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58 (a) Class 1 Exposure; d = 1.00 (b) Class 2 Exposure; d = 0.75 Figure 38. Measured versus calculated crack widths. conservative nature of existing AASHTO crack control require- and is based on fundamental mechanics, rather than being ments (Equation 5) is evident in Figure 38, supporting the dis- empirically calibrated as is Branson's Equation. Bischoffs cussion in Section 1.3.7.2. approach is also appropriate for any type of elastic reinforc- ing material. The average measured crack widths are below the present 2.9.3 Summary and Conclusions AASHTO de facto limits for Class 1 and Class 2 exposure. The The AASHTO LRFD specifications use the Branson for- inherent conservativeness in existing equations allows pres- mulation for computing an effective moment of inertia used ent specifications to be extended to the anticipated higher to compute deflection. An alternative approach developed service level stresses associated with the use of high-strength by Bischoff has been demonstrated to yield similar results reinforcing steel.