Abstract:This study presents the shear capacity of eco-friendly high-strength concrete (HSC) beams reinforced by 0.75% (by volume) of hooked steel fibers or shear stirrups with various spacings. Five large-scale HSC beams with steel fibers or stirrups were tested and investigated with respect to shear capacity, failure mode, and crack patterns. The test results indicate that all five tested beams finally failed by a shear-critical failure mode and that the use of 0.75 vol% of steel fibers significantly improved the she… Show more
“…[ 42 ] introduced the fibre efficiency factor, , that corrects the configuration of fibre. This is because hooked fibres transfer more load in the localized area of the hook than a straight deformed fibre and become more effective than having stirrups in the beam [ 43 ]. This factor is taken to be 1.0 for the hooked end, 0.75 for deformed, and 0.5 for smooth fibre.…”
“…[ 42 ] introduced the fibre efficiency factor, , that corrects the configuration of fibre. This is because hooked fibres transfer more load in the localized area of the hook than a straight deformed fibre and become more effective than having stirrups in the beam [ 43 ]. This factor is taken to be 1.0 for the hooked end, 0.75 for deformed, and 0.5 for smooth fibre.…”
“…Yuan et al [ 15 ]; presented an experimental study on the shear capacity contribution of steel fiber on the shear strength of HSC beams with and without stirrups. Five large-scale HSC beams with a steel fiber content of 0.75% by volume were tested.…”
One of the methods to improve the structural design of concrete is by updating the factors given in standard codes, especially when non-conventional materials are used in concrete beams. Accordingly, this study focuses on the colorations between the compressive strength and shear strength of high-strength concrete beams with and without steel fibers. For that purpose, different models are proposed to predict shear strength of high-strength concrete beams, by taking different combinations of the main variables: beam cross-section dimension (width and effective depth), reinforcement index, concrete compressive strength, shear span ratio, and steel fiber properties (volumetric content, fiber aspect ratio, and type of steel fibers). Multi-linear and non-linear regression analyses are used with large database experimental results found in the literature. The predicted results from the proposed equations are composed with different available models from codes, standards, and literatures. The calculated results showed better correlations and were close enough to the experimental data. Based on the data given in the standard codes, the shear strength is proportional to compressive strength (fc′) of the power 0.5. However, this value may not be adequate for modern cement and concrete containing steel fibers. Therefore, the mentioned power value must be reduced 5 times to 0.1.
“…In the cases of the P beams, since the elastic modulus of concrete was E c = 60 GPa from the material tests, the beams were under-reinforced, and they may reach the ultimate state with flexural tension failure. In this study, no stirrups were placed along the beams because P and H beams may be expected to enhance the shear resistance due to the bridging effect of the distributed steel fibers (JSCE 2004; Yuan et al, 2020). Figure 1.Dimensions of specimens and rebar arrangement.…”
Ultrahigh-performance fiber-reinforced concrete (UHPFRC) is an advanced cement-based composite material. Its ultrahigh compressive strength and high ductility can enable the downsizing of structural members, with special application to high-rise buildings. These excellent mechanical properties also allow its application in protective structures to resist high-speed penetration, low-velocity impact, and blast loading. UHPFRC with a compressive strength of approximately 150–200 MPa has traditionally been used to investigate the impact resistance of structural members under low-velocity impact loading. Recently, however, porosity-free concrete of the 400 MPa class of compressive strength has been developed. In this paper, to investigate the effects of the concrete strength and the steel fiber volume fraction on the impact resistance of porosity-free fiber-reinforced concrete (PFFRC) members, static and drop-weight impact loading tests were conducted on PFFRC beams by varying the volume fraction of steel fiber from 1 to 3.5%. As reference beams, 90 MPa high-strength fiber-reinforced concrete (HSFRC) beams with a 2% fiber volume fraction and normal-strength concrete (NSC) beams without stirrups and steel fibers were also tested. The results obtained from this study were as follows: (1) the static load-carrying capacity of a PFFRC beam can be enhanced by more than two and three times that of an NSC beam by adding 1 and 3.5% volume fractions of steel fiber, respectively; (2) a PFFRC beam with 3.5% fiber had the greatest impact resistance of all the beams considered in this study, and the beam with 2% fiber volume had the second-greatest performance, but the difference was small; (3) even though an HSFRC beam with 2% fiber had a smaller static load-carrying capacity than a PFFRC beam with 1% fiber, the former exhibited a slightly greater impact resistance than the latter because the bridging effect of the steel fibers has a greater influence under impact loading than under static loading.
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