The results of an extensive experimental program into the location of the neutral axis in cracked fiber‐reinforced concrete (FRC) are reported. In total, 74 prisms are tested in a monotonic (51 specimens) and cyclic (23 specimens) bending test in accordance with EN 14651. In the program, 13 different FRCs are considered with 9 different fiber types and dosages. A normal strength concrete with residual strength values between 1b and 2d, cf. Model Code 2010 (MC10), is considered. The deformation profile in the cracked section is measured by side‐mounted linear variable displacement transducers on the prisms, and the position of the neutral axis is calculated. The experimental results are compared against predictions of the MC10. Based on a simplified stress diagram, the MC10 predicts that the location of the neutral axis depends on the residual strength of the FRC at the serviceability limit state: increasing the strength results in a larger compressive zone and vice versa. However, the results obtained within this study do not confirm this relation. The cyclic results indicate that the neutral axis shifts upward during unloading and subsequent reloading decreases the neutral axis again to preunloading levels. Finally, for all reported FRC types, the neutral axis lies very high in the cracked section, even at very small crack mouth opening displacement values.

中文翻译：

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纤维混凝土棱镜中性轴位置的实验研究

据报道，对开裂的纤维增强混凝土（FRC）中性轴的位置进行了广泛的实验程序。根据EN 14651的规定，总共对74个棱镜进行了单调（51个样本）和循环（23个样本）弯曲测试。在该程序中，考虑了13种不同的FRC，并使用了9种不同的纤维类型和剂量。剩余强度值在1b和2d之间的普通强度混凝土，请参见。考虑使用型号代码2010（MC10）。裂纹截面的变形轮廓由侧面安装在棱镜上的线性可变位移传感器测量，并计算出中性轴的位置。将实验结果与MC10的预测进行了比较。根据简化的应力图，MC10预测中性轴的位置取决于在使用寿命极限状态下FRC的残余强度：增加强度会导致较大的压缩区域，反之亦然。然而，在这项研究中获得的结果并不能证实这种关系。循环结果表明，中性轴在卸载过程中向上移动，随后的重新加载使中性轴再次降低到卸载前的水平。最后，对于所有报告的FRC类型，即使在裂纹口张开位移值很小的情况下，中性轴也位于裂纹区域中很高。循环结果表明，中性轴在卸载过程中向上移动，随后的重新加载使中性轴再次降低到卸载前的水平。最后，对于所有报告的FRC类型，即使在裂缝口张开位移值很小的情况下，中性轴也位于裂缝区域中很高。循环结果表明，中性轴在卸载过程中向上移动，随后的重新加载使中性轴再次降低到卸载前的水平。最后，对于所有报告的FRC类型，即使在裂纹口张开位移值很小的情况下，中性轴也位于裂纹区域中很高。