Steel Fiber Ratio Research Articles

Hybrid fiber reinforced ultra-high performance coal gangue geopolymer concrete (UHPGC): Mechanical properties, enhancement mechanism, carbon emission and economic analysis

The low carbonization of ultra-high performance concrete (UHPC) has become a hot topic for sustainable development in the construction industry. Calcined coal gangue was used as aggregate and binder to prepare ultra-high performance coal gangue geopolymer concrete (UHPGC) in this paper. The hybrid reinforcement effect of steel fibers, calcium carbonate whiskers (CW), and carbon nanotubes (CNTs) on UHPGC was studied in the experiment. The results indicated that when the mixing ratio of straight steel fibers and hooked-end steel fibers was 2:1, the 28 d-compressive strength of UHPGC reached 145.94 MPa. However, excessive hooked-end steel fibers deteriorated the reinforcement effect of adjacent fibers and reduced the mechanical properties of UHPGC. CW and CNTs had a more significant improvement in the flexural properties of UHPGC. The bridging effect of CNTs and CW dispersed the stress on the matrix and delayed the formation and development of micro-nano cracks. Meanwhile, CNTs and CW improved the fiber bridging energy dissipation, thereby improving the flexural properties of UHPGC. The UHPGC had the highest flexural strength and flexural deflection of 13.59 MPa and 4.12 mm, respectively. The UHPGC prepared in this paper had lower carbon emissions and economic costs compared to traditional UHPC. Overall, this study provided valuable references for the resource utilization of coal gangue and the multi-scale strengthening and toughening of UHPGC.

Experimental behaviour and design model of FRP-UHPC-steel tubular columns under monotonic axial compression

By integrating structural steel with Fiber-Reinforced Polymer (FRP) and Ultra-High Performance Concrete (UHPC), FRP-UHPC-steel tubular columns (FUSTs) emerge as innovative composite members that offer exceptional corrosion resistance and lightweight properties. FUSTs hold significant potential for use as thin-walled tubular columns working in harsh environments, such as wind turbines and high-voltage transmission towers. To obtain in-depth understanding of key parameters including the steel fiber ratio of UHPC, the specimen void ratio and the FRP thickness, this paper tested 24 specimens to evaluate their compressive behaviour, including 18 FUSTs and 6 UHPC-filled FRP tubes (UCFFTs). Experimental results showed that: (1) FUSTs demonstrated ductile behavior with significant strain enhancement and notable strength improvement; (2) the steel fibers in UHPC had marginal influences on the ultimate condition of FUSTs; (3) a larger inner void had a general effect to lead to more localized rupture for the FRP tube; (4) the FRP thickness was the predominant influencing factor on both the general shape and the ultimate point of the normalized axial stress–strain curves. Finally, a design model was proposed, which was able to capture the general shape of the axial load–strain curves, and could generate reasonably accurate predictions for the peak load.

An Experimental Study on Compressive Properties of Composite Fiber Geopolymer Concrete

Background: The production process of Portland cement (OPC) consumes energy and releases carbon dioxide, which affects the environment. It has been found that geopolymer cementing material is a better substitute for it. The strength effect of fiber on geopolymer materials is the basis of the application of fiber geopolymer concrete in structural beams, slabs, and other components. Methods: Geopolymer concrete was prepared with fly ash, slag, and water glass as the main raw materials, and the effects of fiber type, quality, and blending method on the compressive properties and elastic modulus of geopolymer concrete were compared to explore the working mechanism of fiber-reinforced geopolymer concrete. Results: Through experimental research, the results showed that in 0.2% flocculent lignin fibers, when the mass ratio of carbon fibers was increased, the strength of the geopolymer concrete decreased. Due to the increased mass ratio of wavy steel fibers, comprising 0.2% flocculent lignin fibers, the strength enhancement effect was not apparent. Moreover, with regard to enhancing the modulus of elasticity of geopolymer concrete, blending fibers exerted the most significant effect. The fiber was added to geopolymer concrete to form a three-dimensional supporting frame system. When cracks occurred under the action of force, the development of cracks was limited due to the fibers, and the bonding slip delayed the propagation of cracks. The composite fiber could make full use of the advantages of each material and improve the strength of geopolymer concrete. Conclusion: The compressive properties of geopolymer concrete could be enhanced by blending single-fiber or mix-fibers, and the effect of mix-fibers was more optimal than that of others. The above research results provide a theoretical reference for the design of geopolymer concrete and a theoretical basis for the application of fiber geopolymer concrete in structural beams, slabs, and other components.

