Outline typical retrofitting techniques to improve seismic resilience, such as FRP wrapping, external bracing, and base isolation.

• A. FRP wraps increase strength and ductility; external bracing adds lateral stiffness; base isolation decouples ground motion; all enhance seismic resilience.
• B. Painting the bridge, doing drainage, and sandblasting.
• C. Replacing steel with timber.
• D. Adding more lanes without structural changes.

Answer: (A)

Strengthening a bridge for earthquakes focuses on making the structure stronger, more ductile, and better at absorbing energy while limiting how much it moves during shaking. FRP wrapping around columns or joints improves confinement of concrete, raising strength and ductility and delaying buckling under shear; it’s lightweight, versatile, and can retrofit existing members without adding significant dead load. External bracing adds lateral stiffness and redundancy, helping to limit interstory drifts and redistribute seismic forces so the structure shares the load more effectively during an earthquake. Base isolation places bearings or isolators at the foundation to decouple the superstructure from ground motion, dramatically reducing transmitted accelerations and damages by allowing the building to move somewhat independently of the ground. Together, these approaches address different aspects of seismic demand and are commonly used in retrofit projects to improve resilience. Other activities like painting, drainage work, or sandblasting are maintenance or non-structural upgrades and don’t substantially improve seismic performance, and simply adding lanes without changing the structural system doesn’t enhance how the bridge would respond to earthquakes.