Nature is Warning Us: A Call to Action for Structural Engineers

Our hearts still ache as we mourn the loss of countless lives in the devastating earthquakes that struck Turkey and Syria. As rescue efforts continue, we reflect on the tragedy that could have been alleviated with better infrastructure and building design, and earthquake mitigation measures. With every column and beam, we see a call to action for a more resilient future, where the forces of nature are met with the power of human innovation. In this article, we delve into the factors that contributed to the disaster and the urgency for change moving forward.

The recent 7.5 and 7.8 magnitude earthquakes have resulted in significant loss of life and destruction. While the exact causes are complex and multi-faceted, it is important to consider the role of human factors such as urbanization patterns, building codes, and infrastructure development.?

While it is not possible to entirely prevent earthquakes, it is possible to minimize their impact through effective planning and risk mitigation measures. As structural engineers, we are tasked with ensuring the safety and stability of structures during seismic events. This is accomplished through a systematic process of seismic hazard assessment, analysis, and design.

The process begins with assessing earthquake risk by evaluating the likelihood of earthquakes occurring in a particular region, as well as their intensity and frequency. By understanding the risks associated with a particular location, we can determine the seismic forces that a structure is likely to experience. Using computational models, we then simulate structures' behavior to analyze the forces generated. This enables us to identify potential weaknesses in a structure's design and implement design strategies to enhance its resilience. Strategies may include reinforcing building elements with seismic-resistant materials and incorporating features such as base isolation.

The need for earthquake-resistant construction is a critical global challenge. With 1.5 billion people living in areas prone to earthquakes, particularly in Central and South Asia, the Middle East, and vulnerable nations, and as the world's population continues to grow, the AEC industry must find ways to address this challenge and make structures safer for communities in these regions.

Lebanon: A real seismic vulnerability?

Lebanon faces high seismic risk due to its moderate to low seismicity and major faults, which have caused historic devastating earthquakes. The country's densely populated coastal strip, particularly Beirut where most of the population and key economic activities reside, amplifies these risks.

The rapid urbanization in Beirut since 1990 has resulted in a dense cluster of heterogeneous buildings of varying heights and ages. A survey of nearly 8,000 buildings estimated that half of them would sustain significant damage under a seismic acceleration of 0.25 g. Studies have also highlighted the residents' high vulnerability to earthquakes and the need for effective protection and prevention policies tailored to the specific context in Lebanon.

In light of these challenges, it is important to recognize the significant contributions of Dr. Muhamad Harajli, an expert in Civil Engineering from the American University of Beirut. Dr. Harajli evaluated the seismic hazard map of Lebanon and proposed increasing the zone parameters to enhance the country's readiness for earthquakes. He suggested designing for a PGA of 0.3 g in the coastal region and central Yammouneh fault and 0.25 g for the rest of the country.?

Why did so many structures collapse?

Technologically and scientifically, it is feasible to construct earthquake-proof cities globally. Yet, the call for action goes unheeded due to socio-economic and political factors. The failure to address this issue is a testament to the fact that major social problems, including natural disasters, require a coordinated global solution.

It is imperative that we, as engineers and builders, consider the safety and well-being of our communities in the designs we bring to life. In contrast to the devastating outcome in Turkey and Syria, earthquakes of similar magnitude in Japan have resulted in much lower death tolls. This disparity highlights the importance and feasibility of implementing effective earthquake mitigation measures. Chile also serves as an example of successful building strategies in the face of seismic events. The evidence is clear, and the need for implementing earthquake-resistant measures in buildings is vital.

We know that in the ten provinces of Turkey, the earthquakes on Monday caused at least 6,000 buildings, including hospitals and other public facilities, to collapse. This begs the question: could more have been done to stop the devastation??

The short answer is: yes.

The number one factor that trumps everything else is building construction quality which is controlled by a building code and the enforcement of that code.?

Poor construction is a known problem and seems to be at the root of the collapses seen in the aftermath of these earthquakes. Despite the seismic building codes in the area suggesting these buildings should withstand strong earthquakes, some failed at intensities lower than the “design code” suggesting non-compliance and inadequate building construction.

Structures matter more than material. In seismic design, it is crucial to understand that the structural design of a building plays a more significant role in its seismic performance than the material used in construction. Proper structural design, which takes into account factors such as the loading conditions, lateral resistance systems, and detailing, is critical in ensuring the building's ability to withstand the effects of earthquakes. It is therefore crucial to prioritize the development of effective seismic design solutions that enhance the resilience of buildings, communities, and infrastructure.

Izmir is built on very soft, young sediments that amplified shaking. This explains why it is crucial to have a thorough understanding of soil mechanics when constructing buildings. Ignoring factors such as soil type, liquefaction potential, and the interaction between soil and structure can result in building failure during earthquakes. A thorough evaluation of soil properties, including depth and composition, is necessary to ensure stability. The location of a point in the shallow layer of soil can determine whether it amplifies vibrations in a way that reinforces the structure of a building, or causes it to destabilize and collapse. Also, the location of a building's foundation can significantly impact its ability to withstand seismic vibrations, and the interaction between neighboring buildings and their unique soil conditions can also play a role in the stability of a structure.