Investigation of notch position and fiber ratio on the fracture mode and energy of sfrc beam under the impact load

When the literature is examined, it is seen that a lot of study has been done on the crack propagation and fracture modes that occur under the influence of static loads in reinforced concrete (RC) structures. Studies in the literature show the effect of crack initiation, concrete compressive strength, and fiber volume fraction on the tension mode (Mode-I), shear mode (Mode-II), and mixed fracture mode that occurs in crack propagation under static load. However, the literature has not found a comprehensive study in which the fracture modes are examined under the effect of dynamic impact loading. For this reason, an experimental study has been planned in which hybrid steel fiber reinforced concrete (SFRC) notched beams with varying compressive strength will be tested under impact loading with a free-fall drop weight device designed by the authors. The experimental variables studied were determined as the change of the crack initiation point in the beams, the compressive strength of the concrete used to produce the beams, and the fiber volume fraction in the concrete mixture. The acceleration and impact load-time histories under the constant-energy-level impact loading applied to the beams were measured. Also, the crack shape, fracture mode, crack angle, and energy absorption capacities of the beams under impact load were interpreted. While the transition from Mode-I fracture form to Mode-II fracture form occurs under impact loading, the effects of concrete compressive strength and steel fiber ratio variables on energy absorption capacity, crack angle, and crack shape are studied. Increasing the distance of the notch from the beam midpoint in notched beams produced with concrete without fiber from 0 to 40, 80 and 120 mm caused the energy absorption capacity values to increase by an average of 39 %, 66 % and 86 %, respectively. Increasing the distance of the notch to the beam midpoint from 0 to 40, 80 and 120 mm in beams with 0.75 % and 1.5 % fiber ratio increased the energy absorption capacity values by an average of 40 %, 65 % and 86 %, respectively. In beams with 2.25 % fiber ratio, increasing the notch distance from 0 to 40, 80 and 120 mm increased the energy absorption capacity values by an average of 38 %, 62 % and 83 %, respectively.

Optimal Ratio of Steel and Polyester Fibers on the Mechanical Behavior of Alkali-Activated Concrete Produced by Industrial Waste Minerals

Optimal Ratio of Steel and Polyester Fibers on the Mechanical Behavior of Alkali-Activated Concrete Produced by Industrial Waste Minerals

The investigation and estimation of flexural strength in shear-critically designed RC beams considering the steel fiber content

Despite numerous studies investigating the effectiveness of steel fibers in RC members subjected to various loading conditions, the majority ignored the impact of the interaction between the tensile reinforcement ratio, compressive strength of fibrous concrete, and steel fiber dosage. This paper aimed to inspect and quantify the effects of hooked-end steel fiber dosage on the bending behavior of RC beams considering the interaction arising from various longitudinal reinforcement ratios. For this purpose, an extensive and hybrid investigation involving both experimental and numerical techniques was conducted. In the experimental part, an investigation was carried out to evaluate the contribution of a specific amount of fiber ratio and various aspect ratios to the behavior of large-scale RC beams having a shear-deficient design. Three beams with a 0.5% hooked-end steel fiber ratio and one without fibers but with a minimum amount of stirrups were produced, and three-point bending tests were conducted. All beams having fibers utilized full flexural strength as in the beam with stirrups. Once the experimental studies were completed, the numerical models were then developed and validated with those of experimental three-point bending tests using the non-linear finite element code VecTor2 to establish a basis for the comprehensive parametric study. The parametric study consisted of 33 analyses. Rebar and volumetric fiber ratios were selected to be variables, and the ratios adopted were within the typical range used in structural engineering applications. Based on the regression analysis a linear and a quadratic model were proposed for estimating the yield and peak strength depending on the steel fiber content. Finally, the obtained models were verified using work from the literature and found to be effective in forecasting the strength of shear-deficient RC beams with 0.8%, 1.0%, and 1.2% tensile reinforcement ratios and hooked end steel fibers (0.5 to 1.5%).

