Nonlinear multi-axial constant ductility spectra (H,V,tilt)

Robust function to generate multi-component constant-ductility nonlinear-inelastic response spectra.

Robust function to generate multi-component constant-ductility nonlinear-inelastic response spectra for multi-axial simultaneous excitation including horizontal, vertical and rotational motions (i.e. rotational acceleration and tilt).
It also computes components of seismic input energy imparted to the SDOF oscillator.
Its features are:
- Multi-axial excitation (simultaneous horizontal, vertical and rotational input ground motions)
- Material nonlinearity is presented by Ozdemir's rate-independent force-displacement model
- P-delta (at global level) is included
- Spectral analysis for constant yield displacement
- Input energy computations and output results for components of absolute and relative energy
zip file contains reference papers and example input ground motions from Pacoima Dam and output results.