FLEXURAL BEHAVIOR AND CAPACITY ANALYSIS OF RC BEAMS WITH PERMANENT UHPC FORMWORK

Four reinforced concrete (RC) beams with pre-fabricated permanent ultra-high performance concrete (UHPC) formworks and two RC beams were tested for flexural behavior. The reinforcement ratio and thickness of concrete cover were varied. The mechanical properties of pre-fabricated UHPC formwork RC beams and the interface bonding performance between UHPC formwork and post-cast-in-place concrete were mainly studied. The results show that when the load reached the peak value, no slip was observed on the interface between the prefabricated UHPC formwork and the post-cast-in-place concrete. The interface between the pre-fabricated UHPC formwork and the post-cast-in-situ concrete was slightly debonded after the peak load. Cracking load of prefabricated UHPC formwork RC beams increased by approximately 50%, and the yield load and ultimate load increased by about 10%, compared to that of standard RC beams. A flexural capacity calculation model of the pre-fabricated UHPC formwork RC beams was established based on the section balance condition, the assumption of plane section and the constitutive relation amongst UHPC, plain concrete and the reinforcement. The calculation results of flexural capacity agreed well with the experimental results.