STAAD.Pro allows specifications of supports that are parallel as well as inclined to the global axes.
Supports are specified as PINNED, FIXED, or FIXED with different releases. A pinned support has restraints against all translational movement and none against rotational movement. In other words, a pinned support will have reactions for all forces but will resist no moments. A fixed support has restraints against all directions of movement.
The restraints of a fixed support can also be released in any desired direction as specified. See TR.27.1 Global Support Specification for details.
Translational and rotational springs can also be specified. The springs are represented in terms of their spring constants. A translational spring constant is defined as the force to displace a support joint one length unit in the specified global direction. Similarly, a rotational spring constant is defined as the force to rotate the support joint one degree around the specified global direction. See TR.27.4 Multilinear Spring Support Specification for details.
For static analysis, Multi-linear spring supports can be used to model the varying, non-linear resistance of a support (e.g., soil). See TR.27.3 Automatic Spring Support Generator for Foundations for descriptions of the elastic footing and elastic foundation mat facilities.
The Support command is also used to specify joints and directions where support displacements will be enforced.