Flexural performance of UHPC-encased H-shape steel beams: Experiments and theoretical analysis

To enhance the durability of steel beams and the bearing capacity of UHPC beams, this study proposes UHPC-encased H-shape steel beams, also called Structural-steel-Reinforced UHPC H-shape (SRUHPC-H) beams. Four-point bending tests were carried out on four full-scale SRUHPC-H beams. The bending failure mode and cooperative working performance of SRUHPC-H beams were analyzed, and the flexural bearing capacity and deformation performance were evaluated based on the test results. The results showed that all the specimens exhibited typical tension-controlled beam behavior, experiencing elastic stage, diffuse cracking stage, yielding stage and finally UHPC crushing. The beams satisfied the plane section assumption before yielding. The strain coordination between the internal steel plate and the external UHPC was good, and the deformation capacity was better than that of the traditional steel-reinforced concrete beam and the steel-reinforced UHPC rectangular beams. The material utilization efficiency and economy were effectively improved by the H-shaped section design. Finally, a flexural prediction method is proposed. The mean value and the root mean square error (RMSE) of the predicted-to-test ratio were 0.98 and 0.04, respectively. • A new type of UHPC-encased H-shape steel (SRUHPC-H) beam is proposed. • The SRUHPC-H beam exhibits typical tension-controlled flexural behavior. • The strain coordination between the internal steel plate and the external UHPC is good before yielding. • A flexural prediction method of SRUHPC-H beams is proposed and shown less than 8 % prediction error. • The deformation capacity of SRUHPC-H beam is better than that of the traditional SRUHPC rectangular beam.