When modelling structures it is sometimes convenient to define restraints that are not aligned with the global coordinate system. In Multiframe, these types of restraints may be modelled by specifying the orientation of the local degrees of freedom at each joint. By default, these degrees of freedom are aligned with the global axes but this is not always necessary. The Joint Orientation dialog is used to specify an arbitrary local coordinate system at each joint. This local coordinate system defines the direction of the local degree of freedoms that are used for applying boundary conditions and loading to the structure.

The orientation of a joint is specified by 3 angles that measure the rotation of the local coordinate system from the global coordinate system. The right hand rule is used to determine the direction of the rotations.

To set the orientation of a joint;

§    Select the joint

§    Choose "Joint Orientation…" from Frame menu.

§    Enter the angles defining the orientation of the joint

§    Press OK

The orientation of a joint is displayed in the Frame and Load Windows. If the orientation of a joint is not aligned with the global coordinates then the axes of the local coordinates are displayed at the joint. The display of the local joint axes may be disabled via the Symbols dialog.

The joint displacements and joint reactions displayed in the Results Window are displayed in local joint coordinates. Global results for each of the displacement of reaction components are displayed in the tool tips in these tables.

Caution:

Multiframe files for structures using local joint loads are not compatible with versions of Multiframe prior to v7.5. These files may be read into the older version of Multiframe but analysis of these structures may cause the program to crash unexpectedly.