Which statement about vertical reinforcement and grout in seismic masonry design is true?

• A. They are not used in light-duty seismic walls.
• B. They provide compressive strength only.
• C. They increase wall stiffness only.
• D. They provide shear and flexural resistance, distribute forces, and improve ductility.

Answer: (D)

Vertical reinforcement with grout makes a masonry wall behave more like a ductile, continuous beam under seismic loads. The steel in vertical joints carries tensile forces that masonry alone cannot resist, adding shear resistance and flexural capacity. Grouting the cores bonds the masonry units to the reinforcement and to any adjacent leaves, creating a continuous member that distributes lateral forces rather than letting them concentrate at individual joints. This combination also improves ductility, allowing controlled deformation and energy dissipation during an earthquake, which reduces the likelihood of brittle failure. In short, these elements provide shear and flexural resistance, distribute forces across the wall, and enhance ductility.