Seismic Regulations and Code Systems
LEVELS OF SEISMIC REGULATIONS
On an international level, there isn’t a standard seismic code that all countries must follow. Different countries share their codes, and other countries can reference those if they want to, but it is up to each country. The main ones that are referenced are:
- IBC/ASCE 7 (United States)
- Eurocode 8 (Europe)
- NZS 1170.5 (New Zealand)
- GB 50011 (China)
- IS 1893 (India)
Enforcement is usually handled at a local or regional level, and how strictly the code is followed depends on the government structure, available resources, and local priorities.
There isn’t a universal international code since earthquake risk varies regionally, site conditions differ, and economic, political, and regulatory systems, as well as historical development, cultural, and social differences, all play a role. A standard code would result in over-designing in regions where earthquakes aren’t prevalent, or under-designing in regions where there are higher-magnitude earthquakes.
ASSUMPTIONS, UNCERTAINTY, AND RISK
Since earthquakes are a hazard that is difficult to predict, there are a lot of unknown factors that play into seismic design, which are reflected in seismic codes. The table lists the assumptions that are in codes, how they attempt to deal with the unknowns, and why national codes differ when they’re based on the same engineering principles.
MAJOR SEISMIC CODES
While seismic codes from different countries are based on the same engineering principles, they still have major differences based on the priorities and experiences of each country.
DESIGN PHILOSOPHY: CODE-BASED vs. PERFORMANCE-BASED
Code-based (prescriptive) design is when engineers follow a set of strict rules that tell them exactly what a building must do to save the most lives during earthquakes. Performance-based design is when engineers can decide how they want the building to behave during different levels of earthquakes. They can design it to stay fully usable, limit damage, or just avoid collapse, depending on the situation. It’s more flexible and focuses on the actual performance of the building, not just following rules.
