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Eurocode 8 module: ec8

Overview

The ec8 module provides tools for seismic design according to EN 1998-1. It generates elastic and design response spectra, retrieves national annex parameters for both the standard Eurocode and the Portuguese National Annex, and exports spectra to CSV.

Response spectra — ec8.spectrum

Accelerations are in m/s² (a_g, and the ordinates of the spectra); periods in s.

get_spec_params

Returns the spectrum parameters (S, a_g, T_B, T_C, T_D) for a locale, code, importance class, soil type and seismic zone. a_g = a_gR·γI; S is interpolated between S_max and S_min with a_g.

from eurocodepy.ec8 import get_spec_params

s_val, a_g, t_b, t_c, t_d = get_spec_params(
    locale="PT",        # "EU" (CEN) or "PT" (Portuguese National Annex)
    code="PT1",         # see the table below
    class_imp="II",     # importance class: I, II, III, IV
    soil="C",           # soil type: A, B, C, D, E
    zone="1_2",         # seismic zone (code-dependent)
)

Available codes

locale code Description
EU CEN_1 Standard Eurocode type 1 spectrum
EU CEN_2 Standard Eurocode type 2 spectrum
PT PT1 Portuguese NA — type 1 (continental Portugal)
PT PT2 Portuguese NA — type 2
PT PTA Portuguese NA — Azores

Seismic zones

  • PT1: 1_1, 1_2, 1_3, 1_4, 1_5, 1_6
  • PT2 / PTA: 2_1, 2_2, 2_3, 2_4, 2_5
  • CEN_1 / CEN_2: .1g, .2g, … .9g, 1_0g (the reference acceleration as a fraction of g)

get_spectrum_ec8

Builds the horizontal design spectrum as a pandas.DataFrame with columns period and value.

from eurocodepy.ec8 import get_spectrum_ec8

spec = get_spectrum_ec8(
    locale="PT",
    code="PT1",
    imp_class="II",
    soil="C",
    zone="1_2",
    behaviour=3.0,   # behaviour factor q
)
spec.columns.tolist()       # ['period', 'value']
spec["value"].max()         # largest design ordinate [m/s²]

get_spectrum_user and get_elastic_spectrum_user

Spectra from arbitrary parameters, without a National Annex entry.

from eurocodepy.ec8 import get_spectrum_user, get_elastic_spectrum_user

# a_g [m/s²], S, q, T_B, T_C, T_D
design = get_spectrum_user(a_g=2.0, s_val=1.15, q=4.0, t_b=0.1, t_c=0.6, t_d=2.0)
elastic = get_elastic_spectrum_user(a_g=2.0, s_val=1.15, t_b=0.1, t_c=0.6, t_d=2.0, damping=5.0)

calc_spectrum, calc_elastic_spectrum, damping_correction

Ordinates of one period, from already-extracted parameters (EN 1998-1, Eqs. 3.2 to 3.5 and 3.13 to 3.16).

from eurocodepy.ec8 import calc_spectrum, calc_elastic_spectrum, damping_correction

sd = calc_spectrum(0.3, a_g=2.0, s_val=1.15, q=3.0, t_b=0.1, t_c=0.6, t_d=2.0)   # design
se = calc_elastic_spectrum(0.3, 2.0, 1.15, 0.1, 0.6, 2.0)                       # elastic, 5 % damping
eta = damping_correction(5.0)                                                    # 1.0

get_spectrum_parameters(code, coef_imp, soil, zone) is the same lookup as get_spec_params with the tables inside the function (codes CEN-1, CEN-2, PT-1, PT-2, PT-A, hyphenated); prefer get_spec_params.

draw_spectrum_ec8

Plots the spectrum with matplotlib.

from eurocodepy.ec8 import draw_spectrum_ec8

draw_spectrum_ec8(spec, show=False, save=True, filename="spectrum.png")

write_spectrum_ec8

Exports the spectrum to a text file (two columns, period and value).

from eurocodepy.ec8 import write_spectrum_ec8

write_spectrum_ec8(spec, filename="spectrum_PT1_II_C_1_2.csv", separator=",")

Compliance

Calculations follow EN 1998-1:2004 and the Portuguese National Annex (NP EN 1998-1).

Further reading