After several decades of research studies, design rules for fiber reinforced concrete (FRC) are now available for several structural elements. Starting from standard tests, it is possible to determine design parameters and constitutive laws to perform simplified sectional verifications and/or numerical analyses. However, one of the main issues still open is represented by the fiber orientation in the real structure that could be different from the one present in standard tests. For this reason, building codes take into account orientation factors to modify the standard material properties. The present paper aims to shed some new lights on the effects of the orientation of steel and macro-synthetic fibers on the local variability of FRC residual strength properties in slabs made with two concretes: Vibrated (slump of 80 ± 20 mm, V-FRC) and self-compacting concrete (slump flow diameter of 700 ± 50 mm, SC-FRC). In V-FRC slabs, the orientation of polymer fibers was more influenced by pouring and compaction process compared to steel ones. In SC-FRC slabs, the flow and wall effects resulted more significant when long steel fibers were used. The post-cracking performances locally determined in different points of slabs were compared against the ones obtained on standard beams as well. Finally, the global response of these slabs was numerically studied by considering two different support configurations: simply-supported slabs and slabs on grade.

中文翻译：

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纤维取向对纤维增强混凝土板性能的影响

经过几十年的研究，纤维增强混凝土 (FRC) 的设计规则现已可用于多种结构元素。从标准测试开始，可以确定设计参数和本构法则，以执行简化的截面验证和/或数值分析。然而，仍然存在的主要问题之一是实际结构中的纤维取向，这可能与标准测试中存在的取向不同。出于这个原因，建筑规范考虑了方向因素来修改标准材料属性。本论文旨在阐明钢和宏观合成纤维的取向对由两种混凝土制成的板中 FRC 残余强度特性的局部变异性的影响：振动（坍落度为 80 ± 20 毫米，V-FRC）和自密实混凝土（坍落度流动直径为 700 ± 50 毫米，SC-FRC）。在 V-FRC 板中，与钢相比，聚合物纤维的取向受浇注和压实过程的影响更大。在 SC-FRC 板中，当使用长钢纤维时，流动和壁面效应更为显着。将在板坯不同点局部确定的开裂后性能与在标准梁上获得的性能进行比较。最后，通过考虑两种不同的支撑配置对这些板的整体响应进行了数值研究：简支板和地面板。当使用长钢纤维时，流动和壁效应更显着。将在板坯不同点局部确定的开裂后性能与在标准梁上获得的性能进行比较。最后，通过考虑两种不同的支撑配置对这些板的整体响应进行了数值研究：简支板和地面板。当使用长钢纤维时，流动和壁效应更显着。将在板坯不同点局部确定的开裂后性能与在标准梁上获得的性能进行比较。最后，通过考虑两种不同的支撑配置对这些板的整体响应进行了数值研究：简支板和地面板。