In real-life, structures are all three-dimensional objects. In analysis, however, depending on the layout of elements, we can analyze our model in a plane or in space. The methods and procedures we will use to analyze structures will also depend on whether it is 2D or 3D.
Planar (2D)
When loads and certain parts of a structure all coincide in one plane, it is a planar structure (2D). We can analyze its reactions, internal forces/stresses, and deflections in said plane. Examples would be beams, plane trusses, and plane frames.
Spatial (3D)
There are instances when the loads and arrangement of members of a structure cover all three dimensions, such as transmission towers or grid trusses. These examples are said to be spatial structures. In these cases, we need to analyze it in all three dimensions.
Summary
In real-life, structures are all three-dimensional objects; however, we can analyze structures either in 2D or in 3D.
When loads and structures coincide in one plane, it is a plane structure (2D); On the other hand, when it covers all three dimensions, it is a spatial structure (3D)
The methods and procedures we will use to analyze structures will also depend on whether it is 2D or 3D.
