The model has been 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.
2. Some of the loads (that have the prefix Local) are related also to this system.
3. Strength results over the beam 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.
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The ways for defining local axes systems are:
· X' axe has the direction of the beam.
· If X' axe has the same direction than global Z axe, Y' axe has the same direction than global X. If not, Y' axe is calculated so as to be horizontal (orthogonal to X' and Z).
· Z' axe is the cross product of X' axe and Y' axe. It will try to point to the same sense than global Z (dot product of Z and Z' axes will be positive or zero).
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.
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.
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