They Induce both vertical and horizontal forces during earthquake.

• A. Bridge Loads
• B. Live Load
• C. Water Current
• D. Seismic Loads

Answer: (D)

Earthquakes exert forces in both vertical and horizontal directions because ground motion accelerates the entire structure and the building’s mass resists that acceleration. The inertia forces that arise from this acceleration act in all directions, producing horizontal base shear and bending moments, as well as vertical forces that affect axial loads in columns and floors. This combination of forces is what engineers refer to as seismic loads. The other options describe loads not inherently tied to earthquake action: bridge loads are primarily gravity and live loads from traffic, live load is variable occupancy, and water current is a hydrodynamic force from flowing water. Seismic loads are specifically the loads generated by earthquake effects, including both vertical and horizontal components.