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NONLIN: Nonlinear Dynamic Time History Analysis

A computer program for nonlinear dynamic time history analysis of single- and multi-degree-of-freedom systems.

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Version 1.0 - published on 06 Oct 2011

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NONLIN is a Microsoft Windows based application for the dynamic analysis of primarily single degree of freedom structural systems.  Version 8.00 of NONLIN has also capabilities that allow you to model more complicated structures, with more complex hysteretic properties.  The basic model has three degrees of freedom per story, with the capability to analyze base isolated structures and structures incorporating passive energy devices up to three stories in height. The structure may be modeled as elastic, elastic-plastic, or as a yielding system with an arbitrary level of secondary stiffness.  The secondary stiffness may be positive, to represent a strain hardening system, or negative, to model P-Delta effects.  The dynamic loading may be input as an earthquake accelerogram acting at the base of the structure, or as a linear combination of sine, square, or triangular waves applied at the roof of the structure.  The program uses a step-by-step method to solve the incrementally nonlinear equations of motion.


Below is a screen shot of NONLIN input window.



While NONLIN may be used for professional practice or academic research, the fundamental purpose of the program is to provide a visual basis for learning the principles of earthquake engineering, particularly as related to the concepts of structural dynamics, damping, ductility, and energy dissipation. All input for NONLIN is carried out interactively through the use of the computer keyboard and the mouse.  For the current version, plots are written to the screen in several different “windows” and tabular output information can be written to output files that can be saved to disk. These files include a text file with the .OUT extension which summarizes the latest run and tab-delimited files with .XL1 file extension.  These tabular data files are intended for use with a spreadsheet program such as Microsoft Excel. This allows you to perform further processing of the data or to graph the output data for inclusion in reports and other documents.  The .XL1 files can be viewed or printed from a simple text processing program such as Microsoft WordPad.  Graphical screen plots of several different types are produced during program execution.  Hard copies of any of the screen plot windows may be obtained. Please refer to the manual posted under attachments.


After the structural properties and loading have been input, you may obtain the following information:






For further information, please refer to the manual posted under attachments.




Developed by Finley A. Charney

Virginia Polytechnic Institute and State University

Department of Civil and Environment Engineering

200 Patton Hall

Virginia Tech, Blacksburg, VA 24061  USA


Cite this work

Researchers should cite this work as follows:

  • (2011), "NONLIN: Nonlinear Dynamic Time History Analysis,"

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