YAML input reference¶

A GenSec YAML file has four top-level blocks: materials, section, demands (optional), and combinations (optional). An output block controls which post-processing artefacts are generated.

`materials` block¶

A dictionary of named material definitions. Each key becomes the identifier used in the section block to assign materials to the bulk concrete or to individual rebar layers.

Concrete — direct parameters¶

materials:
  concrete_1:
    type: concrete_ec2_gen1_custom
    fck: 25.0             # characteristic cylinder strength [MPa]
    gamma_c: 1.5          # partial safety factor (default 1.5)
    alpha_cc: 0.85        # long-term coefficient (default 0.85)
    n_parabola: 2.0       # parabolic exponent (default 2.0)
    eps_c2: -0.002        # peak-stress strain (default -0.002)
    eps_cu2: -0.0035      # ultimate strain (default -0.0035)
    fct: 0.0              # tensile strength [MPa] (default 0 = no tension)
    Ec: 0.0               # elastic modulus [MPa] for tension (default 0)

Only fck is required; all other fields have the defaults shown above. The legacy type name concrete is accepted as an alias.

The design compressive strength is computed internally as:

\[f_{cd} = \alpha_{cc} \, \frac{f_{ck}}{\gamma_c}\]

When both fct and Ec are positive, a linear tension branch is activated up to the cracking strain \(\varepsilon_{ct} = f_{ct}/E_c\). See Constitutive laws for the full piecewise definition.

Concrete — from EC2 class¶

materials:
  concrete_1:
    type: concrete_ec2_gen1
    class: C30/37          # EC2 class name (C12/15 … C90/105)
    ls: F                  # limit state: 'F' fundamental, 'A' accidental
    loadtype: slow         # 'slow' or 'fast' (default 'slow')
    TypeConc: R            # 'R' rapid, 'N' normal, 'S' slow hardening
    enable_tension: false  # activate linear tension branch (default false)
    tension_fct: fctd      # which fct: 'fctd', 'fctm', or 'fctk'

The legacy type name concrete_ec2 is accepted as an alias.

All Table 3.1 parameters (\(f_{cm}\), \(f_{ctm}\), \(E_{cm}\), \(\varepsilon_{c2}\), \(\varepsilon_{cu2}\), \(n\), etc.) are computed automatically by the ec2_properties module.

When enable_tension: true, the elastic modulus \(E_{cm}\) and the chosen tensile strength (\(f_{ctd}\), \(f_{ctm}\), or \(f_{ctk,0.05}\)) are extracted from the EC2 property object and passed to the Concrete constructor. The tension_fct field controls which value is used:

Note

Only the French National Annex (NF EN 1992-1-1/NA) is implemented. Other national annexes may be added in the future.

Reinforcing steel¶

materials:
  steel_1:
    type: steel
    fyk: 450.0               # characteristic yield strength [MPa]
    gamma_s: 1.15            # partial safety factor (default 1.15)
    Es: 200000               # Young's modulus [MPa] (default 200000)
    k_hardening: 1.0         # ft/fy ratio (default 1.0 = perfectly plastic)
    eps_su: 0.01             # ultimate strain (default 0.01)
    works_in_compression: true  # if false, σ = 0 for ε < 0

Only fyk is required.

Structural steel (EN 10025-2)¶

materials:
  steel_plate:
    type: steel_en10025
    grade: S355              # S235, S275, or S355
    t: 20                    # plate thickness [mm]
    gamma_s: 1.0             # partial safety factor (default 1.0)

Yield and ultimate strengths are automatically adjusted for plate thickness according to NF EN 10025-2 Table 7.

Tabulated material¶

materials:
  cfrp:
    type: tabulated
    name: CFRP_sheet
    strains:  [0.0, 0.017]
    stresses: [0.0, 2800.0]

Piecewise-linear interpolation between data points. Strains outside the table range produce zero stress (material failure). The strains array must be strictly increasing.

`section` block¶

Two formats are supported: the legacy rectangular format (backward compatible) and the generic section format (arbitrary polygons).

Legacy rectangular section¶

section:
  B: 300                   # width [mm]
  H: 600                   # height [mm]
  bulk_material: concrete_1
  n_fibers_y: 50            # fiber count along height
  n_fibers_x: 20            # explicit x resolution (optional)
  rebars:
    - y: 40
      As: 942.5
      material: steel_1
      n_bars: 3             # optional, for reporting
      diameter: 20          # optional, for reporting [mm]
    - y: 560
      As: 942.5
      material: steel_1

The origin is at the bottom-left corner of the bounding box.

Grid resolution is controlled by n_fibers_y, which sets the mesh size \(s = H / n_y\). When n_fibers_x is omitted or set to 1, an isotropic grid is used: the x-resolution is derived from the same mesh size, giving approximately square cells. For example, B=300, H=600, n_fibers_y=50 produces mesh_size=12 and n_fibers_x=25, for a total of 1250 fibers.

Set n_fibers_x explicitly to override the x-resolution (e.g., n_fibers_x: 30 for a 30×50 grid).

Note

RectSection is internally a convenience wrapper around GenericSection with a rectangular polygon. All attributes (n_fibers_x, dx, polygon, etc.) are available directly on the returned object.

