Earthquake

About the program

Reference: NS-EN 1998-1:2004+A1:2013+NA:2021 – NA.3.2.1(5)

This tool verifies the omission criteria to determine whether further earthquake calculations are required according to clause NA.3.2.1(5) in NS-EN 1998-1:2004+A1:2013+NA:2021.

For structures in seismic class I–IIIa, verification against seismic action per NS-EN 1998 may be omitted when any of the following criteria is satisfied:

1. Structures in seismic class I.
2. Structures on ground types A–E where the ground acceleration including amplification satisfies agS ≤ 0.50 m/s².
3. Structures on ground types A–E where the ground acceleration satisfies ag ≤ 0.30 m/s².
4. Structures on ground types A–E with a design working life ≤ 2 years.

Criterion 5 from the omission criteria is not included and is therefore not checked in this tool.

For seismic classes IIIb and IV, verification against seismic action per NS-EN 1998 is always required.

Typical use case: Checking omission criteria for seismic design of structures in seismic class I–IIIa.

Map illustration for earthquake acceleration

Key formulas

Design ground acceleration

ag=γ1⋅agRa_g = \gamma_1 \cdot a_{gR}
γ1\gamma_1Seismic factor
agRa_{gR}Reference peak ground acceleration (PGA)
aga_gDesign ground acceleration

Omission criterion 2

ag⋅S≤0,50  m/s2a_g \cdot S \leq 0{,}50\;\text{m/s}^2
aga_gDesign ground acceleration
SSGround amplification factor

Inputs

  • Seismic class (I–IIIa)
  • Period of use (years)
  • Reference ground acceleration, agR (m/s²)
  • Ground type and amplification factor, S

Outputs

  • Design ground acceleration, ag (m/s²)
  • Ground acceleration incl. amplification, ag · S (m/s²)
  • Satisfied omission criteria (criteria 1–4)
  • Assessment (further calculations required / not required)

Assumptions

  • Simplified method – NA.3.2.1(5) in NS-EN 1998-1:2004+A1:2013+NA:2021
  • Applies to seismic class I–IIIa
  • Ground type A–E (ground types S1 and S2 require special investigations)

Video