When modelling a structure there are situations in which members do not extend directly between two joints but are instead offset from the joints. In other situations, the intersection between two members may be relatively large and can be considered as a rigid link. In all these instances, the geometry of the model can be specified to more accurately model the structure by using rigid connections between the joints and the members. In Multiframe, these rigid connections are applied using Member Offsets.

Member Offsets are rigid links between a joint and the end of a member. They are infinitely stiff and do not deform in bending, shear or axially. Loading on members with rigid offsets is applied to the flexible portion of the member only (see Member Length on the diagram below) and distances used to specify the position of loads are measured from the ends of the rigid offsets.

When Member Offsets are specified, Multiframe considers the length of the member to be the length of the flexible portion of the member. (Member Length in the diagram above)

To set the Member Offsets on a member

§    Select the member or members to be modified

§    Choose Member Offsets from the Frame menu

§    Click on the radio button corresponding to the axes from which the offset connections will be measured.

§    Type in the size of the offset connections at both ends of the members.

§    Click on the OK button

The size of the offset connections may be specified using global or local axes. If local axes are selected, the offset connections are measured relative to the local axes as defined by the joints at the end of the members. (see Local Axes between joints below) Note that this is distinctly different from the true local member axes which are aligned with the actual position and orientation of a member after the member offset has been applied.