Jang Eun-Yoo, Kim Jung J, Yoo Doo-Yeol
Department of Architectural Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea.
Department of Civil Engineering, Kyungnam University, 7 Kyungnamdaehak-ro, Masanhappo-gu, Changwon-si, Gyeongsangnam-do 51767, Korea.
Materials (Basel). 2019 Oct 15;12(20):3365. doi: 10.3390/ma12203365.
This study examined the influences of fiber geometry, inclination angle, and loading rate on the pullout behavior of multiple steel fibers in ultra-high-performance concrete (UHPC). For this, two different steel fiber types, i.e., straight (S-) and hooked (H-), four different inclination angles (0°-60°), and four different loading rates (0.018 mm/s to 1200 mm/s) were considered. Test results indicated that the pullout performance of S-fibers in UHPC was improved by increasing the loading rate. The highest maximum pullout load of the S-fiber was obtained at the inclination angle of 30° or 45°. The maximum pullout loads of H-fibers also increased with increases in the loading rate, while their slip capacities rather decreased. No specific inclination angle was identified in the case of H-fibers that caused the highest maximum pullout load. The H-fibers yielded higher average bond strengths than S-fibers, but similar or even smaller pullout energies under the impact loads. The aligned S-fiber in UHPC was most sensitive to the loading rate compared to the inclined S-fiber and aligned H-fiber. The rate sensitivity became moderate with the fiber inclination angle. Consequently, the aligned S-fiber was recommended to achieve the best energy absorption capacity and interfacial bond strength at various impact loads.
本研究考察了纤维几何形状、倾斜角度和加载速率对超高性能混凝土（UHPC）中多根钢纤维拔出行为的影响。为此，考虑了两种不同类型的钢纤维，即直形（S-）和带钩形（H-），四种不同的倾斜角度（0°至60°），以及四种不同的加载速率（0.018 mm/s至1200 mm/s）。试验结果表明，通过提高加载速率可改善UHPC中S纤维的拔出性能。S纤维在30°或45°倾斜角度下获得最高的最大拔出荷载。H纤维的最大拔出荷载也随加载速率的增加而增加，但其滑移能力反而降低。在H纤维的情况下，未发现导致最高最大拔出荷载的特定倾斜角度。H纤维的平均粘结强度高于S纤维，但在冲击荷载下的拔出能量相似甚至更小。与倾斜的S纤维和排列的H纤维相比，UHPC中排列的S纤维对加载速率最为敏感。随着纤维倾斜角度的增加，速率敏感性变得适中。因此，建议使用排列的S纤维，以在各种冲击荷载下实现最佳的能量吸收能力和界面粘结强度。
