Which bar has the largest nominal diameter?

In reinforced concrete construction, the nominal diameter of reinforcing bars is indicated by their designated number, which corresponds to the bar's size in eighths of an inch. For instance, a #6 bar has a nominal diameter of 6/8 inches, a #8 bar has 8/8 inches (or 1 inch), a #9 bar has a nominal diameter of 9/8 inches (or 1.125 inches), and a #11 bar has 11/8 inches (or 1.375 inches).

Considering the nominal diameters, the #11 bar has the largest nominal diameter at 1.375 inches. Therefore, it is larger than each of the other bars listed. The #9 bar, which was selected, actually has a nominal diameter smaller than the #11 bar. As a result, the #11 bar is the correct answer, as it represents the largest diameter among the options presented. Understanding the sizing of reinforcing bars is crucial for ensuring structural integrity in concrete design and construction.