Flexural behavior of UHPC encased steel composite beams: Experiment and numerical simulation

This paper aimed to enhance the understanding of the flexural behavior and cracking mechanism of UHPC encased steel (UES) composite beams with different section types, as well to evaluate the flexural performances compared with the traditional steel reinforced concrete beams. Three beam specimens with different concrete types (ordinary concrete and UHPC) and different beam section types (solid and hollow sections) were designed and tested. The damage mode and cracking mechanism of UES composite beams were revealed by Digital Image Correlation (DIC) technique. Then, three finite element (FE) models were developed and the validated FE models were used to parametrically investigate the flexural behavior of UES beams with different design parameters such as longitudinal tensile reinforcement ratio, inverted T-beam web and flange thickness, and UHPC compressive strength. The results reveal that the growth of concrete strength can effectively improve the flexural capacity of the UES composite beams, which was raised by 24.6 % for the UHPC composite beam compared to the C50 concrete composite beam. The removal of the upper flange plate and section hollowing had less impact on the bending performance of the UES beams. The growth of tensile reinforcement ratio and the growth of web and flange thickness of inverted T-beam can raise the flexural capacity of UES beam, while the improvement of UHPC compressive strength has small effect. This paper provides a systematic and comprehensive understanding of the flexural performance and cracking mechanism of UES beams with hollow section, which will strongly promote the cost-effective application of UHPC.