What is the maximum on center spacing for vertical reinforcement in a 12 inch nominal thickness reinforced concrete foundation wall?

The maximum on-center spacing for vertical reinforcement in a 12-inch nominal thickness reinforced concrete foundation wall adheres to the guidelines set forth in building codes and industry standards. For various structural applications, maintaining proper spacing of vertical reinforcement is crucial for ensuring the structural integrity and performance of the wall.

In this case, the correct answer of 72 inches aligns with the general standards for vertical reinforcement spacing in concrete walls. This specification ensures that enough reinforcement is present to manage the tensile forces within the concrete, particularly given the wall's thickness. Spacing the reinforcing bars too far apart could lead to a reduction in the wall's overall load-bearing capacity and increase the risk of cracking or structural failure under load.

The other options present spacings that exceed the generally accepted limits for structural integrity in reinforced concrete applications. Choosing a spacing greater than 72 inches could compromise the wall's strength and safety, which building codes aim to prevent. Therefore, the correct choice reflects the balance between adequate reinforcement and efficient construction practices.