Evaluation of Deflection Prediction Models for RC Beams with High-Strength Steel Reinforcement

The modern construction industry has witnessed a marked shift towards the utilization of high-strength steel reinforcement, exhibiting yield strengths exceeding 600 MPa in reinforced concrete structures. Tension stiffening is a critical factor for accurate prediction of deflection and crack width. The current study evaluates the accuracy of state-of-the-art models in predicting curvature in Reinforced Concrete (RC) beams reinforced with high-strength steel (HSS) bars. This study employed three design code methods (Eurocode 2, ACI 318-14, and ACI 318-19) and two other models: the Bischoff model and Kaklauskas and Sokolov's model. An RC beam with HSS bars was tested, and experimental data on another 63 RC beams reinforced with HSS rebars were collected from various published studies. The test data ranged in various geometrical and material characteristics and were evaluated across a wide range of steel stress intervals. An inverse analysis was carried out to calculate the resultant internal force of tensile concrete (tension stiffening) from the experimental moment-curvature diagram. The inverse analysis demonstrated that the fully cracked RC section reached stiffness at a bending moment of about 3M_cr, where M_cr is the cracking bending moment predicted according to the EC2 design code. Statistical analysis showed that the predicted mean normalized curvature (κ_th/κ_exp) across several reinforcement stress levels ranged from 0.99 to 0.81 for different models. The design codes tend to underestimate curvature. The coefficients of variation ranged between 17.8% and 24.9% for different models.