Flexural Study on UHPC–Steel Composite Beams with Joints under Negative Bending Moment

Abstract This research aims to experimentally investigate the flexural behavior of ultra-high-performance concrete (UHPC)–steel composite beams with joints under a negative bending moment in order for the results to be used in the analysis and design of UHPC flange plates in composite beams. Flexural tests were conducted to study three relevant parameters, slab mechanical properties, with/without UHPC joints at the closure strip, and UHPC joint configurations, which might affect the composite beam performance under the negative bending moment. The experimental results showed that steel–UHPC composite beams presented a better mechanical performance in terms of loading carrying capacity and controlling of crack width. Moreover, the existence of joints influences the cracking load and cracking position, leading to different crack distribution. Also, the result demonstrates the contribution of the joint configuration to the cracking development and suggests that sufficient enhancement in the flexural performance under negative moments could be achieved for UHPC–UHPC connections with changing the joint shape. However, the difference in the joint configurations did not significantly influence the yield load and ultimate load. This study may provide an understanding of the mechanical behavior of this emerging UHPC–steel composite beam with and without transverse joints under a negative bending moment.