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version (9.42 MB) by Dr. Erol Kalkan, P.E.
Fast MatLAB function for nonlinear-inelastic time-history analysis of a SDOF oscillator.


Updated 15 Jun 2017

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Fast MatLAB function for nonlinear-inelastic time-history analysis of a single-degree-of-freedom (SDOF) oscillator.
The code runs for a single or a series of input excitations for parametric study. MatLAB is used for pre-processing; nonlinear SDOF system is constructed and solved using OpenSEES ( in the background. The user can define any nonlinear material model available in OpenSEES. Material properties are defined in InSPecReg/material.tcl.

Syntax: nonlinearSDOFmultiAxial

Note: Input ground motions are currently set to PEER format in PEER ground motion database at

Two example ground motions are provided, results are in ASCII format in ".out" files as inch/s² for acc.out, inch for disp.out

References (PDFs are available in folder named "docs"):

Kalkan, E. and Graizer V. (2007). "Multi-Component Ground Motion Response Spectra for Coupled Horizontal, Vertical, Angular Accelerations and Tilt", ISET, Journal of Earthquake Technology, March.

Kalkan, E. and Graizer V. (2007). "Coupled Tilt and Translational Ground Motion Response Spectra", ASCE Journal of Structural Engineering, 133(5): 609-619, 2007.

Kalkan, E. and Kunnath, S.K. (2008). "Relevance of Absolute and Relative Energy Content in Seismic Evaluation of Structures", Advances in Structural Engineering, 11(1): 17-34.

Kalkan, E. and Kunnath S.K. (2007). "Effective Cyclic Energy as a Measure of Seismic Demand", Journal of Earthquake Engineering, 11(5): 725-751.

Graizer, V. and Kalkan, E. (2008). "Response of Pendulums to Complex Input Ground Motion", Soil Dynamics and Earthquake Engineering, 28(8): 621-631.

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Updated notes

Updated references

Updated definition

MATLAB Release Compatibility
Created with R2014a
Compatible with any release
Platform Compatibility
Windows macOS Linux