Why are integral end bents designed without expansion joints?

Integral end bents are designed without expansion joints primarily to facilitate thermal stress transfer. This design allows the end bent and the superstructure to act as a single unit, thereby enabling them to expand and contract in response to temperature changes without creating the potential for significant stress buildup at joints. By eliminating expansion joints, integral end bents minimize the risk of thermal-induced cracking and other issues that can arise from the movement of materials due to temperature fluctuations.

This approach simplifies the structural integrity of the bridge, allowing it to respond more uniformly to thermal changes. In contrast, joints can introduce weak points that are susceptible to problems such as water infiltration and corrosion, which can compromise the overall durability of the structure.

The other options, such as allowing for movement flexibility, reducing complexity in construction, and enhancing structural redundancy, do not capture the primary function of integral end bents in the context of thermal stress. While there may be some indirect benefits associated with those aspects, the major reason focuses on managing thermal movements effectively.