What Causes Leaning Towers?

What Causes Leaning Towers?

You’ve heard of the Leaning Tower of Pisa – but what about the Leaning Tower of South Dakota?

In late 2023, a construction site in Rapid City, South Dakota, had to be evacuated when an elevator shaft for the 10-story, mixed-use structure began to tilt. According to local news outlet KELO, surrounding buildings and a section of a nearby street also had to be evacuated until repairs could begin.

Luke Jessen, Vice President of Development for Lloyd Construction, which is overseeing the project, said in a statement to Construction Dive that a product failed at the corner of one of the elevator shafts, causing the tower to shift one inch at its base.

A crane supporting a leaning elevator shaft.
(Photo courtesy of Rapid City Police Department via Construction Dive) A leaning elevator shaft on a mixed-use tower construction project in Rapid City, South Dakota forced the evacuation of not only the site, but the surrounding area.

“This is an isolated product and sequencing issue, which will be safely rectified by an erection subcontractor in the days to come by deconstructing the shaft.” Jessen’s statement said.

The incident in Rapid City is just the latest example of a leaning structure making the news.

The most famous is the aforementioned Leaning Tower of Pisa, the 60-meter medieval tower in Italy which stands about 17 feet off the vertical. That tower, however, is just one of several leaning structures in Pisa alone.

There are thousands of unintentionally tilted towers scattered throughout the world – and they’re not all historic structures. San Francisco’s Millennium Tower luxury condo required a $100-million foundation retrofit because it had been sinking since it opened to residents in 2009 and was tilting an estimated 14 inches by 2019.

The situation became more serious when the curtain wall – an exterior element of a building designed to protect it from the elements – had pulled away from the tower and created a gap that could have served as a funnel for flames in the event of a fire.

Determining the causes, consequences, and solutions for leaning buildings falls under a branch of civil engineering known as geotechnical engineering – also known as geotechnics – which focuses on the engineering behavior of earth materials.

In an article published in February 2020 on CNN Style, leading civil engineer John Burland – who designed the solutions that stabilized both the Tower of Pisa and Britain’s Big Ben – explained that the Earth itself is the most frequent culprit behind modern leaning towers.

“We are very sophisticated in our analysis now, but we still have to understand how mother nature works,” Burland said. “Mother nature lays down ground in all sorts of variable ways and unless you actually spend the money and the time investigating the ground properly – and employ people with good knowledge and experience – then you can run into big problems… If it’s mother nature then it’s human error because they haven’t investigated it properly.”

In addition to faulty construction materials – as was the case with the elevator shaft in South Dakota – soft or weak spots in the ground, unexpected geological faults, and incomplete ground investigations can also cause structures to lean.

Burland added that most of the leaning buildings he’s worked with are “not unsafe,” but that “selling space in a building that has been known to be leaning is very difficult because often the leaning is caused by some defect in construction or design.”

“The trouble with a tall building is that you can see it leaning, which people don’t like,” he added. “It might be safe, but the owners of the building are not going to be at all happy.”

Four GPRS Project Managers conducting utility locating services on a job site.
GPRS’ subsurface damage prevention services keep you on time, on budget, and safe whether you’re building a multi-use tower or rehabbing a bridge.

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Whether you’re building a tower or a rehabbing a bridge, GPRS offers a suite of subsurface damage prevention, existing condition documentation, and construction & facility project management services designed to keep your projects on time, on budget, and safe.

Our concrete scanning, utility locating, video pipe inspection, and leak detection services help maintain the integrity of existing infrastructure and protect it from damage during groundbreaking activities. Using a blend of technologies including ground penetrating radar (GPR) scanners, electromagnetic (EM) locating, CCTV camera-equipped sewer inspection rovers, acoustic leak detection and leak detection correlators, our SIM and NASSCO-certified Project Managers (PMs) provide you accurate, highly detailed information about where your infrastructure is located and its condition.

Accurate measurements help you avoid expensive mistakes, rewords, and change orders. GPRS 3D Laser Scanning services provide 2-4mm accuracy by capturing 2 million data points per second, for efficient planning, design, and construction. And our in-house Mapping & Modeling Team can export your GPR utility locates & concrete scans, 3D laser & photogrammetry data, and video pipe inspection reports to create accurate existing condition as-builts – above and below ground – to give you the accurate information you need in a format you can easily work with and share to keep your project on track.

All this field-verified data is available to you 24/7, from any computer, tablet, or smartphone, courtesy of SiteMap® (patent pending), GPRS’ cloud-based infrastructure mapping software solution which allows you and your team to plan, design, manage, dig, and ultimately build better.

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*Please note that GPRS does not investigate, analyze, or interpret soil composition, soil conditions, or geological or geophysical information. GPRS reports retrieved data and does not provide geophysical, geological, engineering, or land surveying services. Please contact a professional in those fields if such services are needed.

Frequently Asked Questions

Does GPRS Perform S.U.E. Work?

Subsurface Utility Engineering (SUE) reduces the risk and improves the accuracy of subsurface utility readings. It is broken down into four levels of quality, governed by ASCE Standard 38-02. GPRS provides private utility locating services but does not currently provide a fully comprehensive in-house SUE service. GPRS does not provide engineering services. If you need professional engineering services, please contact a professional engineer.

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