Experimental study on the strength properties of concrete modified with silica fume and steel fiber

Concrete is a widely used building material. It has excellent compressive strength but is brittle and relatively weak in tension. This experimental study aims to develop ductile and high-strength concrete by incorporating silica fume and steel fibers. Two types of steel fibers with aspect ratios of 52 and 72 were employed at varying percentages (0.44%, 0.88%, and 1.76% by mass of cement content). Additionally, 8.5% silica fume by cement mass was added to the concrete mixture. A water-to-cement (W/C) ratio of 0.42 and a slump of 100 mm are maintained. Substituting cement with silica fume improves the concrete's mechanical properties and elastic modulus. Moreover, adding steel fibers enhanced flexural and tensile strength. Increasing the percentage of silica fume and steel fibers correlated with higher compressive strength, while the aspect ratio of steel fibers has an inverse effect on compressive strength, with lower aspect ratios exhibiting a higher compressive strength. Furthermore, as the percentage of silica fume and steel fibers increases, the splitting tensile and flexural strength also improve, with the aspect ratio directly influencing these strengths, higher aspect ratios resulting in superior tensile and flexural strength. Ultimately, this investigation demonstrates that the strength properties of concrete rely on the content of silica fume, steel fibers, and the aspect ratio of the steel fibers.

Effects of steel fiber type and ratio on the one-way bending behavior of hybrid fiber reinforced concrete thin panels

Performance of hybrid fiber reinforced concrete (HyFRC) determined through standardized material tests usually correlates well with the structural performance. However, for thin panels, this correlation may be disturbed due to the fiber orientation and small crack surfaces, and more detailed investigations are required. In this study, effects of steel fiber type and ratio on the one-way bending behavior of HyFRC thin panels was investigated through concrete mixes obtained by using three different steel fiber types and polyvinyl alcohol (PVA) fibers. 45 dog bone shaped, notched specimens were cast and tested under direct tension to investigate the direct tension behavior of used HyFRC. Nine panels of 2500 × 500 × 50 mm in dimension were tested under three-point bending, and nine panels of 1240 × 500 × 50 mm in dimension were tested under four-point bending. An inverse analysis to obtain crack width-stress variation in three- and four-point bending specimens was also performed and behavior of steel fiber reinforced concrete specimens with and without PVA addition were compared. It was found that steel fiber type and ratio was consistently the dominant factor for all types of tests on HyFRC specimens. Addition of PVA fibers in HyFRC specimens either resulted in a similar or worse behavior for direct tension and three-point bending compared to their steel fiber only counterparts. Adverse effect of PVA fibers was more pronounced in three-point bending tests. On the other hand, PVA addition had a more positive effect in four-point bending tests. Inverse analyses performed on three-point bending tests revealed that stress levels develop between crack surfaces in these thin panels were significantly lower compared to direct tension stress levels. However, under four-point bending, these tensile stresses were closer to direct tension stresses, especially for specimens with shorter steel fibers. Loading conditions were found to be an effective factor in the behavior of HyFRC thin panels.

