Moderate to severe earthquakes can cause vast damage to buildings and their foundations, endangering the lives of residents and leading to complex and costly search, rescue, and cleanup efforts.
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These seismic events are not uncommon: on average, over the past 25 years, there has been nearly one earthquake per year that has resulted in more than 2,000 fatalities.
The devastating earthquake in Haiti in 2010 caused at least 100,000 deaths, with estimates from the Haitian Government suggesting the toll could be as high as 316,000. In 2005, a magnitude 7.6 earthquake killed over 80,000 people in the Kashmir region of Pakistan.1
Around half a billion people now live in tectonically active zones, and this figure is growing. While new buildings in many areas, such as Japan, are designed to withstand the devastating impacts of seismic events, there is an urgent need to retrofit existing structures to protect lives and livelihoods.
This article will discuss seismic retrofitting and current innovations in the field.
The Basics of Seismic Retrofitting
Seismic retrofitting strategically identifies and eliminates structural deficiencies to enhance the earthquake resilience of buildings. This process is beneficial for all types of structures, including apartment complexes, commercial buildings, and critical infrastructure that must remain operational after an earthquake.
The goal of seismic retrofitting is to minimize the loss of life, facilitate quicker and more cost-efficient recovery, and prevent catastrophic damage to structures, allowing them to be brought back into use sooner. Protecting commercial and industrial buildings also helps reduce financial losses.
Buildings can be fortified to resist seismic movement and subsequent damage. This is the basis of the science of seismic retrofitting. Recent advances in understanding seismic events and building technologies have led to new approaches focusing on flexibly absorbing and dissipating the energy generated during seismic events.
Common seismic retrofitting techniques include base isolation, foundation strengthening, damping devices, the addition of shear walls and steel bracing, mass reduction, and retrofitting non-ductile concrete structures. Some approaches also involve upgrading internal electrical and mechanical systems.2,3
Innovations in Seismic Retrofitting Techniques
Advancements in technology and materials have reshaped the field of seismic retrofitting.
Fiber-reinforced polymers (FRPs) are vital in enhancing the ductility and strength of existing structural elements. Composed of strong fibers, often carbon, embedded in a polymer matrix, FRPs are lightweight and robust. Their thin nature minimizes disruption to existing spaces without adding significant bulk or weight.
Shape memory alloys (SMAs) are innovative materials that can return to their original shape after deformation and can thus absorb and dissipate energy during seismic events to limit structural damage. They are commonly used in braces and dampers.
Cold-formed steel (CFS) is a material with a high strength-to-weight ratio. It plays a crucial role in reducing a building's seismic mass, thereby diminishing the seismic forces acting upon it (as the seismic force exerted on a structure is directly proportional to its mass).
Base isolation systems are a technological solution in which isolators are placed between a building’s superstructure and its foundations. This method requires lifting the entire structure slightly and often necessitates substantial new foundations. Nevertheless, it significantly reduces stress and damage by absorbing energy and allowing the building to move independently from ground motion.
Alongside technical and material innovations, digital techniques are increasingly important. 3D laser scanning allows precise, high-fidelity documentation of structures and modifications, surpassing many traditional method limitations. Computer analysis pinpoints vulnerabilities, while sophisticated simulations provide insights into potential seismic events and potential failure points.
Emerging industry 4.0 technologies, such as artificial intelligence (AI), machine learning, and digital twins, further enhance these digital approaches, providing unparalleled capabilities. Drones enhance inspection and execution, accessing hard-to-reach areas and bringing high-resolution imaging techniques to the architect and engineer’s toolkit.2
Innovations in Action
Companies such as Salas O’Brien and Freyssinet4 are harnessing cutting-edge materials and technologies to protect buildings and lives against seismic events, offering tailor-made seismic retrofitting solutions to clients in tectonically active zones.
Researchers from the Department of Civil Engineering and the Department of Project Culture in Italy have introduced a concept involving panels made of engineered insulating concrete to form a retrofitted seismic exoskeleton shell. The proposed technology considerably increases a retrofitted building’s lateral stiffness and, combined with non-dissipative behavior, reduces any seismic deformation.5
In 2022, a paper published in Engineering Structures6 presented a novel seismic retrofitting system composed of textile-based capillary tube-embedded reinforced concrete panels. This system enhances a building’s thermal performance and seismic response. Tests and modeling confirmed that this solution significantly improves stiffness, strength, and displacement capacity.
Vailati and colleagues, in a 2018 publication, introduced a novel system that incorporates recycled plastic joints in a mortar-free infill system. Phase Changing Materials have also been proposed as materials for infill systems. Exoskeleton interventions, roof and floor strengthening techniques, envelope interventions, window and opening interventions, and many other approaches are currently being explored. 7
The Future of Seismic Retrofitting
Several research areas promise substantial enhancements to the efficacy of seismic retrofitting systems. Innovations in smart materials, Phase Changing Materials, nanotechnology, and the incorporation of renewable energy sources represent just a few of the technological pathways scientists and engineers are exploring.
The increasing role of AI and other relevant Industry 4.0 technologies in seismic engineering and retrofitting cannot be understated. These technologies are set to empower professionals in the field with new and innovative capabilities that surpass traditional approaches.
The role of advanced materials and technologies and ongoing innovation in this field will continue to protect lives and livelihoods in tectonically active zones. This ongoing evolution will enhance the seismic performance of existing building stock, from small residential properties to critical infrastructure such as bridges, dams, and power stations.
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References and Further Reading
[1] The Associated Press. (2023). The world's deadliest earthquakes in the past 25 years, at a glance. [Online] NPR. Available at: https://www.npr.org/2023/02/09/1155836898/deadliest-earthquakes-list (Accessed on 27 March 2024)
[2] Westphal, J., McMillan, D., Bolding, J. (2024). How advanced technologies are reshaping the landscape of seismic retrofitting. [Online] Salas O’Brien. Available at: https://salasobrien.com/news/seismic-retrofitting/ (Accessed on 27 March 2024)
[3] Nasreen, S. (2024) Seismic Retrofitting Techniques for Concrete Structures. [Online] The Constructor. Available at: https://theconstructor.org/concrete/seismic-retrofitting-techniques-concrete-structures/11767 (Accessed on 27 March 2024)
[4] Freyssinet. Seismic retrofitting. [Online] Freyssinet. Available at: https://www.freyssinet.com/solution/repair/seismic-retrofitting/ (Accessed on 27 March 2024)
[5] Pertile, V., et al. (2021) Seismic and Energy Integrated Retrofitting of Existing Buildings with an Innovative ICF-Based System: Design Principles and Case Studies Sustainability. doi.org/10.3390/su13169363
[6] Baek, E., et al. (2022) Innovative seismic and energy retrofitting of wall envelopes using prefabricated textile-reinforced concrete panels with an embedded capillary tube system Engineering Structures. doi.org/10.1016/j.engstruct.2022.114453
[7] Pohoryles, DA., et al. (2022) Integrated seismic and energy retrofitting of existing buildings: A state-of-the-art review. Journal of Building Engineering. doi.org/10.1016/j.jobe.2022.10527
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