In post-tensioned segmental bridges, what is the purpose of post-tensioning tendons after the concrete gains strength?

• A. To pre-stress the reinforcement before casting.
• B. To increase early strength of concrete.
• C. To lock segments together and develop compressive force to control cracking and reduce unstrained movement.
• D. To allow the deck to flex freely.

Answer: (C)

Post-tensioning tendons are used after the concrete gains strength to press the segments together and put the deck into compression. This creates a continuous compressive force along the prestressed conduit path, which counters the tensile stresses that arise under service loads. By locking the segments, it controls cracking at joints and minimizes unrestrained movement between segments, helping to maintain alignment and stiffness of the bridge.

This approach doesn’t primarily aim to increase early strength of the concrete, nor does it involve pre-stressing reinforcement before casting, and it isn’t intended to let the deck flex freely. Instead, the applied prestress produces a beneficial compressive state that improves crack control, durability, and overall load-transfer performance of the post-tensioned segmental bridge.