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

Area of Science:

• Civil Engineering
• Structural Engineering
• Materials Science

Background:

• The construction industry increasingly uses high-strength steel (HSS) reinforcement (yield strength > 600 MPa).
• Accurate prediction of tension stiffening is crucial for serviceability limit states like deflection and crack width in reinforced concrete (RC) structures.

Purpose of the Study:

• To evaluate the predictive accuracy of current models for curvature in RC beams utilizing HSS bars.
• To assess the phenomenon of tension stiffening in RC beams with HSS reinforcement.

Main Methods:

• Compared three design code methods (Eurocode 2, ACI 318-14, ACI 318-19) and two analytical models (Bischoff, Kaklauskas and Sokolov).
• Utilized experimental data from one tested RC beam with HSS bars and 63 others from published literature.
• Performed inverse analysis on experimental moment-curvature data to determine tension stiffening effects.

Main Results:

• Tension stiffening effects were evident up to approximately three times the cracking bending moment (3*Mcr).
• Statistical analysis revealed normalized curvature predictions (κth/κexp) ranging from 0.81 to 0.99 across different models and stress levels.
• Design code models generally underestimated the curvature of RC beams with HSS.

Conclusions:

• Existing design codes require refinement for accurately predicting curvature in RC beams with HSS.
• The study provides valuable insights into tension stiffening behavior, crucial for the design of modern concrete structures with HSS.