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Nonlinear finite element analysis.

xara is a Python package that provides an intuitive and performant API for nonlinear finite element analysis, implemented in C++ through the OpenSeesRT framework. OpenSees features state-of-the-art finite element formulations and solution algorithms, including mixed formulations for beams and solids, over 200 material models, and an extensive collection of continuation algorithms to solve highly nonlinear problems.

This package may be used as a drop-in replacement for both OpenSees.exe and OpenSeesPy (see Getting Started below), and generally provides a substantial performance boost.

Getting Started

The xara package can be installed into a Python environment in the standard manner. For example, using pip:

pip install xara

There are several ways to use the xara package:

• The standard way to use xara from Python is to create a xara.Model, and invoke its methods:

  model = xara.Model(ndm=2, ndf=2) # Create a 2D model with 2 DOFs per node
  model.node(1, 2.0, 3.0)
  ...

  Most of the functions from the OpenSeesPy library can be invoked directly as methods of a xara.Model without any changes in syntax, although it is generally encouraged to use the safer variants supported by xara. For example:

  # BAD
  model.pattern("Plain", 1, "Linear")
  model.load(1, 2.0, 3.0)
  # GOOD
  model.pattern("Plain", 1, "Linear")
  model.load(1, 2.0, 3.0, pattern=1)

• To start an interactive Tcl interpreter run the shell command:

  python -m opensees

  To quit the interpreter, just run exit:

  opensees > exit

• To execute Tcl procedures programmatically from Python, create an instance of the xara.Model class and call its eval() method to evaluate Tcl code:

  model = xara.Model()
  model.eval("model Basic -ndm 2")
  model.eval("print -json")

• The xara package exposes a compatibility layer that exactly reproduces the OpenSeesPy functions, but does so without mandating a single global program state. To run OpenSeesPy scripts, just change the import:

  import openseespy.opensees

  to

  import opensees.openseespy

  For true stateless modeling, the Model class should be used instead of the legacy model function; see the documentation here.

Development

To compile the project see about/compiling

Support