How do temperature changes affect deck expansion joints and overall bridge performance?

• A. Expansion joints must be oversized to absorb movement, causing no leakage.
• B. Joints must be fixed in place so deck cannot move.
• C. Temperature changes cause expansion and contraction; joints must accommodate movement without leakage or debonding, and deck performance must tolerate thermal stresses.
• D. Temperature changes do not affect deck joints.

Answer: (C)

Temperature changes cause the bridge deck and its supports to expand and contract. To keep the structure safe and durable, expansion joints must accommodate that movement within a designed range while preventing water ingress and seal debonding. This means joints are designed with proper gaps, seals, and movement mechanisms so the deck can slide and rotate slightly without tearing seals or compromising the deck surface. At the same time, the overall deck system and bearing details must tolerate the resulting thermal stresses and gradients, avoiding cracking, undue twisting, or bearing damage as temperatures vary. In essence, movement from temperature fluctuations is expected and planned for, and the joint design plus deck detailing must allow that movement without leakage or loss of performance.