Basic Examples Manual

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The objective of this primer is to provide new users of OpenSees (Open System for Earthquake Engineering Simulation) familiar structural engineering examples as a convenient method for learning how to use the software.

To conduct a simulation in OpenSees, the user creates an input file (a script). A script is just a series of commands that instruct the interpreter what to do. In the case of OpenSees, the commands either create objects or invoke methods (procedures) on those objects. In OpenSees there are 3 types of objects the user must create:

  1. 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 the basic ModelBuilder will be demonstrated.
  2. Analysis: After the user has 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 and these define the type of analysis that is performed. The component objects consist of the following: SolutionAlgorithm, Integrator, ConstraintHandler, DOF Numberer, SystemOfEqn, Solver, and ConvergenceTest. This approach provides a great deal of flexibility in how an analysis is conducted, but requires knowledge on behalf of the user as to what the different options provide.
  3. Output Specification: Once the model and analysis have been defined, the user must specify what is to be monitored during the analysis. OpenSees by default will producde no output. The outputs specified could for example be the displacement history at a node or internal stress state at some material point in an element element. The user typically creates Recorder objects to store what the user wants to examine, though the user can also use the tcl puts command.

In each of the following examples, tcl scripts are used to create model, analysis and a recorder objects. After these objects have been created, the analysis is performed. The analyses performed on these models consist of simple static gravity analysis and pushover analysis and transient analysis of models subjected to earthquake excitation. The examples are not meant to be completely realistic, but they are representative of typical structures. They are intended to remain s

  1. Truss Example
  2. Moment Curvature Example
  3. Reinforced Concrete Portal Frame Example
    1. Reinforced Concrete Portal Gravity Analysis
    2. Reinforced Concrete Portal Pushover Analysis
    3. Reinforced Concrete Portal Earthquake Analysis
  4. Elastic Frame Example
  5. Steel Frame Example
  6. Simply supported beam modeled with two dimensional solid elements
  7. Time History Analysis of a 2D Elastic Cantilever Column
  8. Eigen analysis of a two-story shear frame
  9. Eigen analysis of a two-storey one-bay frame