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对不同厚度的既有普通混凝土梁体受弯一侧浇筑超高韧性水泥基复合材料(UHTCC)制成定截面复合梁,通过四点弯曲试验对2种材料结合后的整体工作性能,以及UHTCC层作为外浇层对表面裂缝的分散和限制能力进行试验研究。通过平截面假定法和平衡方程,采用受约束的混凝土受拉本构模型,推导计算了复合梁整体受力过程中不同阶段的极限承载力。结果表明:通过纤维的桥联和应力传递作用,UHTCC层能有效控制裂缝的生成和扩展,并将上层混凝土中出现的单条宽裂缝分散成多条细密裂缝;UHTCC层的加入提高了复合梁的承载能力,限制了混凝土裂缝的开展,增强了整体延性;受拉一侧UHTCC所占的比例越大,复合梁中点挠度越大,极限弯曲强度越高;混凝土强度等级越高,UHTCC层对复合梁前期强度影响越小,但后期整体韧性改善依旧显著;极限承载力计算值与实测值符合较好。
Through the four-point bending test, the overall workability of two kinds of materials after the combination of UHTCC and UHTCC was cast on the bending side of conventional common concrete beams with different thicknesses, and the UHTCC Layer as an overcast layer on the surface crack dispersion and limiting ability to conduct experimental study. Through the constitutive equation of the cross-section and the equilibrium equation, the constrained concrete tension model is adopted and the ultimate bearing capacity of the composite beam in different stages is deduced and calculated. The results show that the UHTCC layer can effectively control the formation and propagation of cracks through the bridging and stress transmission of fibers, and disperse a single wide crack in the upper concrete into multiple fine cracks. The addition of UHTCC layer improves the composite beam Bearing capacity, which limits the development of concrete cracks and enhances the overall ductility. The greater the proportion of UHTCC on the tension side, the greater the midpoint deflection of composite beam, the higher the ultimate flexural strength. The higher the concrete strength level, The effect of early strength of composite beam is smaller, but the improvement of overall toughness is still significant. The calculated value of ultimate bearing strength is in good agreement with the measured value.