Experimental study on shear behaviors of segmented cast ultra-high-performance fiber-reinforced concrete (UHPFRC) beams with/out stirrups
Zheng Feng, Phoebe D. Lu, Lu Ke, Chuanxi Li, Wangchen Zhang, Doo‐Yeol Yoo
Abstract
Due to the limitations of concrete mixing, transportation and maintenance, large span ultra-high-performance fibre-reinforced concrete (UHPFRC) bridges inevitably need to be cast in segments, resulting in weakly stressed longitudinal joints between adjacent segments. However, current research on the structural performance of segmented cast UHPFRC (SC-UHPFRC) bridges is insufficient to support the application of large span UHPFRC bridges. Therefore, to investigate the shear performance of SC-UHPFRC beams, 6 SC-UHPFRC beams and 3 monolithic cast UHPFRC (MC-UHPFRC) control beams under bending and shear loads were carried out. The study variables cast methods, shear span-to-depth ratios (0.8, 1.6 and 2.4), with/without stirrups and fibre volume fractions (2.0 % and 3.0 %). The experimental results indicated that the failure modes of SC-UHPFRC beams mainly included direct shear failure, diagonal shear failure, flexural-shear failure, and flexural failure, depending on the shear span-to-depth ratio and stirrups. As the shear span-to-depth ratio decreased from 2.4 to 0.8, the cracking at the cold joints in the SC-UHPFRC beam became progressively more severe. When the shear span-to-depth ratio of the SC-UHPFRC beams without stirrups increased from 0.8 to 1.6 and 2.4, the ultimate load decreased by 49.5 % and 64.1 %, respectively. The cold joint interface became a critical factor influencing the failure mode and shear strength of SC-UHPFRC beams when the shear span-to-depth ratio was lower than 1.6. The addition of stirrups and an increase in fibre volume fraction could improve the shear performance of SC-UHPFRC beams, potentially resulting in more flexural damage. Additionally, a modified shear capacity model for SC-UHPFRC beams was developed based on the shear capacity model for MC-UHPFRC beams and taking into account the reduction in shear strength at cold joints in UHPFRC beams . The calculated results of this model were in excellent agreement with the experimental results.