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Physical scope

Understand the modeling assumptions before treating a synthetic response as a representation of a real structure.

Supported dynamics

DynaResp solves linear time-invariant second-order systems:

[ M\ddot{u}(t) + C\dot{u}(t) + Ku(t) = f(t). ]

Initial displacement and velocity are zero. Matrices are constant within one simulation sample, although a dataset builder may generate different matrices between samples.

Units

DynaResp performs no unit conversion. Inputs must use one consistent unit system. SI is recommended:

  • length in meters;
  • mass in kilograms;
  • force in newtons;
  • time in seconds;
  • Young's modulus in pascals;
  • density in kilograms per cubic meter.

Beam model

The single beam model is uniform and simply supported. It is assembled from two-node bending elements with transverse displacement and rotation at each node. This assumes small deflection, linear elastic behavior, and negligible shear deformation and rotary inertia. Finite-element modes are mass-normalized and reduced to the requested n_modes.

Damage model

Beam damage is represented by fractional stiffness reductions applied to one or more selected elements. It is designed as a transparent synthetic parameter and does not model crack geometry, contact, breathing behavior, or nonlinear fracture mechanics.

Moving loads

MovingLoad, TwoWheelLoad, and RunnerLoad require a continuous position domain, currently provided by Beam. They prescribe forces independently of structural motion and do not model suspension dynamics, road roughness, wheel lift-off, or coupled vehicle-structure interaction.

RunnerLoad represents successive half-sine foot contacts whose average vertical impulse matches body weight. It is not a biomechanical gait model.

Measurement effects

Sensor effects operate after state simulation. Noise, bias, clipping, quantization, sensitivity, and dropout do not feed back into the structural system.

Not currently modeled

  • geometric or material nonlinearity;
  • time-varying matrices within a sample;
  • nonzero initial conditions;
  • coupled fluid, soil, vehicle, or human interaction;
  • shear-deformable or torsional beam behavior;
  • automatic unit conversion;
  • parameter inference or system identification.

These are deliberate boundaries, not hidden approximations.