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Rotated response spectrum calculation implemented in Python.

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Acceleration response spectrum calculations implemented in Python.


Simple Python functions for calculating psuedo-spectral acceleration and rotated psuedo-spectral acceleration. The response of the single-degree-of-freedom oscillator is computed in the frequency domain along with frequency-domain interpolation to accurately capture the high-frequency characteristics.

The calculation of the response spectrum is performed using frequency domain transfer functions, as well as frequency domain interpolation methods to insure that the time step of the motions is greater than 10 times the natural frequency of the oscillator frequency. Two perpendicular ground motions can be rotated to compute the response at various percentiles. For example, the minimum, median, and maximum could be computed using percentiles of 0, 50, and 100. The orientation of both the minimum and maximum percentile are provided, but not orientation is provided for other percentiles because the rotate spectral acceleration is not monotonically increasing.


pyrotd is available from the Python Cheese Shop:

pip install pyrotd


Spectral accelerations may be computed for a single time series:

osc_damping = 0.05
osc_freqs = np.logspace(-1, 2, 91)
spec_accels = pyrotd.calc_spec_accels(
    time_step, accels, osc_freqs, osc_damping)

Rotated spectral accelerations may be computed for a pair of time series:

rot_osc_resps = pyrotd.calc_rotated_spec_accels(
    time_step, accels_a, accels_b, osc_freqs, osc_damping)

A more detailed example is in this Jupyter Notebook.


Please cite this software using the DOI.


0.6.1 (2023-06-30)

  • Tests np.version to accommodate change in keywords of np.percentile

0.6.0 (2023-06-19)

  • Added optimization based on Stewart et al. (2017) algorithm

  • Added support for computing rotated PGA, PGV, and PGD

0.5.4 (2018-07-27)

  • Added

0.5.3 (2018-07-27)

  • Fix packaging issues

0.5.2 (2018-03-26)

  • Bump version for PyPi conflict

0.5.1 (2018-03-23)

  • Added tests/ directory

  • Added support for computing: SA, PSV, SV, and SD.

0.5.0 (2017-06-15)

  • Added support for Python 2.7

  • Added support for multiprocessing

  • Changed from using setup.cfg for metadata.

0.4.6 (2017-04-19)

  • Changed to use setup.cfg

  • Incremented version several times due to issues releasing.

0.4.1 (2017-04-11)

  • Fix release via Travis.

0.4.0 (2017-04-06)

  • Changed to return numpy.recarrays

0.3.0 (2017-04-05)

  • Added example

  • Added support for typing

0.2.0 (2017-02-20)

  • Changed from camelCase to underscores

  • Added PEER NGA West2 test cases

  • Fixed: numpy.array creation

0.1.0 (2016-03-04)

  • First release on PyPI.

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