The vertical members that support the upper structure are known as what?

The vertical members that support the upper structure are referred to as bents. Bents are structural frames that consist of vertical columns and usually horizontal beams, effectively serving as the supporting framework for an overhead structure, such as a bridge or a building. They play a critical role in distributing loads and providing stability to the upper structure.

In contrast, piers are typically vertical structures that support beams or girders but are often not as comprehensive as bents in terms of the frame's design. Piles are long, slender columns driven deep into the ground to provide foundational support, primarily in situations where the soil conditions are not suitable for standard foundations. Abutments, on the other hand, are the structures at the ends of a bridge that support the bridge's superstructure and retain the earth at the approaches. Understanding these definitions helps in recognizing the role of bents in supporting upper structures efficiently and how they interact with other structural elements.