Which element is crucial to transferring weight in an arch, located at the apex?

Which element is crucial to transferring weight in an arch, located at the apex?

• A. Voussoir
• B. Keystone
• C. Spandrel
• D. Abutment

Answer: (B)

Weight transfer in arches relies on compression through the wedge-shaped blocks toward the supports, with the piece at the apex acting as the locking mechanism. The central keystone sits at the top of the arch and wedges the surrounding voussoirs into place, creating a continuous curve that directs the load downward and outward to the abutments. This locking action prevents the arch from spreading and failing under weight. The individual wedge pieces are called voussoirs, and the spaces around the arch relate to spandrels and abutments, which resist outward thrust, but the critical element at the apex that makes the arch stable is the keystone.

Weight transfer in arches relies on compression through the wedge-shaped blocks toward the supports, with the piece at the apex acting as the locking mechanism. The central keystone sits at the top of the arch and wedges the surrounding voussoirs into place, creating a continuous curve that directs the load downward and outward to the abutments. This locking action prevents the arch from spreading and failing under weight. The individual wedge pieces are called voussoirs, and the spaces around the arch relate to spandrels and abutments, which resist outward thrust, but the critical element at the apex that makes the arch stable is the keystone.