基于纤维取向分布的应变硬化超高性能混凝土薄层抗拉性能

Tensile Response of Strain-Hardening Ultra-High Performance Fiber Concrete Thin Layer Based on Fiber Orientation Distribution

采用电磁无损检测分析自由流动浇筑的应变硬化超高性能混凝土(SH-UHPC)薄板内纤维取向分布,对沿垂直流动方向切割的试件进行直接拉伸试验(DTT)、四点弯曲试验(4PBT)及反分析。结果表明:在水平自由流动状态下,SH-UHPC薄层中纤维趋于垂直流动方向分布;SH-UHPC薄板内抗拉性能(非弹性段)波动大,主要由于纤维取向随着流动距离而不断变化;相比于4PBT,DTT能够更直接、更全面且更准确的得到SH-UHPC的抗拉性能。此外,基于试验及统计数据分析表明,SH-UHPC薄板中(90°方向)抗拉强度修正系数K_(f)=1.12,低于法国AFGC的推荐值;极限应变修正系数K_(ε)=1.25。

The distribution of fiber orientation in strain-hardening ultrahigh performance concrete(SH-UHPC) thin slab was measured by a non-destructive test(NDT) method using a magnetic probe. Afterwards, the dumbbell specimens and rectangular plates were extracted orthotopically along the flowing direction of fresh mixture. The direct tensile test(DTT), 4-point bending test(4 PBT) and inverse analysis were then conducted. The results indicate that the fibers tend to align perpendicularly toward the flow direction of fresh mixture in SH-UHPC thin layer under horizontal free-flow condition. The tensile response(inelastic part) of SH-UHPC ranges widely in thin slab, mainly due to the continuous change of fiber orientation along the flowing direction. Compared with 4 PBT,DTT can directly, comprehensively, and accurately reflect the tensile response of SH-UHPC in thin slab. In addition, the correction factor for tensile strength(i.e., K_(f)=1.12) in thin slab is less than the recommended value in AFGC standard, and the correction factor for ultimate strain K_(ε) in thin slab is 1.25 based on the experimental results and available data from the corresponding literature.