Flexural Ductility and Strength in Hybrid FRP-Steel RC Beams

Area of Science:

• Civil Engineering
• Materials Science
• Structural Engineering

Background:

• Hybrid beams combine fiber-reinforced polymer (FRP) and steel reinforcement within concrete structures.
• Understanding the mechanical behavior of these hybrid beams is crucial for optimizing structural design and performance.

Purpose of the Study:

• To investigate the behavior of hybrid FRP-steel-reinforced concrete (RC) beams using 3D finite element models.
• To analyze the influence of FRP type, reinforcement ratios, and concrete strength on beam performance.
• To develop a predictive model for FRP stress at the ultimate state.

Main Methods:

• Utilized three-dimensional finite element modeling to simulate hybrid FRP-steel-RC beams.
• Systematically varied parameters: FRP type, FRP bar ratio (ρf), FRP to total reinforcement ratio (ρf/ρt), and concrete strength.
• Employed an energy ductility index to quantitatively assess structural ductility.

Main Results:

• Investigated parameters had limited effect on cracking moment but significantly impacted yield and ultimate moments.
• Increasing ρf/ρt decreased yield moment (up to 44.34%), while increasing ρf enhanced yield moment (up to 50.63%).
• Higher concrete strength increased ultimate moment (up to 38.46%); energy ductility index was lower than conventional index.

Conclusions:

• A semi-empirical formula was proposed to estimate FRP bar stress at the ultimate state of hybrid beams.
• The proposed formula demonstrated good agreement with experimental data, indicating high applicability and reliability.
• The study provides valuable insights into the structural behavior and design optimization of hybrid FRP-steel-RC beams.