Engineer backs seismic isolation as hospitals stood tall during Turkey-Syria quakes

For instance, due to seismic isolation systems built into their design, two hospitals—Elbistan State Hospital and Malatya Maternity and Children's Hospital—located in the epicenter of these earthquakes both survived unharmed and remained in use.

Many of the world's tallest buildings, like the Taipei 101 in Taiwan and the Burj Khalifa in Dubai, use seismic isolation systems to protect against earthquakes.

To gain insight into the use and status of seismic isolation systems during the Turkey-Syria earthquakes of 2023, Interesting Engineering (IE) connected with Professor Osman Ozbulut in the Department of Civil and Environmental Engineering at the University of Virginia.

Turkey-Syria quakes acted as a proving ground for seismic isolation systems

"The social and economic impact of the earthquakes in my homeland of Turkey and in Syria has dramatically changed life for millions," Ozbulut told IE.

He continued by pointing out that, going forward, what needs to be taken into account are factors that are not as obvious as the immediate impacts but how we view and accept global seismic risks.

"Ironically, amidst the seismic waves of destruction, the earthquakes provided a proving ground for advanced building technologies that can not only prevent building collapse but also minimize damage," he said.

"Several hospitals built with seismic isolation systems—in the cities where heavy damage was sustained in surrounding buildings—survived the earthquakes with almost no harm."

Ozbulut stressed that healthcare facilities are essential in post-disaster response and recovery, so ensuring their functionality after a major earthquake is critical.

He argued that this requires minimizing not only structural damage but also damage to nonstructural components and technological contents of the buildings, which can account for up to 90 percent of the total value of such buildings.

Turkey has seen a considerable rise in the number of isolated buildings since the 1999 Izmit earthquake. The Turkish Ministry of Health also announced a new policy in 2013 requiring seismic isolation for all healthcare institutions constructed in earthquake-prone areas.

"There were nine isolated, reinforced concrete hospital buildings, four of which were still under construction, in the region affected by the latest earthquakes," he highlighted.

"At least 15 conventional hospitals without these systems suffered partial or severe damage when the people of Turkey needed them most, revealing the importance of using advanced seismic technologies in buildings, especially in critical facilities."

The art of seismic isolation systems: So how do they work?

Ozbulut explained that seismic isolation systems minimize the effects of earthquakes by preventing the transmission of seismic energy into the buildings in the first place.

"This is achieved through the installation of seismic isolator devices, commonly either elastomeric or sliding bearings, between the foundation and building," he added.

"These devices shift the natural period of the structure out of the dominant seismic energy and minimize the deformations of the building components, i.e., damage."

The basic idea is to create a flexible layer or series of layers between the building and the ground so that when an earthquake occurs, these layers move and stretch, absorbing much of an earthquake's impact by reducing swaying and shaking of the building. By separating the structure from its base, the amount of energy that is transferred to the building during an earthquake is reduced significantly.

The most common type of seismic isolation system is called a base isolation system, which typically involves placing a layer of specially designed bearings or pads between the building and the foundation.

These bearings can be made from various materials, including rubber, steel, and lead, and are designed to deform and absorb energy during an earthquake while also providing a stable base for the building.

"Seismic isolation is one technology that can be used to design structures for higher seismic performance. There are several other design approaches that can be used as well," he stated.

While Ozbulut didn't go into detail about these other approaches, one is a friction pendulum system. These use a pendulum-like device to absorb seismic energy. Another method is called an elastomeric isolation system, which uses layers of rubber-like material to absorb energy and provide flexibility.

Ozbulut also introduced IE to the concept of 'functional recovery.' He described this as "a performance objective where buildings are not only designed and constructed to avoid collapse during a strong earthquake but also to prevent damage and enable re-occupancy within an acceptable period."

"Buildings designed for functional recovery will let the occupants use their home immediately after the quake or in a reasonable time," he added.

Earthquake-prone regions can take proactive action

Ozbulut noted that modern seismic design codes call for building elements like beams and columns to be capable of sustaining controlled damage during an earthquake so that the structure remains standing and safeguards inhabitants.

"This performance objective is called 'life safety' and has been deemed sufficient until recently," he said.

"Recent earthquakes in different parts of the world have shown that the damage to the buildings designed with modern codes was so extensive that many buildings had to be demolished after the quake. This has a huge social and economic impact."

He emphasized that it is especially vital for certain essential facilities, such as hospitals, police stations, and fire stations, to remain functional after an earthquake.

"In addition, the damage to buildings with high-value technological contents or certain industrial buildings, as well as those located in the finance centers of a region, may have much higher economic impacts," he said.

Seismic isolation can successfully be implemented to protect such structures, he urged. "As long as there is a demand for more resilient structures, such systems can also be used for low-to-medium-height residential buildings."

"Many are willing to pay a bit more to drive safer cars, and those who live in high seismic hazard regions may prefer investing in safer homes," he reasoned.

When asked about any critical thoughts or takeaways in light of the large number of collapsed buildings in Turkey and Syria following the most recent quake, Ozbulut suggested that the risks and economic and social benefits of conventional design and enhanced design should be better communicated.

"[This should be directed to] building owners and the public through mass media and state or federal policies," he stated.

"Instead of paying massive amounts for restorative cleanup, we need to be proactive and design structures to perform better during an earthquake and minimize damage."

"We need to act now before the next 'big one' costs more lives and the stability of entire countries. Let's topple the status quo," Ozbulut concluded.