Shear strengthening of reinforced concrete beams using ultra high performance cementitious (UHPC) materials

Abstract

Existing concrete structures are usually under-reinforced when it comes to shear design requirements. Shear failure is a brittle process. Ultra High Performance Cement (UHPC) is a new emerging technique used for reinforcement of built concrete structures. UHPC is a type of concrete that has advanced mechanical and durability properties. Few studies exist concerning the different aspects of this reinforcement technique.This research emphasizes on the effect of using UHPC plates on the shear strength of concrete beams. For this purpose, reinforcement of concrete beams using two configurations of UHPC was studied: continuous strip of UHPC and discontinuous strips of UHPC on the shear critical areas of the beam. The behavior of the two configurations is compared to the behavior of a non-reinforced beam and an internally shear reinforced beam. The UHPC used contains 2% of steel fibers per mass UHPC mortar. The flexural strength and compressive strength of 108.09 MPa at 28 days. Additionally, UHPC reinforced concrete beams experienced an increase in strength capacity of about 50% for continuous strip and 36% for discontinuous strips to reach an ultimate maximum load of 104.9 KN and 80.56 KN, respectively compared to 51.48 KN for the non-reinforced beam.The results are close to the results of an internally reinforced beam using stirrups, which reached a load of 91.36 KN. On the other hand,the ductility of the beams was improved in all types of reinforcement but the best improvement in ductility was observed for the beam reinforced uding discontinuous UHPC strips