目的目的为解决超高性能混凝土(ultra-highperformanceconcrete,UHPC)在加固钢筋混凝土方柱中与基础的脱黏问题,方法方法在节点加强下采用UHPC对钢筋混凝土方柱进行加固。为验证该加固方法的有效性,设计并制作4个试件,以加固与否、不同轴压比(0.2,0.4)为参数,对各试件的延性性能、累计耗能、峰值承载力等抗震性能指标进行分析。结果结果试验结果表明,UHPC节点加强加固柱的延性系数、累计耗能最高提升了15.7%,76.4%,承载力最大提升了37.6%,并且加固柱滞回曲线的捏拢效应有所改善,这是因为:一方面,采用节点加强可以增大UHPC加固层与基础顶面的黏结应力,使UHPC加固层与核心混凝土具有非常良好的协同工作作用;另一方面,UHPC加固层可以限制混凝土开裂和塑性铰区纵筋屈曲,从而提高塑性铰区的转动能力。随着轴压比提高,试件承载力呈上升趋势,但延性性能和累计耗能均有所下降,这是因为UHPC中的钢纤维具有桥联作用,抑制了水泥基体裂缝的发展,使UHPC加固层剥落不严重,对高轴压比试件的破坏形态改善较为明显。最后提出一种基于平截面假定的UHPC节点加强加固柱的压弯承载力计算方法,计算结果与试验结果的比值均大于0.85,具有较高的精度,验证了该计算方法的合理性。结论结论研究成果可为节点加强下UHPC加固RC方柱的实际工程应用及设计提供试验依据和理论参考。

Objectives To address the problem of debonding between ultra-high performance concrete (UHPC) and reinforced concrete (RC) square columns in strengthened structures, Methods a method of strengthening the RC square columns with UHPC under node reinforcement was proposed. To verify the ef‐fectiveness of this reinforcement method, four specimens were designed and fabricated. The seismic perfor‐mance indicators, such as ductility, cumulative energy dissipation, and peak load-carrying capacity were analyzed based on whether the columns were reinforced and different axial compression ratios (0.2,0.4). Results The test results showed that the ductility coefficient and cumulative energy dissipation of UHPC node reinforcment columns increased by up to 15.7% and 76.4%, respectively, and the peak load-carrying capacity increased by up to 34.5%. The pinching effect of the hysteresis curve of the reinforced columns was improved. This improvement was due to the node reinforcement increasing the bonding stress between the UHPC reinforcement layer and the foundation base, enabling excellent synergy between the UHPC rein‐forcement layer and the core concrete. Additionally, the UHPC reinforcement layer could restrict the crack‐ing of concrete and the buckling of longitudinal reinforcement in the plastic hinge zone, thereby improving the rotational capacity of the plastic hinge zone. With the increase of axial compression ratio, the load-carrying capacity of the specimens showed an upward trend,but both ductility and cumulative energy dissi‐pation decreased. This was because the steel fibers in UHPC acted as bridges, inhibiting the development of cracks in the cement matrix and reducing the severity of delamination in the UHPC reinforcement layer, resulting in more apparent improvement in the failure mode of high axial compression ratio specimens. Fi‐nally, a calculation method for the flexural bearing capacity of UHPC reinforced columns based on the as‐sumption of plane section is proposed. The ratio of the calculated results to the test results was greater than 0.85, indicating high accuracy and validating the rationality of this calculation method. Conclusions The re‐search findings can provide an experimental basis and theoretical reference for the practical engineering ap‐plication and design of UHPC reinforced RC columns under node reinforcement.