If you’re in the beginning stages of a new project, now is the ideal time to begin working against potential hazards. One hazard that can be especially devastating to any structure is an earthquake. Earthquakes are fiercely powerful, completely unpredictable, and cause costly damage. As such, no building can be completely earthquake-proof — but if you’re wondering how to construct earthquake-resistant buildings, there are many construction requirements to consider.
From soil analysis to ribbon-cutting, working to prevent earthquake damage is critical at every juncture. What’s more, designing buildings with potential earthquake damage in mind is a requirement in most jurisdictions (ASCE 7-16 code for new construction and the ASCE 41 code for seismic retrofits). Learn about the requirements of constructing earthquake-resistant buildings and the requirements of earthquake-resistant building construction with our team below, to ensure the greatest possible success against earthquake damage.
Earthquake Construction Methods: Understanding Your Soil
A thorough site investigation is the only place to begin when getting started on a new project. This is especially true when building in a seismic hazard zone. A seismic hazard zone is an area near a focus point for earthquakes, where damage can occur as a result of seismic activity, like much of our local service areas in the Pacific Northwest and Alaska—or across the nation. Acknowledging your proximity to a seismic zone is important, but it is not enough. It is crucial to understand that seismic activity impacts different types of soil and construction types in unique ways.
Conducting extensive soil testing to identify the characteristics of your soil will guide your design process towards mitigating risk. Your site may have hard rock, dense soil, soft soils, or even man-placed fill below the surface. An earthquake will impact a site with hard rock subsurface conditions differently than one with soft clays, even if they are equidistant from the seismic epicenter. Generally, the impact of an earthquake on a property is based on the softness of the soil or rock and the total thickness of the material above the bedrock.
The geology and soil parameters on individual sites will determine the size of seismic waves beneath the surface. The larger the waves, the greater the shaking and thus the risk of damage. The National Earthquake Hazards Reduction Program (NEHRP) defines six different site classifications, with A being the hardest and F being the softest:
- A: hard rock
- B: rock
- C: very dense soil and soft rock
- D: stiff soil
- E: soft soil
- F: Other
While you can’t always choose the ideal subsurface conditions at a site, you can use your understanding of the soil to deploy proper damage mitigation design elements.
Earthquake Construction Methods: Design Techniques
Through proper site investigation, you can gain a better understanding of the risk associated with your property, and your geotechnical engineer can provide appropriate design parameters. Applying the correct engineering principles as appropriate is determined by the site soils, and is especially important when building in zones with high seismic activity.
Depending on the proximity of your site to a seismic hazard zone or known fault, the requirements of earthquake-resistant building construction may be stricter. If you’re building in an area of this nature, an earthquake may happen and damage is likely. However, through strategic planning and design, you can reduce the risk of hazard and any damage substantially.
After a proper investigation into the geotechnical parameters of a given project, things that structural engineers must prioritize when building an earthquake-resistant structure include:
Stiffness and Strength
Earthquakes will cause left-to-right shifting and shaking of a structure. Focusing on both vertical and lateral stiffness and strength can reduce the damage an earthquake can cause to a building.
Regularity is a principle similar to the old adage, “a chain is only as strong as its weakest link.” Irregular buildings have weak spots that will fail when seismic activity is introduced. Constructing a building that can equally dissipate vibrations laterally will fight against earthquake damage.
Redundancies ensure that there are multiple safety measures in place should one fail. While this can add to the building costs, the structural integrity of your building is invaluable, and the price pales in comparison to the cost of severe earthquake damage.
Shear walls, cross braces, horizontal frames, and movement-resisting frames can be implemented to accommodate the unique challenges of the foundation at your site. This stage underlines the importance of understanding the subsurface conditions, so you can brace your foundations accordingly.
Continuous Load Paths
The overall connectedness of every element in a structure is critical. As seismic waves pass through a building, disjointed components can move independently and cause serious damage. The continuous load path is the way seismic waves travel through a building both laterally and vertically, so stability throughout the entire journey of the earthquake’s vibrations is key.
Earthquake Construction Methods: Resistant Materials
While specific elements like shock absorbers can resist seismic activity, using materials that can withstand stress and vibration, wherever possible, is critical. In order to have success in protecting your building against earthquakes, your materials must have high ductility. Ductility refers to the ability of any given material to withstand deformation and tension.
A variety of materials are suitable for building structures within a seismic hazard zone and can be incorporated into your build to resist earthquake damage. Earthquake damage-resistant materials include:
- Structural Steel: is combined in multiple shapes to allow the steel to bend without breaking.
- Wood: is a lightweight material that offers surprisingly strong resistance to seismic activity thanks to a favorable weight-to-strength ratio.
- Bamboo: can be shaped in multiple ways and also offers strong resistance to shaking.
- Memory Alloys: are designed to endure heavy damage and revert to their original shape.
Consult With Central Geotechnical Services
As we have discussed, constructing completely earthquake-proof buildings is not possible, but there are many earthquake-damage-resistant building techniques that can be deployed to protect your public, commercial, or residential property. If you would like to further discuss the appropriate requirements of earthquake-resistant building construction for your job, get in touch with us today. We would love to hear about your upcoming project and offer our experience and know-how for your benefit.