Earthquake Engineering Glossary
Analysis Methods
Codes & Standards
- ASCE 41: A U.S. standard for the seismic evaluation and retrofit of existing buildings.
- ASCE 7 (USA): The main U.S. standard for structural loading, including seismic forces.
- ATC-40 / ATC-72: Seminal documents from ATC providing seismic design and analysis guidelines.
- CSA A23.3 (Canada): Canada’s concrete design standard that includes provisions for seismic resistance.
- Eurocode 8 (Europe): The European standard for earthquake-resistant design of buildings and infrastructure.
- FEMA 310: A FEMA guideline for the rapid visual screening and evaluation of existing buildings.
- FEMA 356: A now-superseded guideline for seismic rehabilitation of buildings.
- FEMA E-74: A FEMA publication focused on nonstructural earthquake mitigation.
- FEMA P-58: A guideline from FEMA that supports performance-based seismic design and risk assessment.
- GB 50011 (China): China’s national seismic design code for buildings.
- IBC (International Building Code): The primary U.S. model building code that includes seismic design requirements.
- IS 1893 (India): India’s national standard for earthquake-resistant design of structures.
- Japanese Building Code (Japan): Japan’s structural design standard for earthquakes, among the most advanced globally.
- NBC Canada (Canada): Canada’s National Building Code, including provisions for seismic design.
- NCh 433 (Chile): Chile’s primary building code for seismic design.
- NZS 1170.5 (New Zealand): New Zealand's national standard for earthquake actions in structural design.
- Seismic Design Category (SDC): A classification that tells how strong a building must be against earthquakes.
- SNiP (Russia): The Russian system of building codes, including seismic design standards.
Design Philosophy
- Capacity Design: A design approach that makes sure structures fail in safe, controlled ways.
- Collapse Prevention: A performance level where a structure avoids global collapse but may not be repairable.
- Design Response Spectrum: A curve representing maximum structural responses over a range of periods for a specific ground motion.
- Immediate Occupancy: A performance objective where a structure remains safe and operational after an earthquake.
- Importance Factor: A multiplier in seismic design that adjusts demands based on building use and consequence of failure.
- Life Safety: A performance objective where occupants can safely evacuate after a design-level earthquake.
- Performance-Based Design (PBD): A design approach that targets specific performance goals instead of prescriptive code compliance.
- Redundancy Factor (ρ): A factor that increases seismic design forces for structures lacking load path redundancy.
- Response Modification Factor (R): A code-defined factor that reduces elastic seismic forces to account for inelastic behavior.
- Seismic Isolation: A technique to reduce earthquake force by allowing a building to move independently from the ground.
Geotechnical
- Liquefaction: A geotechnical phenomenon where saturated soil temporarily behaves like a liquid during shaking.
- Site Class: A category that describes how the ground beneath a building affects earthquake shaking.
- Soil-Structure Interaction (SSI): The way a building and the ground it sits on affect each other during shaking.
Seismic Forces
- Base Shear: The total horizontal force at the base of a building during an earthquake.
- Seismic Load: The force that an earthquake applies to a structure.
Structural Behavior
- Brittle Failure: A sudden, catastrophic structural failure without warning.
- Damping Ratio: A measure of how much energy a structure loses during vibration.
- Ductility: The ability of a structure to undergo large deformations without collapsing.
- Hysteresis: The energy loss and deformation pattern observed in cyclic loading.
- Inelastic Deformation: Permanent deformation in a structure beyond its elastic limit.
- Overstrength: The additional strength of a structure beyond what is required by code.
- Plastic Hinge: A zone in a structure where it bends permanently during an earthquake.
- Pounding: When adjacent buildings strike each other during an earthquake.
- Redundancy: Having multiple load paths in a structure to resist earthquake forces.
- Soft Story: A level in a building that is significantly weaker or more flexible than the stories above it.
- Story Drift: The lateral displacement difference between two floors in a building.
- Torsional Irregularity: Uneven twisting of a building during earthquake shaking due to asymmetrical stiffness or mass.
Structural Systems
Seismic Hazard
- Attenuation: The reduction in earthquake wave intensity with distance from the source.
- Fault Rupture: Surface displacement due to movement along a fault during an earthquake.
- Ground Motion Parameters (PGA, PGV, PGD): Quantitative measures of ground shaking intensity during earthquakes.
- Intensity Scale: A measure of earthquake effects at a specific location.
- Magnitude: A measure of the energy released by an earthquake.
- Seismic Hazard: The likelihood of experiencing earthquake effects at a location within a time frame.
- Seismic Risk: The expected consequences of earthquakes, combining hazard, vulnerability, and exposure.
- Site Amplification: The increase in ground motion at the surface due to local soil and geology.
- Spectral Acceleration (Sa): The peak acceleration experienced by a structure with a given period and damping.
- Spectral Displacement (Sd): The maximum displacement of a structure with a given period and damping under seismic loading.
- Surface Wave: Seismic waves that travel along the Earth's surface and typically cause the most damage.