# Shear Capacity of Textile-Reinforced Concrete Slabs without Shear Reinforcement
## 4 Discussion
### Comparison to Existing Models and Current Design Provisions  
For beams and slabs with FRP-longitudinal reinforcement without shear reinforcement, engineering models and design formulas have been derived and validated by various researchers. Whether these models are directly applicable to the non-metallic grid-like carbon textile reinforcement in slabs or slab segments is discussed in this section. Due to the limited variation in key parameters such as reinforcement ratio, reinforcement ultimate strength, reinforcement modulus of elasticity, and concrete strength, no generalizable statement on transferability is possible. However, the comparison of the experimental results to predicted values enables a first assessment of the applicability of existing models and thus prepares future work. Two models and two design provisions were chosen for calculation. The model of [PERSON] et al. [46] has been developed specifically for FRP reinforcement based on a mechanical approach in combination with evaluation of an extensive database with genetic programming. An even more general (and more recent) model for steel-reinforced members by the same authors, the Compression Chord Capacity Model [27], is based on similar assumptions but differs in the calculation of the size effect factor. Here, however, the original model for FRP reinforcement has been used. The second model is the simplified shear design approach by [PERSON], [PERSON], and [PERSON] [83; 84] based on the Critical Shear Crack Theory [22; 23]. This model is currently part of the discussion for the upcoming revision of Eurocode 2 [85] and can be used for FRP reinforcement by considering the modulus of elasticity of the longitudinal reinforcement. Keeping in mind that using similar approaches towards the shear design procedures for conventional reinforcement and non-metallic reinforcement is of major interest for practice, the application of the model in this paper is justified. With the American Concrete Institute (ACI) code 440.1R-15 [54] and the Canadian Standards Association (CSA) Code S806-12 [53], American codes provide established models for shear design of FRP-reinforced concrete members. In contrast to European standardization, a longer experience for the use of FRP especially for bridges exist. Both codes follow the respective shear design tradition for reinforced concrete. In Table 5, the formulae and variables necessary for calculation of the selected models are summarized. The last column gives comments and explanations regarding how the various parameters were specifically set for prediction of the experimental results of this paper. The results of the comparison for all four models are shown in Figure 9. The mean value of the experimental to theoretical shear force ratio \(V_{\text{exp}}/V_{\text{calc}}\) is an indicator of accuracy, while the COV is used as a measure of precision. Generally, all models except ACI 440.1R-15 show promising results. The best mean value is obtained by the simplified approach based on critical shear crack theory with \(V_{\text{exp}}/V_{\text{calc}}\) = 0.95, while the CSA S806-12-model leads to the lowest COV with 18.9%. The ACI 440.1R-15 leads to conservative results, with a mean ratio \(V_{\text{exp}}/V_{\text{calc}}\) = 2.3. Furthermore, this model shows the lowest COV with 22.3%. This observation is consistent with those of other researchers, e.g., [46]. For all models, the high scatter of ultimate shear load for the three largest plate segments (C3-1-12) significantly influences the prediction results. The models cannot represent the direct strut action (tied arch action) adequately. However, these first results indicate that the prediction of shear capacity for TRC with suitable existing models for FRP reinforced concrete or TRC is possible.