Experimental and analytical research on the flexural behavior of dismountable prefabricated composite beams with wet joint under hogging moment

Owing to the weak part of wet joint of prefabricated composite beams with full-width wet joints under hogging moment, ultra-high performance concrete (UHPC) was applied to improve the performance of wet joint interface (WI) in this study, and dismountable bolt connectors were applied to improve the assembly performance of composite beams. Totally 10 prefabricated composite beams with different concrete materials, rebar ratio and shear connector parameters were tested, for studying the failure mode, cracking behavior, concrete-steel slip (C-S slip) action and theorical study on the cracking load and ultimate flexural capacity. Two failure modes were observed, both of which are associated with the diameter of connectors. Strain response of specimens was studied, and the top surface concrete strain at WI was found higher than that at mid-span. It followed the cracking behaviors that the main cracks occurred at the position of WI. The cracking load mainly related to the material type of precast slabs and wet joint. The use of bolt connectors can delay the development of crack width to some extent, which can be contributed to the higher C-S slip. Through theorical study, the cracking load can be calculated through transformed-section method, showing small error (0.55 % to 10.65 %) to the experimental value. Considering the effect of performance of connectors and shear connection degree on flexural behavior of composite beams, a prediction calculation equation for ultimate flexural capacity was proposed and was in good agreement with the experimental results.