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中文摘要：
基于微观力学建立的第一起裂应力准则和裂缝稳态开裂准则研发的超高韧性水泥基复合材料（英文缩写为UHTCC）在较小纤维掺量下（通常2％体积）拉应力应变曲线表现出明显的伪应变硬化特征，极限拉伸应变可高达3％～5％，极限荷载时平均裂缝宽度仅为60-80μm，实现了宏观有害裂缝向微细无害裂缝的转变，是一种具有高耐久性的新材料。使用UHTCC材料替换钢筋混凝土梁受拉区的部分混凝土，进行三组不同配筋率的UHTCC材料增强钢筋混凝土复合梁的弯曲试验，观察加载开始至破坏整个过程中承载力、变形、与钢筋变形的协调性以及裂缝开展情况的变化，并与普通钢筋混凝土梁做了对比。结果表明，同一配筋率下，在钢筋混凝土梁受拉区使用UHTCC替换部分混凝土较普通钢筋混凝土梁不仅承载力有所提高，而且能够有效地控制裂缝宽度，正常使用阶段裂缝宽度不超过0．1mm，极大提高了结构的耐久性。使用根据梁理论推导的受弯加载各阶段内力变形的解析公式计算了试验粱的弯矩-曲率以及荷载-变形曲线，与试验结果吻合很好。
英文摘要：
Based on first-cracking criterion and steady-cracking criterion constructed from the micromechanical model, ultra-high toughness cementitious composites material, abbreviated as UHTCC, is tailored even in case of low fiber volume faction, typically 2% by volume. This material is characterized by the pseudo tension strain-hardening under direct tension, and has high ultimate tensile strain capacity up to 3%-5%, and narrow crack width of only 60-80μm at ultimate tension load. These advantages allow the transform of macro harmful crack into micro harmless crack and UHTCC therefore is considered to be a new promising solution to durable structures. The present paper investigated the flexural behavior of three groups of UHTCC/RC composited beams with three different reinforcement ratios, in which concrete in the region of tension zone of RC beam is partly replaced by UHTCC. The flexural load-carrying capacity, deformation ability, deformation compatibility between steel and UHTCC along with crack development in beam during the entire loading process are examined. For comparison, the ordinary reinforced concrete beams are tested as control reference, too. The experimental results reveal that, in case of the same reinforcement ratio, RC beam strengthened with UHTCC has high flexural capacity and can efficiently control crack width to obtain high durable structures in comparison with ordinary reinforced concrete beam. Moment-curvature curves and load-mid-span displacement curves of tested UHTCC/RC composited beams are calculated using the analytical formulae developed based on beam theory and compared with the experimental measurements. A good agreement between them is found.
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