The term soft story refers to a building level weaker in resisting lateral loads than adjacent levels. According to the International Building Code (IBC), this means it has a 70% or greater reduction in strength compared to other floors in the building. These buildings are vulnerable to seismic shaking, leading to weaker connections and increased swaying during earthquakes. Unfortunately, in Turkey, soft-story buildings make up a significant portion of residential and commercial buildings.

The recent quakes underscore the need to overhaul old infrastructure everywhere. The pancake collapses seen in the aftermath are devastating, making rescue efforts challenging, and stand in stark opposition to the principles of sound seismic codes and design practices.

The 1999 Marmara earthquake was a wake-up call for building codes in Turkey, leading to much-needed updates. However, it is clear that many older structures were left behind and are now paying the price. It is evident that the "strong column, weak beam" principle was not a priority in their design, resulting in these devastating pancake collapses where vertical components of buildings, such as walls and columns completely failed, and the heavy floors fell on top of each other instead of sturdy "life triangles."?

The "life triangle" refers to a design principle where the beams and columns of a building are proportioned such that the beams are weaker than the columns, thus creating a robust structure. In case of an earthquake, the columns are intended to remain standing while the beams give way, creating a triangle of life in the void created between the fallen beams and the standing columns. This void provides space for occupants to survive until rescued, hence the term "life triangle." The principle of this design is based on the "strong column, weak beam" concept, where the columns are designed to be strong enough to resist the earthquake forces, while the beams are designed to be weaker so that they can deform and absorb some of the energy, preventing the collapse of the entire structure.?

Seismic Lessons Learnt

Ductility is key. As earthquake engineers, it is our responsibility to integrate this concept into our designs and ensure that our structures are not just compliant with building codes but are also equipped to withstand the forces of nature. The most important factor in ensuring a building's ductility is the proper connection of its floors and walls through the use of joints. Joints should be designed, detailed, and constructed to provide a strong and flexible connection that allows the building to absorb the energy of an earthquake without collapsing. It is critical that architects, engineers, and building officials take this into account when creating and enforcing seismic codes and regulations.?

Seismic design codes: It is important for engineers, architects, and building contractors to be well-versed in these codes and to follow them closely in their design and construction work. Follow-through on compliance is crucial.

Strong foundation: The foundation of a building is the first line of defense against earthquakes. It is important to ensure that the foundation is designed and constructed to provide a solid base for the building, especially in earthquake-prone areas.

Retrofitting: While retrofitting old buildings may seem like a costly investment in the short term, it is actually a crucial step in improving their resilience. By upgrading the structures to better withstand seismic events, the risk of collapse and extensive damage is significantly reduced. Over the long term, retrofitting is not only a smart investment but also a cost-saving measure, as it curbs the expenses associated with rebuilding or repairing heavily damaged structures in the aftermath. ? ? ? ? ?

Forensic analysis: We must go beyond attributing the failure to socioeconomic and political factors, corruption, or substandard construction practices to get the complete picture. By gaining a deeper understanding of the factors that contribute to building failure, we can strive towards improving building standards and preventing similar disasters in the future.

Urban configuration: With most cities expanding spatially faster than the rate of their population growth, urban configuration must be carefully carried out before infrastructural constraints hinder the reconfiguration of these rapid growing cities. We must prioritize assessing hazard parameters for essential buildings, including hospitals, schools, emergency response facilities, infrastructure facilities, historic buildings, and high-rise buildings, to ensure their safety and security in the face of earthquakes. This requires a global coordinated effort to meet specific seismic parameters in their location, configuration, and construction.

Conclusion

The recent earthquakes in Turkey and Syria have raised important questions about the role of earthquake mitigation measures and the responsibility of various stakeholders in ensuring the safety of buildings and communities. While it may be tempting to attribute the destruction solely to the forces of nature, it is important to acknowledge the significant role that human actions and inaction play in determining the outcome of such events.?

Despite the advancement of seismic design and engineering techniques, it is evident that there is still a significant gap between what is possible and what is being implemented in practice.

Mitigating earthquake risk is a shared responsibility that requires collaboration between various parties. The government has a significant role to play at the institutional, sectoral, and local levels, but the expertise of structural engineers is also crucial in ensuring the safety of structures. Through the implementation of appropriate building codes, the use of seismic-resistant materials and techniques, and ongoing maintenance and inspection, we can reduce the risk of damage and loss of life.

As leading professionals in the engineering industry, it is our responsibility to raise awareness among the public and decision-makers regarding the risks associated with insufficient seismic reinforcement and advocate for the implementation of evidence-based mitigation measures that aim to secure the structural integrity and safety of buildings. This requires a comprehensive understanding of the seismic hazard and the underlying soil mechanics, as well as an appreciation for the complexities of large-scale urban infrastructure.

The fact is, earthquakes can and will happen, and their impact on communities can be devastating. It is therefore imperative that we invest in the necessary research, technology, and infrastructure to ensure that our built environment can withstand the forces of nature. It is also crucial for all stakeholders, including governments, building owners, and design professionals, to prioritize the implementation of earthquake mitigation measures in high-population urban areas. Proactive steps must be taken to address any potential vulnerabilities.

Let us not forget the lessons of the past, and let us strive to build a safer and more resilient future, for the benefit of all.