Crack spacing-Figure 7 depicts the crack spacing of the beams. To facilitate a comparison among the beams, three categories were used: total average crack spacing along the loading span; spacing within the constant moment zone; and spacing outside the constant moment zone (that is, shear span). The average crack spacing within the constant moment zone of the control beam was 30.5 mm (1.2 in.), while the spacing outside the constant moment zone was 40.9 mm (1.6 in.). This illustrates that the concrete in the constant moment zone was subjected to a greater curvature than that outside the zone and, hence, more cracks tended to develop when a bending moment was applied. The beams strengthened with NSM CFRP showed noticeably larger crack spacing compared to the control. For example, the average total crack spacing of S0-1 and S0-2 was 205.3% and 177.0% greater than that of the control beam, respectively. This observation is explained by the fact that the flex ural stresses applied to the tensile region of the strengthened beams were redistributed along the NSM CFRP and the adhesive layer additionally dissipated these stresses, thereby precluding the formation of secondary cracks between the primary :flexural cracks (as shown in Fig. 6(a), the secondary crack length was typically less than 50% of the primary crack length) . The same observation is valid for conventional RC at a service load level: adding more steel reinforcement results in wide crack spacing.20 It is rather inconclusive to report that the crack spacing of the strengthened beams was controlled by the curvature of the constant moment zone, given there was no difference in crack spacin g within and outside the constant moment zone for the case of Beam S0- 1: the complex interaction betw een the epoxy-bonded NSM CFRP and the concrete could partially offset the curvature effect mentioned previously.