500-year-old Leaning Tower of Pisa mystery unveiled by engineers

May 9, 2018, University of Bristol
500-year-old Leaning Tower of Pisa mystery unveiled by engineers
Leaning Tower of Pisa. Credit: University of Bristol

Why has the Leaning Tower of Pisa survived the strong earthquakes that have hit the region since the middle ages? This is a long-standing question a research group of 16 engineers has investigated, including a leading expert in earthquake engineering and soil-structure interaction from the University of Bristol.

Professor George Mylonakis, from Bristol's Department of Civil Engineering, was invited to join a 16-member research team, led by Professor Camillo Nuti at Roma Tre University, to explore this Leaning Tower of Pisa mystery that has puzzled engineers for many years.

Despite leaning precariously at a five-degree angle, leading to an offset at the top of over five metres, the 58-metre tall Tower has managed to survive, undamaged, at least four strong earthquakes that have hit the region since 1280.

Given the vulnerability of the structure, which barely manages to stand vertically, it was expected to sustain serious damage or even collapse because of moderate seismic activity. Surprisingly this hasn't happened, and this has mystified engineers for a long time. After studying available seismological, geotechnical and structural information, the research team concluded that the survival of the Tower can be attributed to a phenomenon known as dynamic soil-structure interaction (DSSI).

The considerable height and stiffness of the Tower combined with the softness of the foundation soil, causes the vibrational characteristics of the structure to be modified substantially, in such a way that the Tower does not resonate with ground motion. This has been the key to its survival. The unique combination of these characteristics gives the Tower of Pisa the world record in DSSI effects.

Professor Mylonakis, Chair in Geotechnics and Soil-Structure Interaction, and Head of Earthquake and Geotechnical Engineering Research Group in the Department of Civil Engineering at the University of Bristol, 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 have been presented to international workshops and will be formally announced at the 16th European Conference in Earthquake Engineering taking place in Thessaloniki, Greece next month [18 to 21 June 2018].

Explore further: Quake test helps set a new standard for building on soft soil

Related Stories

Tilting, sinking San Francisco high-rise raises alarm

October 24, 2016

Pamela Buttery noticed something peculiar six years ago while practicing golf putting in her 57th-floor apartment at the luxurious Millennium Tower. The ball kept veering to the same corner of her living room.

Recommended for you

Pushing lithium ion batteries to the next performance level

December 13, 2018

Conventional lithium ion batteries, such as those widely used in smartphones and notebooks, have reached performance limits. Materials chemist Freddy Kleitz from the Faculty of Chemistry of the University of Vienna and international ...

Uber filed paperwork for IPO: report

December 8, 2018

Ride-share company Uber quietly filed paperwork this week for its initial public offering, the Wall Street Journal reported late Friday.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.