232 lines
8.3 KiB
Python
232 lines
8.3 KiB
Python
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"""RC Frame Gravity Analysis — OpenSees Examples Manual, Example 3.
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Single-bay, single-storey RC portal frame under gravity (two 180-kip
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nodal loads on top joints). Columns are nonlinear forceBeamColumn
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elements with the fibre section from the Moment-Curvature example;
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the beam is an elasticBeamColumn with stiffness (A, E, Iz) =
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(360, 4030, 8640) — matching the Tcl reference at:
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https://opensees.berkeley.edu/wiki/index.php?title=RC_Portal_Frame
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Model (kip-in-ksi):
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node 3 ─────── elasticBeam 3 ─────── node 4
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│ │
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forceBC 1 forceBC 2
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│ │
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node 1 node 2
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(fixed) (fixed)
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Width 360", height 144", columns fibre-section RC (Concrete01 +
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Steel01). Load pattern: 180 kip ↓ at each top node, Linear time series,
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LoadControl 0.1 × 10 steps = full gravity.
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Expected terminal state (nodes 3 & 4): Uy ≈ -0.0203 in, Ux ≈ 0,
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column axial force ≈ 180 kip compression.
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"""
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from __future__ import annotations
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from pathlib import Path
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from otko.core import (
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Concrete01,
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CoordinateGridSystem,
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ElasticBeamColumn,
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ElasticSection,
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FiberSection,
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ForceBeamColumn,
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GridSystem,
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LinearTimeSeries,
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NodalLoad,
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Node,
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PlainLoadPattern,
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Project,
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ProjectMeta,
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RectangularPatch,
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StaticCase,
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Steel01,
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StraightLayer,
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UnitSystem,
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make_grid_lines,
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)
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from otko.services import load_project, save_project
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# Frame geometry (inches).
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WIDTH = 360.0
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HEIGHT = 144.0
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# Column section parameters (same as Moment-Curvature example).
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COL_WIDTH = 15.0
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COL_DEPTH = 24.0
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COVER = 1.5
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AS_BAR = 0.60
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# Material properties (kip, in, ksi).
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CONC_CORE_FPC = -6.0
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CONC_COVER_FPC = -5.0
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STEEL_FY = 60.0
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# Steel Young's modulus: 30000 ksi (matches OpenSees Wiki, which sources
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# the MK example's $E = 30000). Some Tcl reprints show 3000 — that's a
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# typo; 3000 gives Uy ≈ -0.0203 instead of the reference -0.01837.
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STEEL_E = 30000.0
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STEEL_B = 0.01
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# Beam elastic properties.
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BEAM_A = 360.0
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BEAM_E = 4030.0
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BEAM_IZ = 8640.0
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# Gravity load.
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P_LOAD = 180.0 # kip, pointing -Y (compression on columns)
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def build_rc_frame_gravity() -> Project:
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y1 = COL_DEPTH / 2.0 # 12
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z1 = COL_WIDTH / 2.0 # 7.5
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return Project(
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meta=ProjectMeta(
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name="RC Frame Gravity (OpenSees Ex 3)",
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author="OpenSees Examples Manual",
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description=(
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"1-bay 1-storey portal frame, nonlinear fibre columns + "
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"elastic beam, 10-step LoadControl gravity pushdown."
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),
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units=UnitSystem.US_IN_KIP,
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),
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ndm=2, ndf=3,
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coord_systems=[
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CoordinateGridSystem(
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name="Global",
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grid=GridSystem(
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x_grid_lines=make_grid_lines("X", [0.0, WIDTH]),
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y_grid_lines=make_grid_lines("Y", [0.0, HEIGHT]),
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z_grid_lines=make_grid_lines("Z", [0.0]),
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),
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),
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],
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nodes=[
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Node(id=1, name="Base-L",
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coords=(0.0, 0.0, 0.0),
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restraint=(True, True, False, False, False, True)),
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Node(id=2, name="Base-R",
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coords=(WIDTH, 0.0, 0.0),
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restraint=(True, True, False, False, False, True)),
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Node(id=3, name="Top-L", coords=(0.0, HEIGHT, 0.0)),
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Node(id=4, name="Top-R", coords=(WIDTH, HEIGHT, 0.0)),
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],
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materials=[
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Concrete01(id=1, name="Core-Conc",
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fpc=CONC_CORE_FPC, epsc0=-0.004,
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fpcu=-5.0, epsU=-0.014),
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Concrete01(id=2, name="Cover-Conc",
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fpc=CONC_COVER_FPC, epsc0=-0.002,
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fpcu=0.0, epsU=-0.006),
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Steel01(id=3, name="Steel-60",
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Fy=STEEL_FY, E0=STEEL_E, b=STEEL_B),
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],
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sections=[
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# Fibre section for the columns (MK recipe).
