负弯矩区部分充填混凝土对窄幅钢箱-混凝土组合梁受力性能影响试验研究

为了研究充填混凝土对窄幅钢箱-混凝土组合梁负弯矩区的荷载-挠度特征、截面应变分布、抗弯刚度、钢箱梁的约束机理以及承载能力的影响，对5根部分充填混凝土窄幅钢箱-混凝土简支组合梁试件和1根全充填混凝土试件进行了静力加载试验。试验结果表明：在负弯矩作用下，配筋率和剪力连接程度对窄幅钢箱-混凝土组合梁的受力性能影响显著，配筋率从1%增加到2%，承载力提高22%；剪力连接度从0.75增加到1.25，承载力提高13%。半充填和全充填混凝土对窄幅钢箱-混凝土组合梁试件的承载力和刚度影响很小。充填混凝土对钢箱梁的屈曲约束作用明显，所有试件最终破坏时均未发生内凹屈曲。由于充填混凝土有效地限制钢箱变形，从而提高了组合梁的承载力和结构的稳定性。基于简化塑性理论提出了部分充填混凝土窄幅钢箱-混凝土组合梁的承载力计算方法，且计算值与试验值吻合较好。

Experimental investigation effect of partially-filled concrete on mechanical behavior of narrow-width steel box concrete composite beam in negative moment region

In order to investigate the effects of the filled concrete on the bending behaviors of narrow width steel box concrete composite beams, such as the load-deflection characteristics, the strain distribution along the height of composite section, the composite sectional flexural stiffness, the confinement mechanism to steel box beam in compression and the ultimate strength of the structure, five partially-filled concrete specimens and one fully-filled concrete specimens were tested under static loading. The experimental result indicates that under negative moment, the reinforcement ratio and the degree of shear connection have a significant effect on the mechanical behavior of the narrow-width steel box concrete composite beam. The bearing capacity increases by 22% with the reinforcement ratio increasing from 1% to 2%.The bearing capacity increases by 13% with the increasing of shear connection degree from 0.75 to 1.25. Both the partially-filled and fully-filled concrete have negligible impact on the bearing capacity and rigidity, but affect the buckling of specimens greatly, as a result, no steel box girder of all specimens encounters concave buckling before ultimate failure. Meanwhile, filled concrete can limit the structure deformation of steel box girder effectively and enhance the bearing capacity of negative bending moment region and the stability of the structure. The method to calculate the bending capability of partially-filled concrete narrow-width steel box concrete composite beam was proposed, the calculated values agreed well with the experimental results.