目的目的为研究负弯矩作用下部分充填式窄幅钢箱-UHPC(ultra-highperformanceconcrete,UHPC)组合梁的抗弯性能,采用反向集中力对9根不同参数的试验梁进行静载试验。方法方法研究部分充填式窄幅钢箱-UHPC组合梁在反向集中力作用下的受力过程、应变行为、刚度和抗裂性,明确各参数在提升试验梁力学性能方面的贡献程度,并将考虑界面滑移和翼板开裂因素的理论挠度与试验结果进行比较和验证。结果结果部分充填式窄幅钢箱-UHPC组合梁处于整体弹性阶段时刚度最高,翼板开裂后刚度略有下降,钢箱下翼缘局部受压屈服时,跨中翼板上形成多条贯通裂缝,极限承载力阶段,承载力未明显下降。与部分充填式窄幅钢箱-NC(ordinaryconcrete,NC)组合梁和窄幅钢箱-UHPC组合梁相比,随着钢纤维掺量、配筋率和相对充填高度增加,部分充填式窄幅钢箱-UHPC组合梁的极限承载力、正常使用和承载能力极限状态的最大刚度分别提高57%,25%,21%,裂缝宽度为0.05,0.10,0.20mm时,对应的最大荷载分别提高155%,266%,100%。结论结论部分充填式窄幅钢箱-UHPC组合梁刚度大,抗裂性能好,承载力高。现行规范计算负弯矩作用下组合梁挠度过于保守,考虑负弯矩作用下组合梁滑移影响的有效惯性矩法计算试验梁挠度较为准确。

Objectives This study investigates the flexural performance of partially-filled narrow steel box-UHPC (ultra-high performance concrete) composite beams under negative bending moment, static load tests were conducted on nine composite beams with varying steel fiber contents, reinforcement ratios, and relative filling heights under reverse concentrated force. Methods The contributions of different parameters to the enhancement of the beams’ mechanical properties were quantitatively assessed. Additionally, theo⁃retical deflection calculations, which take into account interface slip and flange cracking, were compared and validated against experimental results. Results The stiffness of the partially-filled narrow steel box-UHPC composite beams reached its peak in the overall elastic stage. After flange cracking, the stiffness slightly decreased. When the lower flange of the steel box locally yielded under compression, multiple through-cracks formed at mid-span. At the ultimate load stage, there was no significant reduction in bearing capacity. Compared with partially-filled narrow steel box-Normal Concrete (NC) composite beams and nar⁃row steel box-UHPC composite beams, as the parameters increased, the ultimate bearing capacity, stiff⁃ness at the serviceability limit state, and stiffness at the ultimate limit state of the partially-filled narrow steel box-UHPC composite beam increased by up to 57%, 25%, and 21%,  respectively. The loads corre⁃sponding to crack widths of 0.05 mm, 0.1 mm, and 0.2 mm increased by up to 155%, 266%, and 100%, respectively. Conclusions The partially-filled narrow steel box-UHPC composite beam exhibits high stiff⁃ness, excellent crack resistance, and superior bearing capacity. The current codes for calculating the de⁃flection of composite beams under negative moments are overly conservative. In contrast, the effective mo⁃ment of inertia method, which considers the influence of interface slip in composite beams under negative moments, provides more accurate calculations of the deflection of the test beams.