Dynamic fracture toughness of ultra‐high‐performance fiber‐reinforced concrete under impact tensile loading

Abstract

The fracture toughness and fracture energy of ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) at both static and impact rates (43–92 s−1) were investigated using double‐edge‐notched tensile specimens. Two types of steel fiber, smooth and twisted fiber, were used in producing UHPFRC with different volume ratios of 0.5%, 1.0%, 1.5%, and 2%. The results indicated that UHPFRCs produced very high fracture resistance at impact rates, with first stress intensity factor (KIC) up to 3.995 MPa√m, critical stress intensity factor (KIC*) up to 7.778 MPa√m, and fracture energy (GF) up to 86.867 KJ/m2, which were 2.5, 5.0, and 16.9 times higher than those of ultra‐high‐performance concrete, respectively. The KIC* was clearly sensitive to the applied loading rate, whereas the KIC and GF were not. Smooth fiber specimens exhibited not only higher KIC* and GF at impact rates but also higher dynamic increase factor than twisted fiber specimens. A minimum fiber volume content of 1% should be used in UHPFRC to provide a significant enhancement in crack resistance. The maximum value of UHPFRC crack velocity at impact rates was found to be 527 m/s by using a dynamic fracture mechanic model.

Strain rate sensitivity of strain‐hardening fiber‐reinforced concrete subjected to dynamic direct tensile loading

“…Since the energy release of the impact machine strongly depends on the capacity of the notch coupler, a small error in the production of the notch depth can result in a considerable difference in the energy release and the strain rates of the specimens. 1 For this reason, within the same series, three specimens were produced with different strain rates. For example, in series M1HD, the generated strain rates for three specimens were 9, 17, and 15 s À1 , while in series M1TD, they were 8, 13, and 17 s À1 .…”

“…Strain-hardening fiber-reinforced concretes (SHFRCs) including high-performance fiber-reinforced concrete (HPFRC) and ultra-high-performance fiber-reinforced concrete (UHPFRC) have been demonstrated to exhibit superior tensile resistance with high tensile strength, ductility, and energy absorption capacity even under high strain rate loading owing to their unique strain hardening behavior. [1][2][3][4][5][6][7][8] These superior properties make SHFRCs promising for various structures including bridges, gas tanks, offshore structures, nuclear reactor containment shields, heavy-duty runways, defense shelter, crash barriers, and more, which are exposed to extreme loading conditions such as earthquakes, impacts and blasts. 9 Currently, SHFRCs have been applied to real-life bridge structures such as the 33-m Mars Hill Road bridge in US, the 36.4-m-span Akakura Onsen Yukemuri Bridge in Japan, the 60-m single-span Sherbrooke pedestrian bridge in Canada, the Seonyu footbridge in South of Korea, the Saint Pierre La Cour bridge in France, Kampung-Linsum bridge in Malaysia, etc.…”

Assessment of fracture energy of strain‐hardening fiber‐reinforced cementitious composite using experiment and machine learning technique

“…7 Fracture energy is the most commonly used parameter to evaluate the energy absorption capacity of SHFRCC. 8 In addition, fracture energy is implemented in material models and it plays an important role in determining the numerical simulation accuracy of the nonlinear behavior of structures using SHFRCC. In order to measure the fracture energy of SHFRCC, several test methods including weld splitting tests, three-point bending tests, and direct tensile tests, have been proposed.…”

“…Fracture energy is the most commonly used parameter to evaluate the energy absorption capacity of SHFRCC 8 . In addition, fracture energy is implemented in material models and it plays an important role in determining the numerical simulation accuracy of the nonlinear behavior of structures using SHFRCC.…”

On the efficiency of induced prestressing in SMA mortar beams through different thermal stimuli

“…Over the past decades to now several efforts have been conducted for reinforcing cementitious structures using conventional steel fibers through different types of geometries (end-hooked, polygonal twisted, crimped, and so on) [1][2][3][4]. Although there may exist some basic diversities in terms of end-forms, methods of productions (continuous or discontinuous), and bond mechanism, all of them provide passive resistance activated with relatively large deformation [5][6][7][8].…”