This is the ENGLTHA SDOF nonlinear dynamics software website.
The program performs Dynamic Time History Analysis for one of 2 possible cases: (1) A Nonlinear SDOF oscillator under
an earthquake ground acceleration record, and (2) A Nonlinear or Linear SDOF oscillator under any applied forcing function.
For case (1) the acceleration record is selected from a set of records supplied by the PEER Strong Motion Catalogue.
For case (2) the forcing function is in the form of a user-supplied text file of (time, acceleration) data points. In
either case, the program presents the response results as graphs of the relative displacement-time history, the acceleration-time
history, and the restoring force-displacement or hysteresis loops. The results are also stored as ASCII files for possible
The ENGLTHA program is intended for educational use.
It can be used to engage students in:
• Numerical simulation of the nonlinear or linear response of structures
• Comparison of simulated
vs actual structural response
• Parametric investigations of building response under earthquakes
of linear or nonlinear response spectra
• Comparison of the results with code-based calculations
of other structural dynamics programs
• Replication of textbook examples and problems
awareness of the role of research in engineering
A research version of ENGLTHA also exists for the development of simplified dynamic analysis methods.