Experimental Study and Analysis of Flexural Behavior of ECC/RC Composite Beams

Engineered cementitious composite (ECC) has ultra-high toughness and excellent crack controlling ability. A type of ECC/RC (reinforced concrete) composite beam constructed with the U-shape permanent formwork made by ECC is proposed, in order to improve the durability and mechanical performance. A full-range nonlinear analysis method for flexural behavior of ECC/RC composite beam is presented, and three interface treatments of composite beam are designed to study the flexural behavior. Results indicate that, compared with RC beam, both the load bearing capacity and ductility of composite beam are increased. Furthermore, the crack width of composite beam is less than 100 μm when the applied load is lower than 80% of the peak load. The interface treatments in ECC/RC composite beams have little effect on the flexural strength, but they affect the member ductility to a certain extent. The calculated load-displacement curves by the proposed method are shown to be consistent with the test data. Based on the method of effective moment of inertia suggested by ACI code, a simplified calculation method of deflection for ECC/RC composite beam at the serviceability limit state is proposed, and the equations for the inertia moment of the full cracked section based on the internal force equilibrium are also obtained. The predicted deflection based on the proposed simplified calculation method shows good consistence with the experimental results.