How do building codes reduce earthquake damage and what is base isolation?

• A. Codes set design standards for strength, ductility, and redundancy; base isolation uses flexible bearings to decouple the building from ground motion, reducing transmitted forces.
• B. Codes only address aesthetics; base isolation increases transmitted forces.
• C. Codes discourage retrofitting; base isolation makes buildings heavier.
• D. Base isolation is a zoning rule unrelated to engineering.

Answer: (A)

Building codes reduce earthquake damage by ensuring structures are designed with enough strength, ductility, and redundancy to resist shaking and stay intact enough to protect occupants. Strength means members can bear the expected loads; ductility means the building can deform without sudden failure; redundancy provides alternate load paths so a single broken element won’t cause collapse. Together, these rules guide materials, connections, and detailing so buildings perform safely during earthquakes.

Base isolation is a technique that places flexible bearings between the building and its foundation, allowing the structure to move somewhat independently from the ground. This decoupling reduces the forces and accelerations transmitted to the building during shaking and can shift the building’s natural response away from the earthquake’s strongest frequencies. The result is much lower forces on the structure, helping to preserve the superstructure while dampening damage.

The other options don’t fit because building codes are not about aesthetics, and base isolation does not increase transmitted forces or rely on zoning rules—it’s an engineering approach to lessen, not amplify, the effects of ground motion.