Which is a step in analyzing a bridge structure?

Determining horizontal and vertical forces is a crucial step in analyzing a bridge structure because it helps engineers understand the various loads the bridge must support during its use. This includes the weight of the bridge itself (dead load) and the additional weight from vehicles, pedestrians, and environmental factors like wind or snow (live load).

By calculating the horizontal forces, such as those caused by wind pressure or seismic activity, and vertical forces related to the load applied on the bridge, engineers can assess how these forces interact and affect the overall stability and performance of the bridge. Understanding these forces allows for proper design modifications to ensure safety and functionality over the bridge's lifespan.

While the other options involve important considerations in bridge analysis, they do not encompass the fundamental forces that impact the structure’s integrity. Calculating material elasticity, measuring total weight, and visual inspections are all valuable, but they are secondary to the primary analysis of forces that dictate the bridge's performance under load.