Where does the applied seismic force act on a structure?

The applied seismic force acts on the Center of Mass of a structure. This is because the Center of Mass represents the average position of all the mass in the structure, and it is the point at which gravitational forces effectively act. During seismic events, the inertia of the mass and the ground motion influence how forces are distributed through the structure. The Center of Mass helps to simplify the analysis of the dynamic response of the structure, as it is this point that will experience the most significant effects of acceleration due to seismic forces.

In structural engineering, recognizing that the seismic forces are applied at the Center of Mass allows for accurate modeling of how the building will react during an earthquake. This understanding is crucial for designing structures that can withstand seismic activity, thus ensuring safety and structural integrity.

Considering the other options, the Center of Gravity is often related to gravitational forces, which may not accurately represent the dynamic forces experienced during seismic activity. The Base of the Structure typically relates to where loads are transferred to the foundation rather than the point of force application. The Point of Support refers to specific locations where structures are supported but does not capture the distributed nature of seismic forces across a structure. Therefore, focusing on the Center of Mass provides the best understanding of how these forces should be analyzed