Rate effect on interfacial response between fibres and matrix

Spacing and bundling effects on rate-dependent pullout behavior of various steel fibers embedded in ultra-high-performance concrete

“…This is significantly higher than the increases of other multiple-fiber specimens, showing about 21-55% increases, and the single-fiber specimen. Pacios et al [26] reported that increasing the number of fibers from 8 to 16 with a decrease in the fiber spacing was effective in increasing the loading rate sensitivity but ineffective in changing the average bond strength, consistent with the findings of this study for the case of straight steel fiber.…”

“…The straight fiber spacings corresponding to volume fractions of 1%, 2%, and 7% resulted in DIFs of 1.21-1.45, 1.45-1.55, and 1.32-1.43, respectively. The occurrence of higher rate sensitivity in specimens with smaller fiber spacings is also reported in previous studies [26]. In addition, as the fiber spacing of multiple-fiber specimens decreased, the deviation between the maximum pullout loads of the fibers decreased [27].…”

Resilience of Cities to Terrorist and other Threats

“…Banthia and Trottier (1991) performed pull-out tests on aligned steel fibers at a COD rate of 1,500 mm/s and reported that the deformed steel fibers showed a greater sensitivity to rate than smooth fibers and produced smaller slips at higher rates of COD. This was in sharp contrast to the findings of Pacios et al (1995) who showed that for straight steel fibers in an aligned group, the slips under impact were higher than those under quasi-static conditions, and the overall 175 (2001a) demonstrated ( Figure 1) that very different flexural toughness…”

“…One major difference between the various studies cited above is how the inertial part of the applied load was dealt with. While a proper dynamic analysis was performed in Trottier, 1991), in (Gokoz andNaaman, 1981) and (Pacios et al, 1995), a rubber pad was introduced in the contact zone and inertial forces were ignored. As discussed above, it is now well recognized that inertial loading must be explicitly considered in all impact testing.…”

“…) Limited efforts have been made to model the bond-slip process as a function of the strain rate. From the traditional R-curve approach in fracture mechanics, Pacios et al (1995) assumed that the point of intersection of the R-and G-curves was a function of the slip-rate. That is (Figure 3), the ratio of the crack length at m to that at n depends upon the slip-rate as:…”