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Eurocode 1 module: ec1

Overview

The ec1 module provides tools for EN 1991 (Actions on Structures). It covers load type definitions, force representations, wind and snow sub-modules, and the full EN 1990 load combination engine.

Load combinations

LoadType (enum)

Classifies an individual load for combination purposes.

Member Value Description
PERMANENT 0 Self-weight, superimposed dead load
LIVE 1 Imposed loads (occupancy)
WIND 2 Wind action
SNOW 3 Snow load
EARTHQUAKE 4 Seismic action
TEMPERATURE 5 Thermal action
FIRE 6 Fire action
ACCIDENTAL 7 Other accidental actions
OTHER 8 —

CombinationType (enum)

Member Description
ULS Ultimate Limit State (EN 1990 Eq. 6.10)
ALS Accidental Limit State
FLS Fatigue Limit State
SLS_K SLS characteristic combination
SLS_FR SLS frequent combination
SLS_QP SLS quasi-permanent combination

Load (dataclass)

Load(name, load_type, gamma_fav, gamma_unf, psi0, psi1, psi2, incombo=True)

A load carries its partial factors (favourable and unfavourable effect, EN 1990 Table A1.2) and its combination coefficients; it does not carry a value. incombo=False leaves it out of the combinations.

Loads and the combinations

from eurocodepy.ec1 import Load, LoadType, Loads

loads = Loads()
#                  name  type                 γ fav  γ unf  ψ0   ψ1   ψ2
loads.add(Load("G", LoadType.PERMANENT, 1.0, 1.35, 0.0, 0.0, 0.0))
loads.add(Load("Q", LoadType.LIVE,      0.0, 1.50, 0.7, 0.5, 0.3))
loads.add(Load("W", LoadType.WIND,      0.0, 1.50, 0.6, 0.2, 0.0))

values = {"G": 20.0, "Q": 8.0, "W": 4.0}                 # characteristic values [kN/m²]

# ULS (EN 1990 Eq. 6.10): a dict {name: LoadCombination}; factors = {load name: (Load, factor)}
for name, combo in loads.get_ULS_combos().items():
    total = sum(factor * values[k] for k, (_, factor) in combo.factors.items())
    print(f"{name:34s} {total:7.2f}")

# SLS characteristic, frequent and quasi-permanent
for name, combo in loads.get_SLS_combos().items():
    print(name)

get_ULS_combos() and get_SLS_combos() return a dictionary {name: LoadCombination}. A LoadCombination has name, type (a CombinationType) and factors, a dictionary {load name: (Load, factor)}. LoadCombinations is a container of LoadCombination objects (add, remove, iteration).

Force representations

Class Description
BaseForce Abstract base class
PlaneForce In-plane forces (Nx, Ny, Nxy)
ShellForce Shell resultants (n_xx, n_yy, n_xy, m_xx, m_yy, m_xy, v_xz, v_yz)
SlabForce Slab resultants (m_xx, m_yy, m_xy, v_xz, v_yz)
FrameForce 1-D frame member forces (n_x, v_y, v_z, m_y, m_z, t_x) 
from eurocodepy.ec1 import ShellForce
f = ShellForce(n_xx=100.0, m_xx=20.0)     # kN, m by default: the unit system `u`
f.forces.shape, f.n_cases                 # (8, 1), 1

Sub-modules

ec1.wind

Functions of EN 1991-1-4 (4.2 to 4.5): v_b, c_r, c_o, s_coef, v_m, I_v, v_p, q_p. Heights and roughness lengths in m, velocities in m/s, pressures in N/m².

from eurocodepy.ec1 import wind

vb = wind.v_b(27.0)                                  # vb,0 = 27 m/s, cseason = cdir = 1
cr = wind.c_r(z=10, z_min=2, z_0=0.05, z_0II=0.05)   # terrain category II
co = wind.c_o(z=10)                                  # flat terrain
vm = wind.v_m(10, vb, cr, co)                        # mean wind velocity
qp = wind.q_p(10, vb, 2, 0.05, cr, co)               # peak velocity pressure [N/m²]

ec1.snow

Placeholder: the snow loads of EN 1991-1-3 are not implemented yet.

Compliance

All combination logic follows EN 1990:2002 and its amendments.

Further reading