February 6, 2023, earthquakes in Turkey and Syria damaged more than 100,000 buildings, caused more than 10,000 collapses and killed more than 50,000 people. These earthquakes also challenge advanced construction technologies that can minimize damage and keep buildings functioning after an earthquake.
Several hospitals built with such technology – called a seismic isolation system – survived the earthquakes with almost no damage, according to local news reports, even as surrounding buildings sustained heavy damage.
The Adana City Hospital was built to capture ground vibrations as well as the response of the building. Thanks to the seismic isolation system, the building saw 75% reduction of shaking, according to the company that designed the insulation system, compared to neighboring structures. This system allowed the building to continue to operate after the earthquake.
Engineers are not surprised that the hospitals with seismic isolation systems survived with minimal damage, but on my work as a civil engineerI’ve heard people in Turkey and abroad ask why more buildings aren’t using these smarter engineering technologies.
A year after the 1999 Izmit earthquake in Turkey killed more than 17,000 people, I moved to Istanbul for a bachelor’s degree in civil engineering. I moved to the US in 2005 for my graduate research and since then I have been working on advanced technologies and materials that can ensure the rapid recovery and reoccupation of buildings after a strong earthquake.
While we’ve seen the effectiveness of seismic protection technologies during previous major earthquakes, these technologies have only been installed in a small fraction of places where they could potentially be useful.
Earthquake-resistant construction technology
Engineers can determine how structures respond to earthquakes in several ways.
Traditional approaches rely on certain components of the building, such as columns or beams, to absorb the energy of the earthquake. However, this method can cause damage to accumulate in these structural features can make the building uninhabitable.
Earthquake resistant systems such as seismic isolation devices and seismic dampers minimize the seismic energy entering these columns or beams by absorbing or diverting it. As a result, the building experiences less movement and damage and the risk of this is greater remain functional after an earthquake.
Seismic isolation systems prevent seismic energy from entering buildings by using devices made of rubber or steel plates coated with a friction-generating material that slide on top of each other to minimize the impact of an earthquake. These isolation devices are installed between the foundation of the building and the building itself. Alternatively, seismic dampers installed in each floor of a building can absorb earthquake energy like shock absorbers in a car and convert it into heat energy to minimize damage.
Both seismic isolation systems and seismic dampers can help a building to “functional recovery— a performance goal where buildings are constructed to prevent damage and allow for rehabilitation. Designing such buildings will not only save people and buildings, but also prevent the earthquakes from collapsing communities and economies.
While functional restoration is an emerging idea for building earthquake-resistant structures, global modern building codes stipulate that structures must at least have measures to prevent the building from collapsing – the so-called life safety goal. Buildings that follow a life safety objective are designed to take damage in a controlled manner, to keep the building upright and protect those inside.
While these buildings are unlikely to collapse, they may not be safe to use after an earthquake. While this is not the same as functional recovery, thousands of lives could have been saved in Turkey and Syria if more buildings had been built to a life-safety threshold.
The case in Turkey
Much of the damage in Turkey occurred in non-deformable concrete buildings built under a pre-1998 Turkish building code. Ductile concrete building elements, required by newer building codes, are more flexible due to steel reinforcing bars in critical locations. They can to accommodate construction movements caused by earthquakes. The older non-deformable buildings also often had poorly placed steel reinforcements, making them vulnerable to the sudden collapse of building columns.
Likewise, many so-called soft storey buildings were damaged in these earthquakes. A soft floor is a level that is significantly more vulnerable to lateral earthquake forces than the other floors in a multi-storey building. The first floors of these buildings – often used for commercial purposes such as shops, garages or office spaces – generally have more open spaces and fewer structural components, such as beams and columns, making them vulnerable to collapse.
These types of buildings can be found all over the world, including in densely populated, seismically risky areas such as Istanbul, San FranciscoLos Angeles and Vancouver – all near active fault lines.
Buildings designed under old codes can be reinforced to meet a life safety performance threshold. However, these upgrades can cost a lot of money, and enforcing these upgrades, especially for private buildings, requires well-planned policies.
While buildings designed for life safety can protect thousands of lives, the February 2011 Christchurch earthquake in New Zealand revealed the limitations of modern seismic codes focused solely on this design goal. The damage to buildings designed under a life safety objective was so great that there must have been thousands demolished after the earthquake.
It was this earthquake that led engineers to focus on “functional recovery” and deploy seismic protection technologies on a larger scale. The additional costs of such technologies for seismic protection is typical less than 5% of the initial construction costs and pales in comparison to the cost of the social and economic disruption caused by a major earthquake. In addition, securing lower insurance premiums can recoup most of these initial costs.
Total economic losses following the Christchurch earthquake were estimated at 32 billion dollars, not accounting for inflation, of which $24 billion was construction costs. The cost of the recent earthquakes in Turkey is estimated to be more than $84 billion and still counting.
The earthquakes in Turkey have shown that seismic protection technologies work. To avoid major economic and social impacts, local authorities can update the provisions and codes for designing new buildings to allow for post-earthquake reoccupation and functional recovery. In addition, policies, financial incentives and tax incentives that promote better building design could improve seismic safety on a larger scale.