The OpenSees Examples Primer
Version 1.2
August 20, 2001
Frank McKenna and Michael Scott
Pacific Earthquake Engineering Research Center University of California, BerkeleyIntroduction
To conduct a simulation, the user creates various objects which serve either of three main purposes:
Modeling: The user first creates a ModelBuilder object which defines the type of model, and commands available for building the model. With a ModelBuilder defined, the user then creates the Element, Node, LoadPattern and Constraint objects that define the model. In this primer, the use of a basic ModelBuilder will be demonstrated.
Analysis: After defined the model, the next step is to create the Analysis object for analyzing the model. This may be a simple static linear analysis or a transient non-linear analysis. In OpenSees, an Analysis object is composed of several component objects, which define how the analysis is performed. The component objects consist of the following: SolutionAlgorithm, Integrator, ConstraintHandler, DOF_Numberer, SystemOfEqn, Solver, and AnalysisModel. This approach provides a great deal of flexibility in how an analysis is conducted.
Post-processing: Once the model and analysis have been defined, the user has the option of specifying what is to be monitored during the analysis. This, for example, could be the displacement history at a node or internal state of an element in a transient analysis or the entire state of the model at each step in the solution procedure. Several Recorder objects are created to store what the user wants to examine.
In the examples, Tcl scripts are used to create a model, analysis, and output specification. The examples are (1) simple truss structure, (2) reinforced concrete portal frame, (3) two-story multi-bay reinforced concrete frame, and (4) a three-dimensional frame. The examples are not meant to be completely realistic, but they are representative of typical structures. The analyses performed on these models consist of simple static analysis, pushover analysis and transient analysis. An example of moment-curvature analysis is also performed on a reinforced concrete section.
…or other spreadsheet programs will find that many of the concepts are transferrable to pandas.
…or other spreadsheet programs will find that many of the concepts are transferrable to pandas.