otko/examples/ex2c_canti2d_inelastic_fiber_section.py

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2026-09-08 02:12:15 -04:00
"""OpenSees Example 2c. Nonlinear Cantilever Column: Inelastic Fiber Section.
OpenSees Wiki:
https://opensees.berkeley.edu/wiki/index.php?title=OpenSees_Example_2c._Nonlinear_Cantilever_Column:_Inelastic_Uniaxial_Materials_in_Fiber_Section
This example replaces the aggregated uniaxial section of Ex2b with a
fiber section built from inelastic uniaxial materials. The fiber section
couples axial and flexural behavior naturally through the section
integration.
Run from the repository root:
python examples/ex2c_canti2d_inelastic_fiber_section.py
Produces ``examples/ex2c_canti2d_inelastic_fiber_section.osmodel``.
"""
from __future__ import annotations
from pathlib import Path
import math
import sys
if __package__ is None or __package__ == "":
sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "src"))
from otko.core import ( # noqa: E402
Concrete02,
FiberSection,
ForceBeamColumn,
LinearTimeSeries,
NodalLoad,
Node,
PathTimeSeries,
PlainLoadPattern,
Project,
ProjectMeta,
PushoverCase,
RectangularPatch,
Steel02,
StraightLayer,
TransientCase,
StaticCase,
UniformExcitationPattern,
UnitSystem,
)
from otko.services import load_project, save_project # noqa: E402
from otko.services.peer_record import parse_plain_values # noqa: E402
L_COL = 432.0
WEIGHT = 2000.0
H_COL = 60.0
B_COL = 60.0
G_ACCEL = 386.4
P_COL = WEIGHT
MASS = P_COL / G_ACCEL
A_COL = B_COL * H_COL
IZ_COL = (1.0 / 12.0) * B_COL * H_COL**3
COVER_COL = 5.0
NUM_BARS_COL = 5
BAR_AREA_COL = 2.25
FC = -4.0
EC = 57.0 * math.sqrt(-FC * 1000.0)
FC1U = FC
EPS1U = -0.003
FC2U = 0.2 * FC1U
EPS2U = -0.01
LAMBDA = 0.1
FTU = -0.14 * FC1U
ETS = FTU / 0.002
FY = 66.8
ES = 29000.0
BS = 0.01
R0 = 18.0
CR1 = 0.925
CR2 = 0.15
NUM_INT_PTS = 5
N_GRAVITY = 10
GRAVITY_STEP = 1.0 / N_GRAVITY
PUSH_TARGET = 0.01 * L_COL
PUSH_STEP = 0.001 * L_COL
H_LOAD = WEIGHT
GROUND_DT = 0.01
GROUND_FACTOR = 1.0
ANALYSIS_DT = 0.01
ANALYSIS_STEPS = 1000
DAMPING_RATIO = 0.02
_ROOT = Path(__file__).resolve().parent
GROUND_MOTION_FILE = _ROOT / "data" / "BM68elc.acc"
REFERENCE_PUSH_TCL = _ROOT / "data" / "Ex2c.Canti2D.InelasticFiberSection.Push.tcl.txt"
REFERENCE_EQ_TCL = _ROOT / "data" / "Ex2c.Canti2D.InelasticFiberSection.EQ.tcl.txt"
def _ground_motion_values() -> list[float]:
return parse_plain_values(GROUND_MOTION_FILE)
def build_ex2c_canti2d_inelastic_fiber_section() -> Project:
values = _ground_motion_values()
cover_y = H_COL / 2.0
cover_z = B_COL / 2.0
core_y = cover_y - COVER_COL
core_z = cover_z - COVER_COL
return Project(
meta=ProjectMeta(
name="OpenSees Ex 2c - Inelastic Fiber-Section Cantilever",
author="OpenSees Wiki / Silvia Mazzoni & Frank McKenna",
description=(
"Nonlinear cantilever with a fiber section built from "
"Concrete02 and Steel02 uniaxial materials."
