Local Axes in ETABS

Vertical Line Objects. For vertical line objects the local axes have the following default orientation:

• Local axis 1 is along the line object. The positive local 1 axis is in the same direction as the positive global Z-axis, upward.
• Local axis 2 is perpendicular to the line object. The projection of the positive local 2 axis onto the global X-axis is in the same direction as the positive global X-axis.
• Local axis 3 is perpendicular to the line object. The direction of the positive local 3 axis is determined from applying the right-hand rule using the directions of the 1 and 2 axes described in the preceding bullets.

Horizontal Line Objects. For horizontal line objects (parallel to the global X-Y plane), the local axes have the following default orientation:

• Local axis 1 is along the line object. The projection of the positive local 1 axis onto the global X-axis is in the same direction as the positive global X-axis. If the line object is parallel to the global Y-axis such that there is no projection onto the global X-axis, the positive direction of the local 1 axis is the same as the direction of the positive global Y-axis.
• Local axis 2 is perpendicular to the line object. The positive local 2 axis points in the same direction as the global Z-axis, upward.
• Local axis 3 is perpendicular to the line object and is horizontal. The direction of the positive local 3 axis is determined from applying the right-hand rule using the directions of the 1 and 2 axes described in the preceding bullets.

Other (neither vertical nor horizontal) Line Objects. For line objects that are not vertical and are not horizontal, the local axes have the following default orientation:

• Local axis 1 is along the line object. The positive local 1 axis has an upward sense. The projection of the positive local 1 axis onto the global Z-axis is in the same direction as the positive global Z-axis, upward.
• Local axis 2 is perpendicular to the line object. The local 1-2 plane is vertical. The positive local 2 axis has an upward sense. The projection of the positive local 2 axis onto the global Z-axis is in the same direction as the positive global Z-axis, upward.
• Local axis 3 is perpendicular to the line object and is horizontal. The direction of the positive local 3 axis is determined from applying the right-hand rule using the directions of the 1 and 2 axes described in the preceding bullets.