This paper attempts to investigate the mechanical behavior of ultra-high-performance concrete (UHPC) under combined tensile and bending action. For this purpose, a total of 72 specimens were tested under axial tension, pure bending, and eccentric tension loads, respectively. The test parameters included the steel fiber content (0 %, 1 %, 2 %, and 3 %) and eccentricity ratio (0, 0.1, 0.2, 0.4, 0.8, and ∞). It was found that all the specimens failed due to crack localization. The stresses and strains at cracking, peak, and ultimate load increased as the eccentricity ratio and steel fiber content rose. For specimens with a higher steel fiber content, the eccentricity ratio's effects on cracking and peak strength were more pronounced. For specimens with a commonly used fiber content of 2 %, specifically, cracking and peak strength increased by 29 % and 63 %, respectively, as the eccentricity ratio rose from 0.1 to 0.8. With the aid of full-field measurement on the specimen surface using digital image correlation, the fiber bridging mechanism of UHPC under combined tensile and bending loads was discussed. Then, a calculating method for determining the cracking load was proposed by introducing the plastic influence coefficient, which depended on the eccentricity ratio and steel fiber content. Finally, a unified approach for predicting the coupled strength of UHPC under combined tension and bending action was derived, and its robust applicability was verified through a database collected from the available literature.

中文翻译：

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超高性能混凝土在拉伸和弯曲联合作用下的性能

本文试图研究超高性能混凝土（UHPC）在拉伸和弯曲联合作用下的力学行为。为此，总共 72 个样本分别在轴向拉伸、纯弯曲和偏心拉伸载荷下进行了测试。测试参数包括钢纤维含量（0%、1%、2%和3%）和偏心比（0、0.1、0.2、0.4、0.8和∞）。结果发现，所有试件均因裂纹局部化而失效。随着偏心比和钢纤维含量的增加，开裂、峰值和极限载荷时的应力和应变增加。对于钢纤维含量较高的试样，偏心比对裂纹和峰值强度的影响更为明显。对于常用纤维含量为 2% 的样品，随着偏心率从 0.1 升至 0.8，开裂强度和峰值强度分别增加 29% 和 63%。借助数字图像相关技术对样品表面进行全场测量，讨论了拉伸和弯曲复合载荷下 UHPC 的纤维桥接机理。然后，通过引入取决于偏心比和钢纤维含量的塑性影响系数，提出了确定开裂载荷的计算方法。最后，导出了一种预测UHPC在拉伸和弯曲联合作用下耦合强度的统一方法，并通过从现有文献收集的数据库验证了其稳健的适用性。