),
units=UnitSystem.US_IN_KIP,
),
ndm=2,
ndf=3,
nodes=[
Node(
id=1,
name="Base",
coords=(0.0, 0.0, 0.0),
restraint=(True, True, False, False, False, True),
),
Node(
id=2,
name="Top",
coords=(0.0, L_COL, 0.0),
mass=(MASS, 1.0e-9, 0.0, 0.0, 0.0, 0.0),
),
],
materials=[
Concrete02(
id=1,
name="Cover-Concrete",
fpc=FC1U,
epsc0=EPS1U,
fpcu=FC2U,
epsU=EPS2U,
lambda_=LAMBDA,
ft=FTU,
Ets=ETS,
),
Steel02(
id=2,
name="Rebar-Steel",
Fy=FY,
E0=ES,
b=BS,
R0=R0,
cR1=CR1,
cR2=CR2,
),
],
sections=[
FiberSection(
id=1,
name="RC-Fiber-Section",
patches=[
RectangularPatch(
material_id=1,
n_fib_y=16,
n_fib_z=4,
y_i=-cover_y,
z_i=-cover_z,
y_j=cover_y,
z_j=cover_z,
),
],
layers=[
StraightLayer(
material_id=2,
n_bars=NUM_BARS_COL,
bar_area=BAR_AREA_COL,
y_start=-core_y,
z_start=core_z,
y_end=-core_y,
z_end=-core_z,
),
StraightLayer(
material_id=2,
n_bars=NUM_BARS_COL,
bar_area=BAR_AREA_COL,
y_start=core_y,
z_start=core_z,
y_end=core_y,
z_end=-core_z,
),
],
),
],
elements=[
ForceBeamColumn(
id=1,
name="Column",
nodes=(1, 2),
section_id=1,
integration_points=NUM_INT_PTS,
geom_transf="Linear",
),
],
time_series=[
LinearTimeSeries(id=1, name="Gravity"),
LinearTimeSeries(id=200, name="Lateral"),
PathTimeSeries(
id=400,
name="BM68elc",
dt=GROUND_DT,
factor=GROUND_FACTOR,
values=values,
file_path=str(GROUND_MOTION_FILE.name),
),
],
load_patterns=[
PlainLoadPattern(
id=1,
name="Gravity",
time_series_id=1,
nodal_loads=[
NodalLoad(node_id=2, forces=(0.0, -P_COL, 0.0, 0.0, 0.0, 0.0)),
],
),
PlainLoadPattern(
id=200,
name="Pushover-X",
time_series_id=200,
nodal_loads=[
NodalLoad(node_id=2, forces=(H_LOAD, 0.0, 0.0, 0.0, 0.0, 0.0)),
],
),
UniformExcitationPattern(
id=400,
name="GroundMotion-X",
direction=1,
accel_series_id=400,
),
],
analyses=[
StaticCase(
id=1,
name="Gravity",
pattern_ids=[1],
n_steps=N_GRAVITY,
load_factor_increment=GRAVITY_STEP,
system="BandGeneral",
constraints="Plain",
integrator="LoadControl",
algorithm="Newton",
test="NormDispIncr",
tolerance=1e-8,
max_iter=6,
),
PushoverCase(
id=2,
name="Push",
preload_case_ids=[1],
pattern_ids=[200],
control_node=2,
control_dof=1,
target_disp=PUSH_TARGET,
step_size=PUSH_STEP,
base_nodes=[1],
system="BandGeneral",
constraints="Plain",
algorithm="Newton",
test="EnergyIncr",
tolerance=1e-8,
max_iter=6,
),
TransientCase(
id=3,
name="Earthquake",
preload_case_ids=[1],
pattern_ids=[400],
dt=ANALYSIS_DT,
n_steps=ANALYSIS_STEPS,
system="SparseGeneral",
constraints="Transformation",
integrator="Newmark",
integrator_params=(0.5, 0.25),
algorithm="ModifiedNewton",
test="EnergyIncr",
tolerance=1e-8,
max_iter=10,
rayleigh_mode1_damping=DAMPING_RATIO,
),
],
)
def main() -> None:
project = build_ex2c_canti2d_inelastic_fiber_section()
project.validate_references()
gm = next(ts for ts in project.time_series if ts.id == 400)
print(f"Built '{project.meta.name}'")
print(
f" LCol={L_COL}, ACol={A_COL:.1f}, Iz={IZ_COL:.1f}, "
f"bars/layer={NUM_BARS_COL}, bar area={BAR_AREA_COL}"
)
print(f" Gravity + pushover + earthquake cases: {len(project.analyses)}")
print(f" Ground motion file: {GROUND_MOTION_FILE.name}")
print(f" Reference Tcls: {REFERENCE_PUSH_TCL.name}, {REFERENCE_EQ_TCL.name}")
print(f" Record points: {len(gm.values)}, dt = {GROUND_DT}s, factor = {GROUND_FACTOR}")
out_path = Path(__file__).with_suffix(".osmodel")
save_project(project, out_path)
print(f"Saved -> {out_path}")
restored = load_project(out_path)
restored.validate_references()
assert restored.model_dump(by_alias=True) == project.model_dump(by_alias=True)
print("Round-trip OK.")
if __name__ == "__main__":
main()