Frame Element Internal Forces

The frame element internal forces are:

These internal forces and moments are present at every cross section along the length of the frame element.

For each load case and load combination, the frame element internal forces and moments are computed and reported at each frame element output station.

In frame element output displayed in a tabular form, either on the computer screen, printed to a printer or printed to a file, the locations of the output stations are identified by the absolute distance to the station measured from the i-end of the element.

Frame Element Sign Convention

The sign convention for frame element internal forces is illustrated in the figure below. This sign convention can be described by defining the concept of positive and negative faces of an element. Consider a section cut through the element in the 2-3 plane. At this section, the positive 1 face is the face whose outward normal (arrow that is perpendicular to the section and pointing away from the section) is in the positive local 1 direction. At this same section, the negative one face is one whose outward normal is in the negative local 1 direction. The positive 2 and 3 faces are those faces with outward normals in the positive local 2 and 3 directions, respectively, from the neutral axis. Note the following about the frame element internal forces: