otko/examples

Example models

Pre-built .osmodel files plus the Python scripts that generate them. Each one carries the case types the post-processing views need, so you can exercise the GUI without defining materials, sections, loads, and cases by hand.

Files

Model	Nodes	Elements	Cases	Shows
cantilever.osmodel	6	5	Static × 2, Modal	Point + distributed loads, force diagrams, deformed shape, mode shapes
portal_frame.osmodel	4	3	Static, Modal, Transient	All Display features, smallest 3D
space_frame_3d.osmodel	12	16	Static, Modal, Transient (5% damping)	3D rendering, multiple modes, damped EQ time-history
sdof_pushover.osmodel	2	1	Pushover, Modal	Monotonic pushover curve, HystereticMaterial
portal_pushover.osmodel	4	3	Pushover, Modal	Fiber sections, BeamWithHinges, yielding pushover
ex1a_canti2d.osmodel	2	1	Static preload, Pushover, Transient EQ	OpenSees Ex 1a, shared gravity + push + quake
ex1b_portal2d.osmodel	4	3	Static preload, Pushover, Transient EQ	OpenSees Ex 1b elastic portal, distributed gravity
ex2a_canti2d_elastic_element.osmodel	2	1	Static preload, Pushover, Transient EQ	Ex 2a cantilever, dimensions as named parameters
ex2b_canti2d_inelastic_section.osmodel	2	1	Static preload, Pushover, Transient EQ	Ex 2b, aggregated axial+flexure section
ex2c_canti2d_inelastic_fiber_section.osmodel	2	1	Static preload, Pushover, Transient EQ	Ex 2c, fiber section, coupled axial-flexure
ex3_canti2d_elastic_element.osmodel	2	1	Static preload, Pushover, Transient EQ	Ex 3 elastic build, unit-scaled parameters
ex3_canti2d_inelastic_section.osmodel	2	1	Static preload, Pushover, Transient EQ	Ex 3 aggregated-section build
ex3_canti2d_inelastic_fiber_section.osmodel	2	1	Static preload, Pushover, Transient EQ	Ex 3 fiber-section build
ex4_portal2d_elastic_element.osmodel	4	3	Static preload, Pushover, Transient sine	Ex 4 elastic portal, build/analysis split
ex4_portal2d_inelastic_section.osmodel	4	3	Static preload, Pushover, Transient sine	Ex 4 aggregated-section portal
ex4_portal2d_inelastic_fiber_section.osmodel	4	3	Static preload, Pushover, Transient sine	Ex 4 fiber-section portal
ex1a_canti2d_eq.osmodel	2	1	Static preload, Transient EQ	Ex 1a gravity + base excitation only
eigen_two_storey_shear_frame.osmodel	6	6	Modal	equalDOF floor constraints, shear-frame modes
eigen_two_storey_one_bay_frame.osmodel	6	6	Modal	Chopra 10.5 frame, sway modes, no constraints
concrete04_cantilever.osmodel	2	1	Static (gravity), Pushover	Concrete04 fiber section end-to-end

Quick tour

1. Force diagrams — cantilever.osmodel

File → Open → cantilever.osmodel
Analyze → Cases  → run "Tip-Load"
Display → Show Force Diagram → component "M3" → linear moment, max at fixed end (50 kN·m)
                              → component "V2" → constant -10 kN along the whole span
                              → component "N"  → ~zero (no axial load)
                              → component "T"  → ~zero (no torsion → console hint, no diagram)
Display → Show Deformed Shape  → cantilever curve

Load runs along global Y (perpendicular to the beam, horizontal plane). With the default 3D vertical-reference convention that lands on the V2 / M3 pair — the in-plane bending pair.

UDL variant, parabolic moment:

Analyze → Cases → run "Uniform-Load"
Display → Show Force Diagram → M3 → parabolic, max 25 kN·m at fixed end
                              → V2 → linear, max 10 kN at fixed end

2. Mode shapes — space_frame_3d.osmodel

File → Open → space_frame_3d.osmodel
Analyze → Cases  → run "Modal-6"
Display → Animate Mode Shape → mode 1 = X-sway, mode 2 = Y-sway
                             → Play, scrub timeline, change scale

3. Time-history and hysteresis — space_frame_3d.osmodel

File → Open → space_frame_3d.osmodel
Analyze → Cases  → run "EQ-4s"  (~5-10 sec on a modern laptop)
Display → Time-History Plot
   - Node 12 (roof corner) + DOF 1 (X displacement) → "Add trace"
   - Node 9 + DOF 1 → second trace, compare phase
Display → Hysteresis Plot
   - X = Node 12 / DOF 1, Y = Node 12 / DOF 3 → orbit

4. Pushover — sdof_pushover.osmodel

File → Open → sdof_pushover.osmodel
Analyze → Cases → run "Push-X"
Display → Show Pushover Curve
   → linear from origin, then softens through yield

Column stays elastic here. Real nonlinear hinges need BeamWithHinges + fiber sections; the machinery exists, the fiber-section editor is still rough.

5. Nonlinear pushover with fiber hinges — portal_pushover.osmodel

File → Open → portal_pushover.osmodel
Analyze → Cases → run "Push-X"
Display → Show Pushover Curve
   → linear stiffness, then yield plateau as base hinges form
   → peak base shear = concrete crushing + rebar yield

Columns are BeamWithHinges + FiberSections (concrete core, rebar layers) wrapped in a SectionAggregator for torsion.

