How do curved steel tendons strengthen a prestressed-concrete bridge beam?

In prestressed concrete bridge beams, curved steel tendons are used to enhance structural performance through two primary mechanisms:

• Compression: Once the tendons are stretched and anchored at the ends of the beam, they exert a high-tension force that pulls the anchored ends together. This action places the entire concrete beam into a state of horizontal compression, which helps the material resist the tensile forces that naturally occur when a beam bends under a load.1
• Upward Force: Because the tendons are curved upward from end to end, they exert an upward force on the beam. Designers strategically utilize this force to counteract a significant portion of the downward load the bridge is expected to carry.1

By combining these effects, prestressed concrete allows for more efficient, lighter, and often less expensive designs compared to traditional reinforced concrete, as it minimizes the amount of material required while maximizing the beam's load-bearing capacity.1