Understanding 3D Frame Element in Structural Analysis

A paper presents how to apply rotation matrix and direction cosine to 3d frame analysis

In structural analysis of 3D frame structures, the element coordinates, so-called local coordinates, must be transformed (rotated) to the global coordinate system. The reason behind this is to bring the element with different alignment to the same coordinate system for force (and stiffness) assembly at nodes. Understanding the concept behind this transformation is crucial for studying how the matrix structural analysis works.