What occurs when the structure's center of mass does not coincide with the center of rigidity?

When a structure's center of mass does not align with its center of rigidity, it leads to torsional shear stress. This misalignment causes the structure to experience a twisting effect when subjected to lateral forces, like wind or seismic activity.

The center of mass is the point at which the mass of the structure is balanced, while the center of rigidity is the point that reflects the distribution of lateral stiffness in the structure. When these two points do not coincide, any lateral load will induce a torque that results in rotation around the center of mass. This rotation creates torsional shear stresses in structural members, which can lead to structural failure if not adequately designed to resist such stresses.

This understanding of how torsional shear stress arises from the misalignment of the center of mass and the center of rigidity is crucial for engineers during the design phase, especially in areas prone to dynamic loading conditions.