Tests and finite element modeling of concrete beams reinforced with reused steel bars

AbstractThis paper presents the experimental study and finite element modeling of the flexural behavior of concrete beams reinforced with reused steel bars as longitudinal reinforcements. The experimental program and results of eight reinforced concrete (RC) beams constructed with and without reused steel bars are described in detail. The replacement percentages of brand‐new bars with reused steel bars in the tested beams were 50% and 100%. The reused steel bars were coated with and without epoxy. Steel fibers with fractions of 0.5% and 1.0% of the concrete volume were added to the concrete mixes. The load‐deflection relationship, ductility index, toughness, and failure modes of the tested beams are presented and discussed. It is shown that utilizing reused steel bars decreases the ultimate load of RC beams but increases their deflection at the ultimate load compared with the control beam. Increasing the steel fiber ratio increases the ultimate load and the deflection at the ultimate load of RC beams incorporating reused steel bars. However, the zinc‐rich epoxy used to coat the reused steel bars does not affect the behavior of the beams. Three‐dimensional nonlinear finite element (FE) models of the tested beams were developed using ABAQUS and validated against the test results. The developed FE models are capable of accurately simulating the experimentally observed behavior of RC beams with reused steel bars.

Experiment on Concrete by Adding Steel Fibers and Plastic Waste to Reduce Environmental Issues and Adding Strength to Concrete

Abstract: Concrete is the most commonly used material for construction in civil engineering. The project involves the proposed concrete which is made up of adding plastic in concrete may help to reuse the plastic as one of the constituent material of concrete. Due to rapid industrialization the amount of use and decomposition of plastic has increased. If we are able to utilize this waste under proper conditions as addition to concrete it will reduce the plastic waste up to some extent. By adding the steel fibers to the above mix it will increase the compressive strength of the concrete. M40 grade concrete is used in the whole procedure. Here, we used 4 different percentages of plastic waste (i.e., 0.6%, 1.2%, 1.8%, and 2.4%) of weight of cement and by taking quantity of steel fiber as constant (i.e., 2%) of weight of cement, and the aspect ratio of steel fibers is 60. The concrete cube of size 150mm×150mm ×150mm are prepared and tested at 3days, 7days, 14days and 28 days. The resulting data has been analyzed and compared with controlled specimens.

Sustainable one-part alkali activated slag/fly ash Geo-SIFCOM containing recycled sands: Mechanical, flexural, durability and microstructural properties

Slurry Infiltrated Fiber Concrete or Composite (SIFCOM) is a unique form of steel-fiber-reinforced cement composite that possesses exceptional toughness and superior mechanical properties like compressive, shear, tensile, and flexural strengths. New supplies of fine aggregate are required since the construction industry is experiencing natural sand shortage. By thoroughly evaluating workability, mechanical properties, flexural toughness, durability and microstructure, this study demonstrates the potential of various recycled sands from different sources in the manufacture of sustainable slag/fly ash one-part alkali activated SIFCOM (Geo-SIFCOM). Recycled concrete, brick and ceramic sands were used as a substitute of 10, 25 and 50% by volume of silica sand. Steel fiber ratios of 5%, 10%, and 15% were used and exposed to heat curing for 6, 24 and 48 h at 80 °C. Taguchi method was used to investigate the optimum mixture. The results showed that 24 h heat-cured mixture containing 25% recycled concrete sand and 15% fiber (C25F15) had the largest compressive strengths of 68.49 MPa, 74.53 MPa and 80 MPa at 7, 28, and 91 days, respectively. All 6 h – cured mixtures containing 100% slag exhibited the best resistance to freeze-thaw and the mixtures heat cured for 6 h demonstrated the best compressive strength resistance to elevated temperature and F-T cycles regardless of FA content. The largest flexural toughness was also assessed for the mixture with 50% brick sand and 15% fiber (B50F15) heat-cured for 6 h. The mixture with 50% FA and 50%slag (50% ceramic sand and 15% fiber) exhibited the best high temperature resistance.

