Britannica
Sources used in this answer
What forces act on the top and bottom of a bending beam bridge?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
bridge
The multiple-span Seto Great Bridge over the Inland Sea, linking Kojima, Honshu, with Sakaide, Shikoku, Japan.
In the context of bridge engineering, a beam bridge carries vertical loads through the process of bending. As the beam bends, it experiences two primary horizontal forces acting on its cross-section:
- Top: The top of the beam undergoes horizontal compression, where the material is being pushed together.12
- Bottom: The bottom of the beam is subjected to horizontal tension, where the material is being pulled apart.12
These internal forces are fundamental to the structural integrity of the bridge. For example, in prestressed concrete construction, engineers utilize these properties by designing the concrete to resist the compressive forces at the top, while embedding steel to withstand the tensile forces at the bottom. Similarly, in a truss bridge, which functions like a simply supported beam, the top chords experience compression while the bottom chords experience tension.23