Improving the Failure Mode of Over-Reinforced Concrete Beams Using Strain-Hardening Cementitious Composites

Abstract

Over-reinforced sections fail suddenly by compression concrete crushing when their ultimate compressive strain has been exceeded but the longitudinal reinforcement strain has not yielded. This study investigates the use of cementitious repair materials for the compression side of over-reinforced concrete beams to change their failure mode to ductile failure. In this study, 11 over-reinforced concrete beams were cast (1 as a control specimen and 10 as strengthened beams). The study’s strengthening material was an ultra-high-performance strain-hardening cementitious composite (UHP-SHCC). The effect of shear connectors with the strengthening material was investigated. Meanwhile, replacement of the concrete cover, use of a welded wire mesh inside the additional layer, and concrete strength were tested. Crack pattern and failure modes were noted, and deflection behavior, failure loads, steel strains, and crack width were measured. The tests results showed that using strengthening UHP-SHCC material is a highly effective method to increase the load--carrying capacity of existing over-reinforced concrete beams, and demonstrated the contribution of the proposed technique to improving the ductility behavior of over-reinforced concrete beams.