Frame

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Frame#

Frame elements are used to model slender structural members like beams and columns. All frame elements are constructed with the form

Model.element(name, tag, nodes, section, transform)

Add a frame element to the model.

Available frame elements include

Name

Description

PrismFrame

Prismatic linear-elastic frame

ForceFrame

Force formulation

CubicFrame

cubic displacment formulation

ExactFrame

geometrically exact displacement formulation

To use frame elements in OpenSees models, you’ll need to:

  1. Define nodes with appropriate coordinates

  2. Create a coordinate transformation with the element orientation

  3. Define section behavior for the element

  4. Create the frame element, connecting it to nodes, sections, and transformation

  5. Apply loads and boundary conditions

Loads include

Theory#

A frame element represents a directed medium with a scalar characteristic coordinate \(\xi\). The embedding in space is described by:

  • A vector field \(\boldsymbol{x}(\xi)\) identifying positions in space,

  • A rotation field \(\boldsymbol{\Lambda}(\xi)\), and

  • A vector field \(\boldsymbol{\alpha}(\xi)\) identifying cross-sectional warping.

Some phenomena that can be modeled with frame elements include:

  • Distrubuted loads

  • Follower loads

  • Plastic hinges

  • Arbitrarily large rotations

  • Lateral-torsional buckling of beams,

  • Restrained torsional warping

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