6. Gravity + time-history chain — ex1a_canti2d_eq.osmodel

File → Open → ex1a_canti2d_eq.osmodel
Analyze → Cases → run "Earthquake"
Display → Time-History Plot
   - Node 2 + DOF 1 (Ux) → tip horizontal response
   - Node 2 + DOF 2 (Uy) → gravity should stay locked

Tiny model, exists for one reason: the standard transient recipe static preload → loadConst reset → UniformExcitation transient against a real ground-motion record in a PathTimeSeries.

7. OpenSees Ex 1a bundle — ex1a_canti2d.osmodel

File → Open → ex1a_canti2d.osmodel
Analyze → Cases → run "Push" or "Earthquake"
Display → Show Pushover Curve / Time-History Plot

Cantilever column with shared gravity preload and both lateral variants. Small benchmark for checking pushover and transient agree on the same geometry.

8. OpenSees Ex 1b bundle — ex1b_portal2d.osmodel

File → Open → ex1b_portal2d.osmodel
Analyze → Cases → run "Push" or "Earthquake"
Display → Show Pushover Curve / Time-History Plot

Elastic portal frame. Gravity comes from a distributed beam load instead of nodal loads, which is the whole point of keeping it around.

9. Ex 2a, parameter-driven — ex2a_canti2d_elastic_element.osmodel

File → Open → ex2a_canti2d_elastic_element.osmodel
Analyze → Cases → run "Push" or "Earthquake"
Display → Show Pushover Curve / Time-History Plot

Same physics as Ex 1a, but dimensions and derived quantities are named parameters instead of literals.

10. Ex 2b, aggregated section — ex2b_canti2d_inelastic_section.osmodel

File → Open → ex2b_canti2d_inelastic_section.osmodel
Analyze → Cases → run "Push" or "Earthquake"
Display → Show Pushover Curve / Time-History Plot

First nonlinear cantilever in the series. Separate axial and flexural uniaxial responses aggregated into one section on a force-based beam-column.

11. Ex 2c, fiber section — ex2c_canti2d_inelastic_fiber_section.osmodel

File → Open → ex2c_canti2d_inelastic_fiber_section.osmodel
Analyze → Cases → run "Push" or "Earthquake"
Display → Show Pushover Curve / Time-History Plot

Ex 2b's fiber counterpart. Coupled axial-flexure with concrete and steel assigned to fibers and rebar layers directly.

12. Ex 3 family — ex3_canti2d_*.osmodel

File → Open → ex3_canti2d_elastic_element.osmodel
Analyze → Cases → run "Push" or "Earthquake"

Same cantilever analyses on three build styles: elastic element, aggregated uniaxial section, fiber section. All unit-scaled.

13. Modal shear building — eigen_two_storey_shear_frame.osmodel

File → Open → eigen_two_storey_shear_frame.osmodel
Analyze → Cases → run "Modal-2"
Display → Animate Mode Shape
   - mode 1 → stories sway in phase
   - mode 2 → stories sway out of phase

Validates modal workflows on a model small enough to check by hand, with equalDOF doing the shear-frame duty.

14. Modal frame, Chopra 10.5 — eigen_two_storey_one_bay_frame.osmodel

File → Open → eigen_two_storey_one_bay_frame.osmodel
Analyze → Cases → run "Modal-2"
Display → Animate Mode Shape
   - mode 1 → in-phase sway of both stories
   - mode 2 → top story reverses against the first

Companion to the shear building above. Ordinary beam-column behavior, no multi-point constraints.

15. Ex 4 portal family — ex4_portal2d_*.osmodel

File → Open → ex4_portal2d_elastic_element.osmodel
Analyze → Cases → run "Push" or "Sine-Uniform"
Display → Show Pushover Curve / Time-History Plot

Keeps the OpenSees split between model-building and analysis files, recast as project variants. Covers pinned-base sway, distributed girder gravity, and support-motion dynamics without an external quake file. The fiber transient is kept as a nonlinear stress test — it may stop early and still produce usable partial histories.

Regenerating the .osmodel files

Scripts are the source of truth, .osmodel files are build artifacts checked in for convenience. Change a script, rerun it:

python examples/cantilever.py
python examples/portal_frame.py
python examples/space_frame_3d.py
python examples/sdof_pushover.py
python examples/portal_pushover.py
python examples/ex1a_canti2d.py
python examples/ex1b_portal2d.py
python examples/ex2a_canti2d_elastic_element.py
python examples/ex1a_canti2d_eq.py
python examples/ex2b_canti2d_inelastic_section.py
python examples/ex2c_canti2d_inelastic_fiber_section.py
python examples/ex3_canti2d_elastic_element.py
python examples/ex3_canti2d_inelastic_section.py
python examples/ex3_canti2d_inelastic_fiber_section.py
python examples/ex4_portal2d_elastic_element.py
python examples/ex4_portal2d_inelastic_section.py
python examples/ex4_portal2d_inelastic_fiber_section.py
python examples/eigen_two_storey_shear_frame.py
python examples/eigen_two_storey_one_bay_frame.py

Each script builds the project, saves it, reloads it, and asserts a clean round-trip.