The rate-sensitive properties of ultra-high performance concrete (UHPC) subjected to flexural and direct tensile loads were investigated. Dynamic flexural tests were performed by means of a drop hammer impact machine, whereas a servo-hydraulic system was utilized to conduct direct tension tests. The absorbed energy of the UHPC specimens under flexure increased from 0.74 to 4.49 J as the input energy varied from 6.7 to 67 J. The load-bearing capacity and maximum flexural deformation exhibited identical trends as the input energy increased. The high-speed tensile properties, including strength, ductility, and energy dissipation capacity, improved upon increasing the strain rate up to 100 s^-1. A nonuniform distribution of the deformation of UHPC specimens under high-speed tension was observed by identifying the zones of strain localization (near crack), uniform strain (far field), and shear lag (transition zone in between) using digital image correlation. The full-field data of displacement, strain, and strain rates were obtained and quantitatively evaluated. The results indicated that multiple mechanisms were involved in the rate-dependent behavior of the UHPC specimens.

研究了超高性能混凝土（UHPC）在弯曲和直接拉伸载荷下的速率敏感性。动态弯曲试验是通过落锤冲击机进行的，而伺服液压系统用于进行直接的张力试验。当输入能量从6.7变化到67 J时，UHPC试样在弯曲状态下的吸收能从0.74增加到4.49J。随着输入能量的增加，承载能力和最大挠曲变形呈现出相同的趋势。将应变率提高到100 s ^-1可以改善包括强度，延展性和能量耗散能力在内的高速拉伸性能。通过使用数字图像相关性识别应变局部化区域（近裂纹），均匀应变（远场）和剪切滞后区域（它们之间的过渡区域），观察到高速拉伸下UHPC试样的变形不均匀分布。获得了位移，应变和应变率的全场数据，并进行了定量评估。结果表明，多种机制参与了UHPC标本的速率依赖性行为。