Tension Lap Splices Strengthened with Ultrahigh-Performance Fiber-Reinforced Concrete

Abstract

This paper presents the results of an experimental program undertaken for evaluating the effectiveness of ultrahigh performance fiber-reinforced concrete (UHPFRC) for strengthening deficient tension lap splices. A total of 18 full-scale beam specimens were tested. Tension reinforcement consisted of two deformed bars spliced at midspan. The strengthening technique consists of replacing normal concrete in the splice region with UHPFRC. One type of fiber concrete was used in this experimental program. It is characterized by a compressive strength of 130 MPa, a high tensile strength of 10 MPa, and ductile strain hardening characteristics in direct tension. The parameters considered were: splice length, bar diameter, repair depth, and bar relative position. To isolate the contribution of UHPFRC, no stirrups were used. The results clearly show the effectiveness of UHPFRC for strengthening deficient lap splices. Failure by splitting in the lap splice region was completely eliminated due to the high tensile strength and energy absorption capabilities of the UHPFRC used. Bond stresses that were more than twice those of normal concrete were observed. The UHPFRC ductility allows for the development of quasi-plastic tensile stresses around the reinforcing bars to resist the splitting forces. For the selected UHPFRC, this stress was evaluated at approximately 7.3 MPa, which is applicable to tensile strains of up to 0.2% before the formation of discrete cracks. Although the paper focuses on rehabilitation, the results are also applicable to new constructions. Suggestions for further research and better classification of UHPFRC for structural applications are identified.