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The 2024 model building codes are well into their development processes; it may seem early to discuss the information related to them as many jurisdictions take years before they are adopted. However, the publication and use of these documents will be here before we know it. Also, the newest versions are sometimes referenced even before formal adoption, as they represent the newest and most up-to-date information available.
One of the challenges with creating the model building codes is aligning the reference documents as there are many, each developed by different groups that include subject matter experts for the specific topic. Yet, when they all come together as part of the building code, it is important to look at how they impact each other.
When this review occurred for the 2022 editions of ASCE/SEI 7: Minimum Design Loads and Associated Criteria for Buildings and Other Structures and NFPA 13: Standard for the Installation of Sprinkler Systems, it was discovered that there was a correlation issue related to the expected earthquake forces.
You may ask, “Why would this be?” The answer is different groups produced the standards during the same timeframe. Now that both documents are published, efforts are progressing to ensure they are aligned for the next publication of the building codes, where both standards will be enforced.
To address the differences, a Tentative Interim Amendment has been proposed to the National Fire Protection Association to modify the seismic coefficient, Cp. It represents default values related to the information for earthquake loads in ASCE/SEI 7 and a few other pieces that tie to the updated anticipated earthquake forces.
The expectation is that this will be processed and become part of the 2022 edition of NFPA 13 (https://bit.ly/3OFSRFa) before the 2024 model codes are published so the seismic protection of water-based fire protection systems can be applied harmoniously with the other reference standards.
Another related update useful for those working with seismic forces is the American Society of Civil Engineers 7 Hazard Tool (https://asce7hazardtool.online). This publicly available tool was developed for the information in ASCE/SEI 7-22 (https://bit.ly/3qak9Jz). It allows users to input an address, which quickly pulls up a map of the location. Then users select the load options they seek (wind, seismic, snow, etc.) while confirming the edition of ASCE/SEI 7 and the risk category for the building.
If information on the soil is available, it can also be input, or the default values can be used. The tool will produce results and the appropriate details for the selected loads. An example would be when selecting seismic loads, the design spectral response acceleration parameter at short periods, SDS, for the site would be available. This value is now needed to calculate the seismic coefficient for use in NFPA 13.
For the 2022 edition, this tool has replaced the maps previously used within ASCE/SEI 7.
Seismic Design Categories and Fire Protection Systems
One of the most frequent questions continues to be: Do I need earthquake protection for my water-based fire protection system? Determining when a building and its systems must be protected from earthquake forces remains the same for the new edition.
The foundational concept for making this decision is based on the assigned Seismic Design Category (SDC) for the building; this is determined following ASCE/SEI 7. In most cases, this information should be available with the project details as the SDC is determined for the building, including its components and mechanical systems.
The SDC ranges from A through F: small earthquake impact (A) to great earthquake impact (F). When looking at fire protection systems, earthquake protection is not required if a building is in SDC A or B. For SDC C through F, earthquake protection will be required.
This is slightly different than other mechanical systems as fire protection systems are life safety systems; the higher associated importance factor, Ip, requires seismic protection for SDC C. In addition, earthquake protection may be required from sources outside of the standards, such as an insurance carrier.
It is always important to use coordinated documents for the best possible performance of a building. The primary goal for water-based fire protection systems subject to earthquakes is for them to work with the building in which they are installed: move with parts that move and remain rigid for parts that are stiff. This protects the system(s), allowing for operation post-earthquake should a fire event occur.
NFPA 13 works diligently to ensure the seismic criteria function with building requirements. This means the 2016 and 2019 editions of NFPA 13 will coordinate with ASCE/SEI 7-16, and the 2022 edition (and eventually the 2025 edition) will coordinate with ASCE/SEI 7-22. These corresponding editions must be used together so buildings and their systems work harmoniously during an earthquake. l
Hugo, CBO, Jeffrey M. and Valentine, PE, Victoria B. “IBC, ASCE 7, NFPA 13 – Upcoming Changes to Seismic Protection,” Sprinkler Age
Valentine, PE, Victoria B. “Do You Need Seismic Protection?” SQ Magazine, Issue No. 186, September/October 2014, National Fire Sprinkler Association
Victoria Valentine, PE, FSFPE, is the director of engineering and technical services at the American Fire Sprinkler Association. She is a licensed engineer and a Fellow in the Society of Fire Protection Engineers who has expertise with fire sprinkler systems and earthquake protection for mechanical systems. She has served on the NFPA Technical Committee for Hanging and Bracing of Water-Based Fire Protection Systems for more than 20 years and the ASCE 7: Minimum Design Loads and Associated Criteria for Buildings and Other Structures Committee since 2006.