Why Pisa’s leaning tower hasn’t toppled
THE leaning Tower of Pisa famously slants but has never fallen – despite being in an earthquake zone.
Now scientists have come up with a new angle on why the tower has never toppled.
It seems the same silty earth that causes it to tilt is cushioning it from strong tremors.
The tower, which was constructed in 1173, has survived at least four strong quakes that have hit the region since 1280.
It is all the more mysterious given that the tower looks like it might fall over at any point.
So a 16-strong team of scientists from the University of Bristol and University of Rome conducted an extensive study of the 190ft tall tower. They conclude that its survival is down to a phenomenon known as dynamic soilstructure interaction.
The height of the tower – combined with the softness of the foundation soil – acts as a dampener when tremors hit the area.
It ensures that the tower does not feel the effects of earthquake ground motion. This has been the key to its survival.
Professor George Mylonakis, from the University of Bristol’s department of civil engineering, said: ‘Ironically, the very same soil that caused the leaning instability and brought the tower to the verge of collapse, can be credited for helping it survive these seismic events.’
Results from the study will be formally announced at the 16th European Conference in Earthquake Engineering in Thessaloniki, Greece, next month.
The tower’s foundation – which is around 10ft thick – is considered inadequate for such a tall building. Its construction was not completed until 1371, having been interrupted several times due to political unrest. The delays during the build also allowed underlying soils to settle, adding to the structure’s stability.