Shear capacity of reinforced concrete beams with recycled steel fibers

Abstract This study investigates the effect of using recycled steel fibers (RSFs) extracted from cut tires with dimensions of 0.8 and 40 mm in diameter and length, respectively. Different percentages of fibers were used, which are 0.5, 1, 1.5, and 2%. Ten beams with dimensions of 150 mm × 240 mm and a length of 1,700 mm were tested, two of which are control beams without stirrups and using stirrups at a distance higher than the upper limit (d/2), which is a distance of 250 mm. In the case of using steel fibers without a stirrup, it is noticed that shear resistance increases gradually, but the type of failure remains shear. When using a minimum stirrup with steel fibers, the shear resistance increased significantly by 11.1, 23.7, 33.3, and 41.4%, respectively, compared to the reference beam without steel fibers so that the increased shear capacity in the presence of the minimum stirrups and optimal ratio of steel fibers of 2% reaches 122%, compared to the reference beam without stirrup and steel fibers, as well as converting the type of failure from shear failure to pure bending failure. When using a stirrup, this effect will be greater. The presence of RSF reduces deflection at cracking load, while increasing deflection at the ultimate load. Therefore, the stiffness and ductility ratio increased with the presence of steel fibers by 41.5 and 50.3%, respectively. Also, steel fibers delayed the appearance of beam cracks and reduced their widths.

Comparative study on the effect of steel and plastic synthetic fibers on the dynamic compression properties and microstructure of ultra-high-performance concrete (UHPC)

Ultra-high-performance concrete (UHPC) shows great potential in constructing concrete structures subjected to impact and explosive forces. In order to make UHPC structures more ductile and cost-effective, this study used four-volume fractions of plastic synthetic fiber (PSF) instead of conventional steel fibers (SF) to prepare ultra-high-performance hybrid fiber-reinforced concrete (UHP–HFRC) with a total fiber weight of 2%. The dynamic compression properties at four strain rates were also investigated using a split Hopkinson pressure bar (SHPB) test. The results show that the addition of PSF reduces the flowability and compressive strength of UHPC but contributes significantly to the flexural strength of UHPC. UHP-HFRC demonstrates higher integrity under impact loading and significant sensitivity to strain rates. As the strain rate increases, both the dynamic compressive strength and dynamic growth factor of UHP-HFRC increase, with the optimal mixing ratio of PSF and SF being 1:3.Combined with the SEM and nanoindentation test results, it can be found that the bonding ability of PSF to the substrate is stronger, and the interface zone between PSF and the substrate is 10um smaller than that between sf and the substrate. It can be concluded that it is difficult for PSF to fully replace steel fiber in referencing UHPC, while hybrid fibers should be a good choice to produce excellent UHPC composite.

Statistical Investigation of the Effects of w/c, Cement Dosage and Fibers on Bond Strength and Carbonation Coefficient of Hybrid Fiber Concretes

Fiber reinforced concretes are preferred due to high tensile strength in structural elements. Alongside to tensile strength, supplying good adherence with concrete and its durability against time are also expected properties. A four-factor experimental test program was created in this study to investigate the effect of fiber type and quantity on the strength and durability performance of hybrid fiber concretes (FRC). In addition to steel fiber ratio (STF) and glass fiber ratio (GF), basic criteria of concrete such as water/cement ratio and cement dosage were chosen as independent variables. Flexural and compressive strength, bond strength, stripping time of steel reinforcement and 180, 270 and 360-day carbonation depths of FRC were investigated experimentally. The Carbonation coefficients of each FRC were calculated and a correlation was obtained for a general “Ke” carbonation coefficient by Multi Linear Regression. Average of K was 0.219 mm√days. Stripping time of steel reinforcement from FRC was two times longer in samples containing only STF than samples containing only GF. With the dual combination of STF and GF, this time has been increased approximately 4 times.

