中文摘要：

为了研究混掺纤维对超高性能混凝土（UHPC）的增韧效果,通过161个三点弯曲梁的断裂试验,测定了4种纤维和不同掺量下各UHPC试件的载荷-裂口张开位移（CMOD）曲线和载荷-挠度曲线。将素UHPC峰值载荷对应的CMOD视为混杂纤维增强UHPC的初裂CMOD值,基于载荷-CMOD曲线提出了等效断裂韧度的韧性评价方法,该方法具有明确的物理含义,可用于分析混掺纤维品种和掺量对UHPC断裂韧性的影响规律。研究发现：在小变形（小于50倍素UHPC峰值载荷对应的CMOD值）时,UHPC韧性取决于钢纤维的掺率;粗合成纤维主要在中等变形和大变形阶段（大于50倍素UHPC峰值载荷对应的CMOD值）发挥其增韧效用。

英文摘要：

In order to research the toughness characteristics of hybrid fiber on ultra-high performance concrete （UHPC）,161 specimens of three-point bending beam fracture testing of UHPC reinforced with four type fibers and various contents have been conducted.The load-crack mouth open displacement （CMOD）curves and load-deflection curves were measured.We took the peak-load CMOD of plain UHPC as the reference initial CMOD value of hybrid fibers reinforced UHPC.Based on the load-CMOD curves,a characterization method of equivalent fracture tough-ness was proposed.This new method has clear physical meaning,and unveils the influence rule of hybrid fibers type and contents to fracture toughness of UHPC.The research shows that the toughness of UHPC depends on the con-tent of steel fiber in small deformation stage （less than the 50 times CMOD value of plain UHPC at peak load）and macro-synthetic fiber plays toughening effect in middle deformation and large deformation stage （larger than the 50 times CMOD value of plain UHPC at peak load）.