What is the distance between the Center of Rigidity and the Center of Mass called?

The distance between the Center of Rigidity and the Center of Mass is referred to as eccentricity. This concept is particularly important in structural engineering and dynamics, as it describes the degree of separation between the point where mass is effectively concentrated (the Center of Mass) and the point where lateral forces are resisted (the Center of Rigidity).

Eccentricity plays a crucial role in understanding how structures respond to lateral loads, such as wind or seismic activity. When the Center of Mass and Center of Rigidity are not aligned, the resulting eccentricity can lead to torsional effects that may impact the stability and safety of a structure. Thus, understanding and calculating eccentricity is essential for engineers to ensure that structures behave predictably under various loads.

The other options do not pertain to this specific relationship in structural behavior. For example, "soft story" refers to a level in a building that has significantly weaker lateral strength, while "elasticity" is a material property relating to its ability to deform elastically under stress. "Relaxation" generally refers to the decrease in stress over time under constant strain. These terms do not directly relate to the concept of distance or spatial relationship between the Center of Rigidity and Center of Mass.