By Holly Schaubert
As the world faces increasingly frequent and intense natural disasters, ensuring the nation’s infrastructure is built to last has never been more important. Natural disasters often occur concurrently or in rapid succession, making a multi-hazard approach essential. By considering various types of disasters during the design and construction phase, infrastructure can be better prepared to withstand multiple threats, ensuring the safety of communities. Additionally, selecting the right materials throughout the project is pivotal in enabling structures to withstand whatever Mother Nature may bring.
Steel Hollow Structural Sections (HSS) emerge as a standout choice for fortifying infrastructure against natural disasters. With their exceptional strength, ability to withstand substantial forces, inherent fire resistance, and corrosion-resistant options, HSS offer reliable protection for structures required to endure and recover from the impacts of natural disasters involving wind, flooding, fire, and seismic activity.
Beyond their strength, HSS also contributes to sustainable and resilient practices. Their use supports the circular economy, reduces strain on supply chains and conserves finite resources. This article will delve into the critical role that steel, particularly Hollow Structural Sections, play in fortifying infrastructure from damage due to natural disasters like hurricanes, wildfires, earthquakes and other extreme environmental events. It will also explore the broader significance of steel in sustainable building practices, highlighting the interplay between resilience and sustainability in infrastructure development.
The state of our nation’s infrastructure
One-third of the continental United States is considered a “hazard hotspot”, yet nearly 60 percent of structures in the United States are located in these hotspots. Approximately 1.5 million buildings are located in hotspots with two or more hazards, leaving them vulnerable to the effects of natural disasters including floods, wildfires, tornadoes, earthquakes and hurricanes, according to a study from the American Geophysical Union. Development in these areas continues to grow.
In its most recent assessment of the nation’s bridges, the American Society of Civil Engineers found more than 46,000, or 7.5 percent, are structurally deficient. The collapse of the I-95 bridge in Philadelphia in June 2023 disrupted travel for an estimated 160,000 drivers per day, including 14,000 commercial trucks. Structural failures in the nation’s bridges also come with a higher cost: the deadliest bridge collapse in modern US history killed 46 people.
The cost to repair or replace outdated bridges in the U.S. is an estimated $125 billion. The Bipartisan Infrastructure Law designates $40 billion toward bridge repair and reconstruction – the largest single investment in bridges since the Eisenhower era, yet not nearly enough to cover the needed repairs.
Based on data from insurance and property claim services, state agencies, the US. Army Corps of Engineers, and FEMA, damages due to weather and climate disasters in the US exceeded $165 billion in 2022 alone.
While the use of Hollow Structural Sections won’t immunize a building or bridge from damage due to natural disasters, HSS do possess the highest strength-to-weight ratio of traditional construction materials and efficiently fortify against natural disasters. The adaptability of HSS also allows for easier modifications and retrofits, catering to changing infrastructure needs. Retrofitting existing structures to meet updated codes is critical to improving community resilience.
As structural engineers continue to focus on operational and embodied carbon, resilient building designs and products have become an integral part of any project’s effort to reduce emissions and future-proof its design. The U.S. Green Building Council’s RELi (Resilience and Environmental Leadership) standards emphasize integrating resilience measures into infrastructure projects, particularly in the face of natural disasters and climate change impacts. These standards incorporate hazard mitigation, adaptive design, and community engagement, enabling infrastructure to better withstand and recover from natural disasters and climate change impacts, ensuring the safety and well-being of communities. Furthermore, the RELi standards encourage the use of sustainable materials and environmentally sensitive design practices, promoting long-term sustainability and reducing the environmental impact of infrastructure projects. By combining resilience and long-term sustainability, steel and HSS provide a holistic solution to infrastructure development that prioritizes both the immediate and long-term needs of communities in the face of natural disasters and environmental challenges.
The benefits of HSS in construction and engineering
HSS possesses inherent properties that contribute to resilience throughout a structure’s life cycle.
Hazard preparedness and mitigation
The use of HSS is an ideal structural solution due to its strength and durability, helping withstand substantial forces and extreme environmental events. HSS, along with other steel structural products, reduce concerns related to fire resistance, as steel is non-combustible, and can be coated or painted to protect against water damage, corrosion, and normal wear and tear – factors that can have a greater impact on the strength and durability of other building materials.
If damaged, HSS can be repaired using a method called hot bending, which involves using a direct flame or furnace to make the metal pliable, then bending the member to the desired radius. This method is commonly used to straighten bridge girders after structural damage occurs, reducing repair time, minimizing demands on strained supply chains, and reducing material sent to landfills.
Sustainability and life cycle impact reductions
Structural steel production in the United States relies predominantly on electric arc furnaces (EAF). These furnaces offer significant advantages over alternative methods for melting and refining steel. Notably, EAFs are renowned for their superior efficiency, allowing for a more sustainable and resource-conscious manufacturing process. By emphasizing the utilization of electric arc furnaces, the United States is taking significant strides toward a more sustainable steel industry. This approach not only helps preserve natural resources, but also contributes to the global effort of mitigating climate change.
One of the most notable benefits of using electric arc furnaces is their significant contribution to recycling efforts. Structural steel produced using electric arc furnaces boasts an impressive average recycled content of 93 percent. By utilizing scrap steel as their primary input, EAFs help reduce the dependence on raw materials extracted from the earth.
Unlike concrete and wood, steel is also infinitely recyclable. Once steel has outlived its initial life purpose, it can be fully recycled and transformed into other steel products repeatedly, without impacting its strength and durability. In fact, 98% of structural steel is recycled at the end of its initial life.
Steel is the most recycled material by weight in the world, significantly reducing the energy and carbon associated with creating virgin steel products from iron ore. Additionally, due to their light weight relative to their high capacity, the use of Hollow Structural Sections can result in lighter buildings, with smaller foundations, as well as more efficient transportation. These are just some of the reasons steel and HSS should be considered when designing for sustainability.
As the engineering industry embraces more sustainable standards and building practices, resilient building materials play an integral role. The use of HSS offers hazard preparedness, mitigation, and sustainability throughout the life cycle, delivering a holistic, sustainable solution through infrastructure that’s built to last.
Holly Schaubert, PE, serves as the HSS Director for Steel Tube Institute (STI). With an extensive 19 year career, including 16 years dedicated to the steel sector, Holly possesses a wealth of practical knowledge in the construction industry. Prior to her role at STI, Holly held key positions in engineering, business development and leadership across 3 Nucor companies: Verco Decking, Nucor Building Systems and Vulcraft. Holly is a graduate of Cornell University, where she earned both Bachelor of Science and Master of Engineering degrees in Civil and Environmental Engineering.