超高韧性水泥基复合材料增强普通混凝土复合梁弯曲性能的理论分析

Theoretical analysis of flexural performance of plain concrete composite beams strengthened with ultrahigh toughness cementitious composite

假定不考虑普通混凝土起裂后粘聚软化对承载力的贡献,理论研究了超高韧性水泥基复合材料UHTCC增强普通混凝土复合梁的弯曲性能。使用三组UHTCC/混凝土复合梁四点弯曲试验数据验证了理论公式,并对UHTCC增强层厚度、混凝土抗压强度以及UHTCC的拉应力应变控制参数对复合梁弯曲承载力和最小UHTCC层厚度的影响进行了分析。结果表明,最小UHTCC层厚度与梁高的比值不随梁高的增加而变化,在复合梁几何尺寸及UHTCC性能保持不变的情况下,随着混凝土抗压强度的增加,UHTCC层的最小厚度增加,且发生受压破坏的复合梁的极限承载力亦增加;在复合梁几何尺寸及混凝土强度相同条件下,UHTCC材料开裂后的刚度和强度对UHTCC层最小厚度影响比较显著,应变能力对承载力-梁底拉应变曲线没有影响,复合梁的承载力随着开裂强度和极限强度的增加而增大。

A theoretical investigation on the flexural performance of UHTCC/concrete composite beams is presented. The contribution of the tension softening cohesive force at the crack of concrete to the load-carrying capacity of the composite beams was not taken into account. Four-point bending experimental results of three sets of UHTCC/Concrete composite beams were employed to validate the theoretical analysis. A parametric study was carried out, including parameters such as the UHTCC layer thickness, the compressive strength of concrete as well as the tension control parameters of UHTCC, to get a clear understanding of the degree of the influence of various parameters on the flexural performance and the minimum UHTCC layer thickness of the composite beams. The results revealed that （ 1 ） the depths of composite beams did not infuence the ratio of the minimum thickness of UHTCC layer to depth; （2） when beam size and UHTCC are identical, the minimum thickness of UHTCC and the ultimate flexural capacity of the beams in compression failure mode increased as the compressive strength of concrete increased; and （3） when the size and the concrete are identical, the stiffness after cracking and the tensile strength of UHTCC more significantly affected the minimum depth of UHTCC layer. The curves of fexural load-carrying capacity vs. tensile strain at the bottom of the beams were not affected by the tensile strain of UHTCC, but the flexural load-carrying capacity of the beams increased with increases in first cracking tensile strength and ultimate tensile strength.