16/03/2023
Understanding FEA Software Coordinate System is CRUCIAL in interpreting the structural analysis results.
Neglecting the understanding of the coordinate system used by Finite Element Analysis (FEA) software (e.g. STAAD,ETABS,SAP) can lead to erroneous interpretation of the calculation output. It is crucial to understand the difference between local and global coordinate systems and how they are used in the software to correctly interpret the results.
In FEA, the global coordinate system is the reference system used to define the overall position and orientation of the structure being analyzed. The local coordinate system, on the other hand, is used to define the position and orientation of individual components or parts within the structure. These local coordinate systems can be different for different components of the structure.
When performing structural analysis using FEA software, we are converting the physical geometry of the structure into a digital model consisting of elements and nodes. The software uses the global coordinate system to locate the nodes and elements in space and to define the overall position and orientation of the structure. However, for each element, the software also defines a local coordinate system, which is used to determine the position and orientation of the element in relation to the overall structure.
The interpretation of the structural analysis results depends on a thorough understanding of the coordinate system used by the FEA software. A misinterpretation of the results can occur when the user assumes that the software is using a different coordinate system than what is actually being used. For example in STAAD, the reaction forces(i.e. Fx,Fy,Fz,Mx,My,Mz) are reported using the global coordinate system and the member forces are reported using the elements local coordinate system. If the user assumes that the software is using a local coordinate system when it is actually using a global coordinate system, then the interpretation may be incorrect and can lead to wrong design assumptions which may result to a catastrophic design.
A correct interpretation of the results obtained from FEA software requires a thorough understanding of the coordinate system used by the software. Neglecting this understanding can lead to erroneous interpretations of the calculation output. The difference between local and global coordinate systems should be understood to correctly interpret the results.