Effect of Contents, Tensile Strengths and Aspect Ratios of Hooked-End Steel Fibers (SFs) on Compressive and Flexural Performance of Normal Strength Concrete

This study is a part of the study to simplify the reinforcing details of reinforced concrete (RC) structural members by substituting the conventional reinforcement with hooked-end steel fibers (SFs). This paper investigates the effects of SF strength, dosage and aspect (l/d) ratio on the compressive and flexural behaviors of normal strength concrete with specified compressive strength of 30 MPa. In this study, hooked-end SFs of high strength (2000–2400 MPa) and normal strength (1100–1200 MPa) were used with three l/d ratios of 64, 67 and 80. Hooked-end SFs were incorporated with three dosages of 20 kg/m3 (0.25 vol.%), 40 kg/m3 (0.50 vol.%) and 60 kg/m3 (0.75 vol.%). Eighteen steel fiber reinforced concrete (SFRC) mixes were mixed. To evaluate the compressive and flexural performance of each SFRC mixture, three SFRC cylindrical and prismatic specimens for each mixture were manufactured and tested, respectively. The test results that the inclusion of hooked-end SFs had little effect on the compressive strength, while it improved the toughness of concrete. Hooked-end SFs were also found to be effective in enhancing the flexural performance of concrete. The dosage and properties (strength and l/d ratio) of SFs significantly affect the residual flexural tensile strength (fR1 and fR3) at serviceability (SLS) and ultimate limit state (ULS) defined in fib Model Code 2010 (MC2010).

Compressive behavior of steel-polyethylene hybrid fiber reinforced cementitious composite

A hybrid fiber reinforced cementitious composite (HFRCC) was produced by mixing steel fiber (SF) and polyethylene fiber (PE) together in the cement matrix with an appropriate ratio. Under the same PE volume percentage, the effect of various SF aspect ratios (30, 50, 65, 83.3, and 108.3) and volume percentages (0%, 0.3%, 0.6%, and 0.9%) on the compressive behavior of HFRCC was experimentally studied. The results indicated that the aspect ratio and volume percentage of SF had little effect on the elastic modulus of HFRCC. With the addition of SF, the maximum increase of compressive strength and peak strain reached 33.82% and 24.29%, respectively. And the HFRCC presented maximum compressive strength and peak strain when the aspect ratio of SF was 108.3 and the volume percentage was 0.6%. In order to reveal the compressive constitutive relationship of HFRCC, a piecewise function was adopted based on the comparison of existing theory and furthermore in which the fiber reinforcing index, compressive strength, peak strain, and elastic modulus had been introduced. It is concluded that the proposed compressive constitutive model has more agreement with test data.

Structural Behavior of Reactive Powder Concrete under Harmonic Loading

Industrial buildings usually are designed to sustain several types of load systems, such as dead, live, and dynamic loads (especially the harmonic load produced by rotary motors). In general, these buildings require high-strength structural elements to carry the applied loads. Moreover, Reactive Powder Concrete (RPC) has been used for this purpose because of its excellent mechanical strength and endurance. Therefore, this study provides an experimental analysis of the structural behaviors of reinforced RPC beams under harmonic loads. The experimental program consisted of testing six simply supported RPC beams with lengths of 1500 mm, widths of 150 mm, and thicknesses of 200 mm under harmonic loading with varied frequencies between 10 and 20 Hz. Different steel fiber ratios of 0%, 0.5%, 0.75%, 1.0%, 1.5%, and 1.75% were provided in the concrete mixes to explore the effect of steel fibers on the dynamic behavior of these beams. Except for the steel fiber volume fraction, all of the examined specimens shared the same material attributes and reinforcing details. The outcomes proved the positive effect of adding steel fibers on the dynamic response under the effect of harmonic loading. The optimum volume fraction of steel fibers was characterized by a percentage of 1.5%. Moreover, the vibration amplitude was more affected by the steel fibers than the support reactions. The inertial force increased as the harmonic loading duration increased. This increase in the inertial force by the load duration was enhanced after adding the steel fibers. However, this enhancement started to decline after increasing the steel fiber content to 1.75%.

