Axis sets are used as reference in modeling and analyzing stages of a building system. There are two axes sets to be used as reference in the SAP2000 program: global axes set and local axes.
For the purpose of structural analysis and design, a building model is created that is as much as possible. The first step in creating this model is to define axles. At this stage, the axles are created according to the global axis team. As seen in Figure-1, the global axis team in SAP2000 was created according to the right-hand rule.
LOCAL AXES IN SAP2000
In the SAP2000 program, besides the global axis (X-Y-Z) common to the entire system, there are local axis sets (1-2-3) specific to each element in the model. Loads acting on the structure can be entered into the program according to the user’s choice according to both axis sets. However, when the structure is analyzed under loads, it is of great importance for engineering to interpret the analysis results correctly. The program presents the results of the structural analysis to the user, taking into account the local axis set. In this context, anyone who uses the program should be able to master what local axes are.
As an example, let’s consider a 3-dimensional structure model consisting of carrier system frames. There are 6 degrees of freedom at each node of this building system, 3 of which are translational (U) and 3 of which are rotation (R). Degrees of freedom at the node can be schematized as shown in Image-2. An example of the symbols in the figure can be explained as follows: ” U1; 1 is the translation in the direction of the local axis, R1; 1 denotes the rotation around its local axis. ”
In the SAP2000 program, local axes 1,2 and 3 are represented by colored arrows. The colors corresponding to the local axes are as follows:
1 ➞ RED
2 ➞ GREEN
3 ➞ BLUE
The local axes of all the elements (column, beam, floor, foundation, etc.) in the modeled structure can be displayed on the screen by following the steps below.
➞ View menu
↳ Set display options
↳ Lokal axes ✓ (joints, frame elements, etc. for)
Figure-3 of an exemplary structure where the local axes of columns, beams and floors are seen can be seen in Figure-3: