## 3 Results and Discussion
### Experimental Service Load  
Often the required amount of reinforcement in a section is a consequence of fulfilling the serviceability criteria, which consider the limitations of maximal crack widths, deflection, and stresses in the FRP reinforcement. In ACI-15 [29], the beam deflection is limited to L/360 in the case where the observed structural element is not in contact with non-constructive elements, and is limited to L/240 in the case where the observed structural element is in contact with non-constructive elements. In the elements with FRP reinforcement, which is not susceptible to corrosion, larger crack widths may be allowed than in elements with steel reinforcement. Generally, the crack width is limited for aesthetic reasons. Thus, ACI-15 [29] and CSA-12 [30] limit the crack width to 0.5 mm for a very aggressive environment or to 0.7 mm for other conditions. Additionally, in order to prevent failure of FRP reinforcement from constant and cyclic loads due to the appearance of creep and fatigue, the stresses in the FRP reinforcement for service loads are limited. ACI-15 [29] limits the stress in GFRP reinforcement for service loads at 20% of tensile strength, while CSA-12 [30] limits this at 25%, in order to prevent failure due to creep rupture and fatigue. In Tables 4-6, the experimental loads at which midspan deflection of the beam reaches L/240, the maximal crack width reaches 0.7 mm, and the stresses in the GFRP reinforcement reach 20% of the tensile strength are given. Additionally, the percentage of service loads when the serviceability criteria are satisfied against the ultimate load for the midspan and for the middle support are also given.  
The results in Table 4 show that for the criterion of limiting the deflection at L/240, the service loads are similar for beams series 1 (46.9-50.5%) and series 2 (53.0-57.0%). It can be concluded that the poor bond strength between the GFRP reinforcement and concrete in beams series 2 does not affect the level of service load obtained by limiting the deflection. For the criterion of limiting the maximal crack widths to 0.7 mm (Table 5), the service loads differ significantly for beams series 1 (31.2-62.3%) and series 2 (16.7-24.2%). The difference in results is a direct consequence of the very good bond strength between the ribbed GFRP reinforcement and concrete for beams series 1 and the poor adhesion conditions between the wrapped GFRP reinforcement and concrete for beams series 2. For the criterion of limiting stress in the reinforcement, the results are also similar. The service loads range from 22.1% to 33.3% of the ultimate load for beams series 1 and from 28.9% to 35.6% for beams series 2 (Table 6). For all limitation criteria, with the increase of the designed moment redistribution, the level of service load decreases in relation to the ultimate load, especially for beams series 1 with ribbed bars. For the criterion of limitation of crack widths, this is primarily a consequence of the reduction in the amount of reinforcement in the middle support section due to the designed moment redistribution, which causes greater crack widths in these sections. With this finding, it is noted that for the beam G1-25, the level of service load, as a criterion for crack width limitation, is significantly different for the midspan (79.8%) and for the support (31.2%). Considering beams series 1 with ribbed bars, the level of the service load is the smallest in the case of stress limitation in the GFRP reinforcement, as presented in Tables 4-6.