A case study of T-beams with hybrid section shear characteristics of reactive powder concrete

Abstract As an extension of recent developments in concrete understanding, an extensive study is currently being conducted on the structural performance of reactive powder concrete (RPC). This article guides how to investigate the shear behavior of RPC T-beams and calculate their ultimate and breaking shear capacities. The mechanical features of this construction material and approach to revising the reactive powder shear hybrid segment T-beams are cast-off in this motion and are investigated in this experimental study. To evaluate the effects of volumetric ratio of steel fibers, silica fume ratio, and tensile steel ratio, introductory section on the effectiveness of T-beam shearing reactive powder, the program of experimentation involved trying four beams. The research aimed to determine the deflection conduct of the load, downtime approach, strain amount over the beams’ depth, and failure form of cracks. In examining reaction powder’s mechanical characteristics mixtures, steel fiber volumetric ratio and silica fume volumetric ratio were also studied. Furthermore, a hybrid beam study revealed that by using reactive powder web and regular concrete in flange effectively, T-beam concert is enhanced when associated with normal concrete T-beams by 12%. Hybrid beams have also revealed that using reactive powder flange and usual concrete in a web effectively advances the show of T-beams when associated with standard concrete T-beams by 28%.

Cracking Pattern and Bearing Capacity of Steel Fiber-Reinforced Concrete Single-Layer Tunnel Lining

In recent years, steel fiber-reinforced concrete (SFRC) single-layer linings have been used in tunnel engineering. Compared to plain concrete single-layer linings, SFRC single-layer linings demonstrate enhanced bearing capacity, durability, and sustainability. Existing studies primarily focused on the mechanical properties of SFRC; however, limited investigations have been conducted on the cracking pattern of SFRC linings. This study uses laboratory tests to examine the influence of steel fiber content and aspect ratio on the mechanical properties of concrete, such as compressive strength and elastic modulus. After the recommended content and aspect ratio of steel fiber are proposed through tests, the cracking pattern and safety performance of plain concrete and SFRC linings under surrounding rock pressure are studied using a similar model test. The test results indicate that the recommended steel fiber volume fraction and aspect ratio for CF35 SFRC are 0.58% and 70, respectively. Due to the effect of loose load, cracks initially develop on the inside of arch crowns in both plain concrete and SFRC single-layer linings. Subsequently, new cracks appear on the inside of the lining floor and the outside of the two wall feet. Numerous narrow cracks with rugged and winding expansion paths can be found on SFRC single-layer linings. Conversely, plain concrete single-layer linings exhibit fewer cracks with larger widths along a straighter path. The initial cracking load of a single-layer lining made of plain concrete is 0.027 MPa, whereas for a single-layer lining made of SFRC, it is 0.04 MPa. This indicates that SFRC can effectively enhance the initial cracking load of lining structures. In the event of damage to the lining, the most critical area for the plain concrete single-layer lining is at the two wall feet, where the minimum safety factor is 1.66. However, for the SFRC lining in the same location, the safety factor is 2.7, resulting in a 62.7% increase in safety.

The Shear Capacity Estimation of Reinforced Concrete Short Beams with Steel Fiber by Digital Image Correlation Approach

This research aimed to estimate the shear capacity of reinforced concrete short beams with steel fiber (RSF short beams) using DIC (digital image correlation). Four-point bending tests of RSF short beams with shear span ratio (a/d) of 1.0, 1.5, and 2.0 were conducted. 0.5% or 1.0% volume fraction of steel fiber was used. The distribution of minimum principal strain (Ɛ2) was obtained from DIC then the width of compressive strut was evaluated. The effects of volume fraction of steel fiber and shear span ratio were investigated. Finally, the shear capacity of RSF short beams was estimated with the help of DIC.