Seismic Design: Why Site Investigations Matter More Than Many Realize
When people think about seismic design, they usually picture regions such as Kamchatka or the Caucasus. However, according to the Russian Main Department of State Expert Review (Glavgosexpertiza), 15–30% of the country's territory requires seismic effects to be considered during structural design.
Glavgosexpertiza has recently issued guidance explaining how to correctly determine the design seismicity of a construction site. Here are the key points.
What should you know?
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If the regulatory seismicity of an area is 6 points or higher (on the adopted seismic intensity scale), a seismic hazard assessment is mandatory.
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For standard-risk buildings and structures, designers may rely on the General Seismic Zoning (GSZ) maps.
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However, this approach is not sufficient for hazardous, technically complex, or unique projects.
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Such facilities require either a Refined Seismic Hazard Assessment (RSHA) or Detailed Seismic Zoning (DSZ), including field investigations and specialised engineering analyses.
Why can't archived data be used?
According to Glavgosexpertiza, one of the most common mistakes is omitting field seismic surveys.
Relying on outdated reports or standard soil classification tables instead of conducting actual site investigations does not provide a reliable basis for determining the site's design seismicity. As a result, such engineering reports are frequently returned for revision during the state expert review process.
Moreover, in one case examined by Glavgosexpertiza, new field investigations changed the calculated seismicity of the site by almost one intensity point, requiring a complete revision of the project's structural design.
The most common mistakes
According to Glavgosexpertiza, expert reviewers most frequently identify:
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Failure to perform a Refined Seismic Hazard Assessment (RSHA) for high-responsibility projects.
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Errors in determining soil properties and developing the site's seismic ground model.
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Deficiencies in preparing seismic microzonation maps.
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Incomplete terms of reference for engineering and geological investigations.
Why does it matter?
Design seismicity affects far more than the outcome of the state expert review.
It directly influences structural design solutions, foundation design parameters, construction costs, and, ultimately, the safety and long-term performance of the completed facility.
Comprehensive engineering site investigations enable designers to make informed engineering decisions before construction begins.
Source: Glavgosexpertiza (Zen)
