Performance analysis of the ultra high performance concrete composite beam subjected to impact loads

Ultra High Performance Concrete (UHPC) has gradually become the most promising high-performance material, and has achieved good results in the field of impact and explosion protection engineering. In general, normal reinforced concrete (NC) beams subjected to impact load are prone to local punching shear failure. Although pure UHPC beams can improve their impact performance, their further application is limited by the high cost. In order to achieve the balance between impact resistance and economy, this study puts forward the design scheme of local replacement and wrapping with UHPC to improve the impact resistance of reinforced concrete beams. In this work, the different research conditions including NC beam, UHPC beam and NC-UHPC composite beam are designed, and the impact resistance of specimens is compared and analyzed. The results show that UHPC local replacement scheme can effectively avoid local punching shear failure of beams. As for the UHPC wrapping scheme, the failure mode of the beam changes from punching shear failure to bending failure. Compared with NC beams, two schemes can effectively reduce the peak displacement and residual displacement in the mid-span. The peak displacement and residual displacement in the mid-span of the UHPC local replacement beam are smaller than that of UHPC wrapping schemes, and the mid-span bearing capacity is better. In this work, it is recommended to take a local replacement length greater than 2 times the beam height to avoid local punching shear failure.