Earthquake Load Design for DoD Installations Outside the U.S.
December 9, 2024
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Implications of Updated Seismic Parameters on Design and Construction Costs
By Marvin W. Mestanza, SE | Senior Engineer, Structural Engineering, Honolulu
The updated seismic ground motion parameters in UFC 3-301-01, Structural Engineering (Change 2, 4 September 2024) apply to Department of Defense (DoD) installations outside the United States. The updated values translate to increased seismic design forces for most DoD projects in Japan.
Background
Before Change 2 to UFC 3-301-01, seismic design parameters were based on mid-1990s approximations. In 2021, the DoD, along with the Department of State, contracted the Global Earthquake Model (GEM), a non-profit foundation, to develop ground motion parameters for their overseas installations. The new seismic parameters are based on the GEM Global Mosaic of Seismic Hazard Models, which blends several ground motion models to compute the new seismic parameters.
Most new DoD buildings in Japan using the seismic provisions in ASCE 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, will see increased design seismic forces due to the new parameters. The same applies to seismic evaluations of existing buildings using the procedures and acceptance criteria in ASCE 41-17, Seismic Evaluation and Retrofit of Existing Buildings. The increase varies from moderate to significant, depending on the DoD installation.
Key Points
As an example, this table shows the old values, new values, and percentage increases in the seismic parameters for Camp Zama in Japan.
The new accelerations at short periods at Camp Zama for hazard levels BSE-1E and BSE-2E in ASCE 41-17 are nearly double the old values. This means that the seismic forces used to evaluate an existing building using ASCE 41-17 will be almost double what they would have been before September 2024. New buildings at Camp Zama will need to be designed for seismic demands that are 35 percent greater than previously required.
Most of the DoD installations in Japan will experience similar changes in seismic parameters, as shown in the table for Camp Zama. Many structures on DoD bases in Japan are constructed with reinforced concrete, and the new seismic parameters are likely to increase construction costs. Some existing buildings might have met the acceptance criteria for a tier 3 analysis conforming to ASCE 41-17, without structural retrofits, prior to September 2024. These same buildings will most likely now require structural retrofits to meet the acceptance criteria in ASCE 41-17.
Summary and Resources
As outlined in UFC 3-301-01 (Change 2, 4 September 2024), the new ground motion parameters for DoD installations outside the United States have the potential to significantly increase costs at some locations. Seismic parameters for locations in the United States and its territories can be determined using the structural load data tool hosted on the Whole Building Design Guide website.
Refer to the USGS Web Service Page for locations not provided in the structural load data tool. For the US Army Corp of Engineers Engineering and Construction Bulletin, which provides guidance for applying the new seismic parameters, visit the Whole Building Design Guide website.
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