The Earthquake Engineering Online Archive

NONLIN: Nonlinear Dynamic Time History Analysis of Single Degree of Freedom Systems

Charney, Finley A.

Advanced Structural Concepts, Incorporated, under a contract with the Federal Emergency Management Agency,

NONLIN is a Microsoft Windows based application for the dynamic analysis of single degree of freedom structural systems. 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. See Clough and Penzien for a theoretical description of the solution technique. 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.

Available online: http://training.fema.gov/EMIWeb/nonlin.asp