangerous situation is severe, but also unpredictable, said architect Amedeo Bellini to the newspaper "La Repubblica". "We can't say whether nothing will happen to the tower or whether there will be a partial or sudden collapse." And if this were to happen, it is above all impossible to know "whether it will happen tomorrow or in a month's time", said Bellini. The city should take measures to make it safe.
The quality of the masonry is worse than ever before due to various influences, said Sergio Lagomarsino, professor of structural engineering. Therefore, there is no need to panic, but absolute caution is required.
Source: www.dpa.com
