The National Earthquake Information Center reports that the United States averages 12,000 to 14,000 earthquakes each year. And 16 of these earthquakes are major ones — 15 having a magnitude of 7 or more on the Richter scale, one reaching a magnitude greater than 8.
There is an often-repeated saying: “Earthquakes don’t kill people, buildings do.” Earthquake engineers are working to make buildings safer in the event of major earthquakes, which includes improving the design of new buildings and retrofitting older ones to include the latest advances in engineering.
Building a structure to withstand earthquakes starts with choosing the right materials, and steel is by far the most widely used material for building earthquake-resistant buildings. Why?
Reasons to Use Steel Framing to Withstand Earthquakes
1. Steel is Ductile
Ductile is a material’s ability to undergo significant deformation without breaking. In simple terms, ductility describes how much you can stretch or bend a metal like steel before it snaps. It’s the opposite of being brittle.
Steel exhibits ductile behavior, meaning it can deform significantly before reaching its breaking point. This ductility allows steel-framed structures to absorb energy from movement in a building caused by earthquakes, dissipating it and reducing the impact on the building’s integrity.
2. Steel is Strong
Steel is known for its exceptional strength, making it one of the most widely used materials in construction. In fact, steel has the highest strength-to-weight ratio of all structural framing materials — 7 times that of wood.
The strength-to-weight ratio is a way of measuring how strong a material is compared to how much it weighs. A high strength-to-weight ratio means the material is very strong for its weight, which is important in building structures, airplanes and cars where you want strong materials that don’t add unnecessary weight.
Materials like steel with a high strength-to-weight ratio are strong but lightweight. During an earthquake, it’s ideal to have a building free of heavy parts that might add to the forces experienced during the quake. Less mass means less inertia, which can reduce the building’s tendency to sway excessively during shaking.
3. Steel is Predictable
Imagine you are baking cookies. When you follow a recipe you have used before, you can predict how the cookies will turn out. You know the ingredients, the oven temperature and the baking time, so you know what to expect.
In the same way, engineers have a recipe for using steel framing in buildings. Based on decades of research, they know how strong steel is, how it reacts to different forces and how it holds up over time. This predictability helps them design buildings that can handle earthquakes because they can anticipate how the steel will respond.
Furthermore, steel is an engineered material that results from refining and processing iron ore with the addition of carefully selected elements. Engineers use scientific knowledge, manufacturing processes and technological innovations to create steel made specifically for buildings prone to earthquakes.
Video Credit: MRI Steel Framing
4. Steel is Non-Combustible
One concern during earthquakes is fire. Fires that can break out due to damaged electrical lines, gas leaks and other hazards. If the building is made of materials that can catch fire easily, like wood, it adds a dangerous element to an already challenging situation.
This is where non-combustible materials like steel come into play. Non-combustible means that the material doesn’t burn easily or at all. So, if the building is made primarily of steel, even if there’s a fire nearby during an earthquake, the steel will not catch fire. This is a huge safety advantage because it reduces the risk of the steel itself becoming a source of fire and spreading it further.
The use of non-combustible steel in earthquake-prone areas makes buildings safer by preventing fires from breaking out or spreading, which is crucial for protecting lives and property during and after seismic events.
5. Steel is Adaptable
Adapting, or retrofitting, a steel-framed building for earthquake resistance is generally easier and more effective than doing the same for a wood or concrete building.
In regions with older buildings that may not meet current seismic codes, adding steel elements such as braces, frames or other reinforcement can significantly enhance their ability to withstand seismic forces.
Steel is easier to modify and work with compared to concrete, which often requires extensive demolition and reconstruction for retrofitting. Steel elements can be prefabricated off site and then installed or welded into place, minimizing disruption to the building’s occupants.
Steel’s adaptability allows for cost-effective and efficient upgrades to existing buildings, improving their seismic performance and overall safety.
The University of Hawaii Atherton Hall project features cold-formed steel (CFS) framing for a rehabilitation project. Courtesy of CEMCO.
Precision in Earthquake Design
Engineers specify steel framing because they know exactly how it will behave under different circumstances, which helps to design earthquake-resistant buildings with precision.
Overall, steel’s flexibility, strength, predictability, fire safety and ease of use make it the best choice for buildings in earthquake-prone areas, ensuring buildings stay safe and strong during seismic events.
Want to Learn More?
- 5 Reasons CFS Contributes to Building Resiliency
- eBook: Strength in the Face of Disaster: How Cold-Formed Steel Framing Keeps Buildings Safe
- CFS Outperforms Wood and Concrete in UC San Diego Seismic and Fire Tests