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FiberSection(
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id=1, name="RC-Col",
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patches=[
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RectangularPatch(
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material_id=1, n_fib_y=10, n_fib_z=1,
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y_i=COVER - y1, z_i=COVER - z1,
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y_j=y1 - COVER, z_j=z1 - COVER,
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),
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RectangularPatch(
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material_id=2, n_fib_y=10, n_fib_z=1,
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y_i=-y1, z_i=z1 - COVER,
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y_j=y1, z_j=z1,
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),
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RectangularPatch(
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material_id=2, n_fib_y=10, n_fib_z=1,
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y_i=-y1, z_i=-z1,
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y_j=y1, z_j=COVER - z1,
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),
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RectangularPatch(
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material_id=2, n_fib_y=2, n_fib_z=1,
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y_i=-y1, z_i=COVER - z1,
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y_j=COVER - y1, z_j=z1 - COVER,
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),
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RectangularPatch(
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material_id=2, n_fib_y=2, n_fib_z=1,
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y_i=y1 - COVER, z_i=COVER - z1,
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y_j=y1, z_j=z1 - COVER,
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),
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],
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layers=[
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StraightLayer(
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material_id=3, n_bars=3, bar_area=AS_BAR,
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y_start=y1 - COVER, z_start=z1 - COVER,
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y_end=y1 - COVER, z_end=COVER - z1,
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),
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StraightLayer(
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material_id=3, n_bars=2, bar_area=AS_BAR,
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y_start=0.0, z_start=z1 - COVER,
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y_end=0.0, z_end=COVER - z1,
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),
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StraightLayer(
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material_id=3, n_bars=3, bar_area=AS_BAR,
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y_start=COVER - y1, z_start=z1 - COVER,
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y_end=COVER - y1, z_end=COVER - z1,
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),
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],
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),
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# Elastic section for the beam.
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ElasticSection(
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id=2, name="Beam",
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E=BEAM_E, A=BEAM_A, Iz=BEAM_IZ,
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Iy=BEAM_IZ, G=1500.0, J=1.0, # placeholders for 3D round-trip
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),
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],
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elements=[
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# Columns — fibre-section forceBeamColumn.
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ForceBeamColumn(id=1, name="Col-L",
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nodes=(1, 3), section_id=1,
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integration_points=5, geom_transf="Linear"),
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ForceBeamColumn(id=2, name="Col-R",
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nodes=(2, 4), section_id=1,
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integration_points=5, geom_transf="Linear"),
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# Beam — elastic.
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ElasticBeamColumn(id=3, name="Beam",
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nodes=(3, 4), section_id=2,
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geom_transf="Linear"),
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],
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time_series=[LinearTimeSeries(id=1, name="Gravity")],
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load_patterns=[PlainLoadPattern(
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id=1, name="Gravity", time_series_id=1,
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nodal_loads=[
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NodalLoad(node_id=3, forces=(0, -P_LOAD, 0, 0, 0, 0)),
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NodalLoad(node_id=4, forces=(0, -P_LOAD, 0, 0, 0, 0)),
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],
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)],
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analyses=[StaticCase(
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id=1, name="Gravity",
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pattern_ids=[1],
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n_steps=10, load_factor_increment=0.1,
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system="BandGeneral", constraints="Transformation",
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integrator="LoadControl", algorithm="Newton",
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test="NormDispIncr", tolerance=1e-12, max_iter=10,
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)],
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)
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def main() -> None:
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project = build_rc_frame_gravity()
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project.validate_references()
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print(f"Built '{project.meta.name}'")
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print(f" ndm={project.ndm}, ndf={project.ndf}, units={project.meta.units.value}")
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print(f" Frame: {WIDTH}in x {HEIGHT}in, P = -{P_LOAD} kip at each top node")
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out_path = Path(__file__).with_suffix(".osmodel")
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save_project(project, out_path)
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print(f"Saved -> {out_path}")
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restored = load_project(out_path)
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restored.validate_references()
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assert restored.model_dump(by_alias=True) == project.model_dump(by_alias=True)
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print("Round-trip OK.")
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if __name__ == "__main__":
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main()
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