When designing a reinforced concrete (RC) beam for a medium-rise residential building in Japan

When designing a reinforced concrete (RC) beam for a medium-rise residential building in Japan

When designing a reinforced concrete (RC) beam for a medium-rise residential building in Japan, which of the following factors is most critical for determining the beam’s flexural capacity?

A. The compressive strength of concrete (fck)

B. The yield strength of longitudinal reinforcing steel (fy)

C. The cross-sectional dimensions (width × effective depth)

D. The amount of shear reinforcement

E. The cover thickness of concrete

Answer: C

Explanation: The flexural capacity of an RC beam is primarily determined by its cross-sectional dimensions (effective depth and width) and the area of longitudinal reinforcement. While concrete and steel strength are important, the cross-sectional size directly governs the moment-resisting capacity, which is a key in Japanese structural design.