Degrees of Freedom and Support Reactions

 In general, the direction that a joint can move (translate) or rotate is called a degree of freedom (DOF). Therefore, a joint can have a maximum of six degrees of freedom: three translations and three rotations. If a degree of freedom is restrained by a support from translation or rotation, a force or moment is applied from the support on the structure (support reaction). One has to note that rotation is always about an axis. To know about which axis the rotation occurs, if one uses his/her hand to show the rotation, the thumb represents the direction of the rotational axis.

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