Global and Local axes for beams

The model is created related to a global axes system XYZ that is unique for the entire problem. But every beam must have its own local axes system X’Y’Z’ in order to:

  1. Refer section properties like Inertia modulus or thickness and height to this system.
  1. Some of the loads (that have the prefix Local ) are related also to this system.
  1. Strength results over the beams are referred to this local axes system.

The main property of this system is that the local X’ axe must have the same direction than the beam.

The ways for defining local axes systems are:

  1. Default . The program assigns a different local axes system to every beam with the following criteria:

Note: The intuitive idea is that vertical beams have the Y’ axe in the direction of global X. All the other beams have the Y’ axe horizontal and with the Z’ axe pointing up.

  1. Automatic . Similar to the previous one but the local axes system is assigned automatically to the beam by GiD. The final orientation can be checked with the Draw Local Axes option in the GiD Conditions window.
  1. Automatic alt . Similar to the previous one but an alternative proposal of local axes is given. Typically, User should assign Automatic local axes and check them, after assigning, with the Draw local axes option. If a different local axes system is desired, normally rotated 90 degrees from the first one, then it is only necessary to assign again the same condition to the entities with the Automatic alt option selected.
  1. User defined . User can created different named local axes systems with the GiD command:

Data->Local axes->Define

and with the different methods that can be chosen there. The names of the defined local axes will be added to the menu where Local axes are chosen.

Note 1 : rambshell tries to correct the local axes system if the local X’ axe does not point to the direction of the beam. It will fail if local X’ axe is orthogonal to the direction of the beam.

Note 2 : The final local axes system for every beam can be visualized in the postprocess stage. It is convenient to check the correctness of these systems after calculation is performed.