What is the role of expansion joints in bridges?

• A. Seismic dampers
• B. Guard rails
• C. Expansion joints
• D. Bearing pads

Answer: (C)

Expansion joints are built to let bridge segments move apart and come back together as the structure expands and contracts with temperature changes, plus other horizontal movements from loads and wind. By providing a controlled gap that is designed to accommodate this movement, they prevent excessive stresses from building up in the deck and substructure, which could cause cracking, spalling, or buckling. They also host sealants or weatherproof components to keep water and debris out, helping the deck last longer.

This is the best fit because other features serve different roles: seismic dampers absorb energy during earthquakes, guard rails protect safety, and bearing pads support vertical loads and allow some limited movement at the supports but do not accommodate the long-range horizontal expansion between deck sections. Expansion joints specifically bridge that gap and control movement across the joint.