Cracking Performance in the Hogging-Moment Regions of Natural Curing Steel–UHPC and Steel–UHTCC Continuous Composite Beams

Abstract

High-performance concretes without steam curing have great potential to improve crack resistance in the hogging-moment regions of continuous steel–concrete composite beams. This paper conducts experiments to investigate the cracking resistance of hogging-moment regions of prefabricated composite beams consisting of steel–NSCs (normal-strength concretes), natural curing steel–UHPCs (ultrahigh performance concretes), or steel–UHTCCs (ultrahigh toughness cementitious composites). The tensile strengths of natural curing UHPCs and UHTCCs are first measured because the concretes are usually in the tensile state in hogging-moment regions. Flexural tests are then conducted to investigate several important parameters of steel–NSC/–UHPC/–UHTCC composite beams: deflections, initial cracking loads, crack propagation, interlayer slips, and flexural bearing capacity. It is demonstrated that relative to traditional composite beams, steel–UHPC composite beams without steam curing can effectively improve the hogging-moment bending performance such as increasing cracking load, reducing interfacial slips, and concrete slab crack width. Moreover, it is found that although the steel–UHTCC composite beams are not as good as the steel–UHPC composite beams in terms of initial cracking loads but have better performance in controlling crack widths and lengths. The effect of prestressing on steel–UHPC composite beams under hogging moment is also studied and demonstrated to be influential in further increasing the cracking performance in hogging-moment regions.