Generic section — parametric shapes¶

section:
  shape: <shape_name>
  params:
    <shape-specific parameters>
  bulk_material: concrete_1
  mesh_size: 15             # target fiber edge length [mm]
  mesh_method: grid         # 'grid' (default) or 'triangle'
  rebars:
    - y: 40
      x: 150               # x required for 2D shapes
      As: 314.16
      material: steel_1

Available shapes and their parameters:

`shape`	Required `params`
`rect`	`B`, `H`
`circle`	`D` (diameter), `resolution` (polygon vertices)
`annulus`	`D_ext`, `D_int`, `resolution`
`tee`	`bf`, `hf`, `bw`, `hw`
`inv_tee`	`bf`, `hf`, `bw`, `hw`
`h_section`	`bf`, `tf`, `bw`, `hw`
`box`	`B`, `H`, `tw`, `tf`
`single_tee`	`bf`, `hf`, `bw`, `hw`, `hw2`
`double_tee`	`bf`, `hf`, `bw`, `hw`, `hw2`, `s`

All dimensions in millimetres. See primitives for the full parameter description of each factory function.

Generic section — custom polygon¶

section:
  shape: custom
  params:
    exterior:
      - [0, 0]
      - [400, 0]
      - [400, 700]
      - [0, 700]
    holes:
      - - [80, 80]
        - [320, 80]
        - [320, 620]
        - [80, 620]
  bulk_material: concrete_1
  mesh_size: 12

Vertex coordinates are [x, y] in millimetres. The holes list is optional; each hole is a list of vertices defining an interior ring.

Meshing methods¶

grid (default): rectangular grid clipped to the polygon boundary. Fast and robust. Resolution is controlled by mesh_size.
triangle: constrained Delaunay triangulation via the triangle library. Better suited for curved boundaries (circles, annuli). Requires triangle to be installed.

Rebar fields¶

Each rebar entry supports:

Either As or diameter must be provided. If only diameter is given, n_bars defaults to 1.

`demands` block¶

A list of individual load demands to verify against the resistance domain.

demands:
  - name: Gravity
    N_kN: -1500
    Mx_kNm: 200
    My_kNm: 0
  - name: Seismic_X
    N_kN: -1200
    Mx_kNm: 280
    My_kNm: 0

Units: N_kN in kN, Mx_kNm and My_kNm in kN·m.

Both Mx_kNm and My_kNm are required. For uniaxial analysis, set My_kNm: 0. The legacy field M_kNm is accepted as an alias for Mx_kNm with My_kNm = 0.

`combinations` block¶

Groups of load triples under a single name. Typical use case: the same section is used on multiple columns in a building, each with its own internal forces.

combinations:
  - name: Seismic_X_envelope
    demands:
      - {N_kN: -1800, Mx_kNm: 180, My_kNm: 30}
      - {N_kN: -1500, Mx_kNm: 250, My_kNm: 45}
      - {N_kN: -1200, Mx_kNm: 300, My_kNm: 20}

GenSec reports the utilization ratio \(\eta\) for every triple, plus \(\eta_{\max}\) per combination.

`output` block¶

Controls optional post-processing. All fields are optional and default to the values shown below.

output:
  # ── Utilization ratio flags ──
  eta_3D: true               # 3D ray on N-Mx-My hull (default: true)
  eta_2D: false              # 2D ray on Mx-My contour at fixed N (default: false)
  eta_path: true             # 3D ray for staged combinations (default: true)
  eta_path_2D: false         # 2D ray for staged combinations (default: false)
  delta_N_tol: 0.03          # ΔN tolerance for eta_path_2D (default: 0.03)

  # ── Domain generation ──
  generate_mx_my: false      # produce Mx-My contour diagrams (default: false)
  generate_3d_surface: false # produce 3-D resistance surface (default: false)
  n_angles_mx_my: 144        # angular resolution for Mx-My (default: 144)

  # ── Moment-curvature and ductility ──
  generate_moment_curvature: true      # M-χ diagrams per N level (default: true)
  generate_polar_ductility: true       # polar ductility plot (default: true)
  generate_3d_moment_curvature: true   # 3D M-χ-N surface (default: true)

  # ── N-level strategy ──
  n_levels_mode: demands     # "demands", "auto", or "explicit" (default: "demands")
  # n_levels_count: 10       # for "auto" mode
  # n_levels_values: [-3000, -1500, 0]  # for "explicit" mode [kN]

The generate_moment_curvature, generate_polar_ductility, and generate_3d_moment_curvature flags control whether the computationally expensive moment-curvature diagrams and related outputs are produced. Setting all three to false significantly reduces run time for cases where only the resistance domain and demand verification are needed.

Note

When eta_2D is enabled, GenSec generates an Mx-My contour (via generate_mx_my()) for each unique N level encountered in demands, combinations, and envelopes. This can be expensive for many distinct N values. Contours are cached so that the same N level is never computed twice.

For sections where the 3-D domain is 2-D (no My data), eta_2D and eta_path_2D are automatically disabled with an informative message.

YAML input reference¶

materials block¶

Concrete — direct parameters¶

Concrete — from EC2 class¶

Reinforcing steel¶

Structural steel (EN 10025-2)¶

Tabulated material¶

section block¶

Legacy rectangular section¶

Generic section — parametric shapes¶

Generic section — custom polygon¶

Meshing methods¶

Rebar fields¶

demands block¶

combinations block¶

output block¶

`materials` block¶

`section` block¶

`demands` block¶

`combinations` block¶

`output` block¶