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中文摘要：
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。
英文摘要：
Through pouring ultra high toughness cementitious composite（UHTCC） at flexural side of existing conventional concrete beam with different depths,fixed cross section composite beams were made.Integral working performance combined with two materials by four-point bending test and capacities of UHTCC layer for separating cracks and restricting crack propagation were studied.Using restricted concrete tensile constitutive model,the ultimate bearing capacities in process of integral force of composite beam with different stages were calculated by plane-section assumption method.The results show that UHTCC layer can control crack generation and propagation and can separate single macro concrete crack into multiple fine cracks effectively through crack-bridging and stress transform of fibers.UHTCC layers in composite beam can not only increase the bearing capacity,but also control the concrete crack width and strengthen the integral ductility of beam.The mid-span deflection and ultimate flexural strength of composite beams increase with increasing of the proportion of UHTCC layer at side of tensile.The influence of UHTCC layer on the flexural strength of beams in the initial test stage declines with increasing of concrete strength grade,but the whole toughness of composite beam is still improved obviously.The calculated values of ultimate bearing capacity agree well with measured values.
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