Local Coordinate Systems - General |
  
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Local Coordinate Systems - General |
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Each member or finite element has a local coordinate system. It is a Cartesian system that has a default orientation (when local angle equals 0) and may be changed at any time. The three axes are denoted by small letters x, y, z. They follow the right-hand rule.
The local coordinate system exists to facilitate input and output for member and finite elements. For example, point or line loads on a member may be most conveniently specified in the local coordinate system of the member. The element results such as shears and moments are output in the local coordinate system for design purposes.
Since the local coordinate systems directly affect input and results, it is always prudent to check them for correctness using the commands such as View > Annotate or Render. You may change the local coordinate systems using the commands such as Edit > Element Local Angle or Reverse Node Order for Selected Elements. It is the directional vectors that matter...the origin of the local coordinate system is insignificant in this program.
The local coordinate system is used in the following input:
-point, line, and surface loads on members and finite elements [may also be specified in the global coordinate system]
-member moment releases
The local coordinate system is used in the following output:
-member forces, moments, and local deflections
-shell forces, moments, and stresses
In the following sections, Vx, Vy and Vz (with lowercase subscripts) represent the local x, y, and z vectors respectively. VX, VY and VZ (with uppercase subscripts) represent the global X, Y, and Z vectors respectively. For vector algebra, please refer to relevant math textbooks.
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