2.12Fixities

Initially, all joints are assumed to be free. In other words, they are free to move along or rotate about the active axes. A fixed or restrained joint (support) is a joint that has one or more of its active degrees of freedom restrained.

For 2-D truss structures, joint displacements along the X and Y axes can be restrained. For 2-D frame structures, joint rotation about the Z axis, as well as its displacements along the X and Y axes can be restrained. For 3-D truss structures, joint displacements along the X, Y, and Z axes can be restrained. For 3-D frame structures, joint displacements along the X, Y, and Z axes, as well as its rotations about the axes can be restrained.