Overview

Overview#

𝜒ara (pronouced Kar-ah, like the Gaelic word for “friend”) is a free and open source tool for simulating the nonlinear response of structural and geotechnical systems. 𝜒ara is developed by PEER as an alternative front-end to the simulation framework proposed by McKenna (1997). The design of the interface was guided by the demands of the BRACE2 project, for which a suitably reliable and performant solution was not available.

With 𝜒ara, nearly everything is done through an instance of the Model class. Rather than invoking functions directly from the xara module, one instead typically creates an instance of a model,

import xara
model = xara.Model(ndm=2, ndf=2)

then constructs and analyzes a finite element simulation by invoking its methods:

model.node(1, (0.0, 0.0))
model.node(2, (1.0, 0.0))
model.material("Elastic", 1, 29e3, 0.3)
model.element("Truss", 1, (1, 2), 1, 20.0)
model.analysis("Static")
model.analyze(1)

Documentation of these methods is organized as follows:

  • Modeling methods are used to add components to the finite element model.

  • Analysis methods are used to move the state of the model from one converged state to another via a number of trial steps.

  • Output methods allow one to obtain output from a finite element analysis, e.g. to record the node displacement history.