PSI - Issue 42

Rami A. Hawileh et al. / Procedia Structural Integrity 42 (2022) 1198–1205 Hawileh et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. Ratio of V ( exp ) to V ( pred ) for: (a) Specimens without stirrups; (b) Specimens with stirrups.

It can be clearly indicated from Table 2 and Fig. 1 that all shear design provisions significantly underestimated the capacity of RC T-sections, where the average ratio of experimental to predicted shear values for all the codes was above 1.0 (in the range of 1.9 – 3.89). The most conservative predictions were provided by the ACI318-19 (Eq. 3), BS8110, and Eurocode2, with mean ratios of V ( exp ) to V ( pred ) of 3.58, 3.55, and 3.89, respectively, and a COV value of 62% for all codes. The CSA23.3-04 shear design guidelines also resulted in conservative predictions; however, its predictions were the most accurate with lowest value of V ( exp ) to V ( pred ) ratio of 1.9 and SD and COV of 0.7 and 37%, respectively. It can be also indicated from Fig. 1 that the shear predictions of the specimens that did not include steel stirrups were highly underestimated and more conservative than the specimens with steel stirrups. For example, the ratio of experimental to predicted shear capacity reached almost 8.0 for the ACI318-19 (Eq. 3), BS8110, and Eurocode in the beams without steel stirrups. On the contrary, the ratio of experimental to predicted shear capacity did not exceed the value of 4.5 for the specimens with steel stirrups. As for the three design models that were developed to predict the shear capacity of T-sections, it can be seen from Table 2 and Fig. 1 that Zararis et al. (2006) provided the most accurate predictions to the shear capacity of T-beams overall. Particularly, the average ratio of experimental to predicted shear capacity is 1.45, with SD and COV values of 0.54 and 37%, respectively. The accuracy of Zararis et al. (2006) model comes from accounting for the whole area of the T-beam and determining an effective width suitable for predicting the shear strength of T-beams. Following that, Ramadan et al. (2022) predictions also provided close predictions to the shear capacity of RC T-beams (average ratio of V ( exp ) to V ( pred ) = 1.62). However, some of the predicted values were overestimated and unsafe (minimum of 0.56). This is due to the inclusion of shear stirrups in the flange and web in the equations developed by Ramadan et al. (2022), which substantially increased the predicted values. Finally, although Thamrin et al. (2016) equation was developed to predict the shear capacity of T-beams without internal stirrups, the equation failed to estimate the true capacity of the T-beams and provided the most conservative results. In particular, the mean ratio of V ( exp ) to V ( pred ) was the highest between the three models (4.67) with COV of 52%. It can be concluded that the flange contribution to shear capacity is significant and should not be neglected in determining the shear strength of the section. Most of the current design guidelines failed to estimate the true shear capacity of the T-beams due to ruling out the flange contribution. Despite that, the most accurate and safe shear design model was provided by the Canadian Standards Association (CSA 23.3-04). With respect to the models proposed in the literature, the model presented by Zararis et al. (2006) provided close estimates to the shear capacity of RC T beams and could be safely implemented to design RC T-beams in shear. It should be noted that the results are based on the experimental database chosen in this study. It is recommended in future studies to expand the database to include various T-beam dimensions (geometry) and reinforcement detailing.