Application Of Steel Fiber Reinforced Concrete Research Articles

Flexural behavior of SFRC-NC composite beams: An experimental and numerical analytical study

In this study, the flexural behavior of SFRC-NC composite beams cast with normal concrete (NC) and steel fiber-reinforced concrete (SFRC) were investigated. Nine SFRC-NC composite beams were designed and tested through four-point bending (FPB) experiments, including one reference beam with normal concrete (NC) and eight beams with different SFRC layer thicknesses. The effect of the designed parameters, including the SFRC layer thickness, diameter of steel rebar, and fiber content, on the flexural behavior of the beams was investigated experimentally. Compared to beams cast with normal concrete, the experimental results showed that the application of SFRC can effectively improve the bearing capacity of RC beams. These improvements include the crack-initial load, yield load, ultimate load, and ductility. Based on the experimental results, an FE macro-model was developed, and a series of numerical analyses were conducted to investigate the flexural behavior of SFRC-NC composite beams.

A Comprehensive Analysis of the Use of SFRC in Structures and Its Current State of Development in the Construction Industry.

In recent years, concrete technology has advanced, prompting engineers and researchers to adopt advanced materials to improve strength and durability. Steel-fiber-reinforced concrete (SFRC) represents the substantial modification of concrete materials to improve their structural properties, particularly their flexural and tensile strength. Whether SFRC is stronger than conventional concrete depends on a variety of variables, including the volume, size, percentage, shape, and distribution of fibers. This article provides a comprehensive discussion of the properties of SFRC, such as durability, fire resistance, and impact resistance or blast loading, as well as the application of SFRC in structural members including beams, columns, slabs, and walls. The application of steel fibers in various types of concrete, including pre-stressed, pre-cast, self-compacting, and geopolymer concrete, was also examined in this comparative analysis review, and recommendations for the future scope of SFRC were identified.

Application of steel fiber-reinforced concrete for slab lagging at underground mines in Quang Ninh

Steel Fiber-Reinforced Concrete (SFRC) is an advanced material studied and used in some developed countries in the world in recent years. The characteristics of this concrete are intensive compression, high tensile and tolerance strength, higher repeated loads, and long-term durable stability. Steel fibers were used to manufacture SFRC because of their outstanding characteristics. The durability of SFRC should be improved and the disadvantages of traditional concrete should be reduced. To produce inserts in the support structure, SFRC must be applied. Because 60÷70% of tunnels are being constructed for underground coal mines of Vietnam National Coal and Mineral Group (TKV) currently use. SPV steel frame support in combination with reinforced concrete inserts steel. To increase the plaque's capacity and durability in the future, a study must be done to create new, very intense concrete materials. This study investigated how the ratio and compressive strength of steel fibers affected the flexural characteristics of SRFC. To achieve this, 30 MPa strength SFRC with 0.5%, 1.0%, and 1.5% fiber fractions were made and evaluated. This study’s experimental results can be summarized as follows: according to the compression experimental results, the compressive strength and elastic modulus of SFRC were not considerably impacted by the steel fiber volume ratio; The experimental results from the bending tests show that for concrete with a strength of 30 MPa, the proportion of steel fibers of 1.0% has higher flexural strength and toughness than the proportion of steel fibers of 0.5% and 1.5%; A comparison of the test at 28 days of age with the (ACI 211.1-91, 1991) was completely satisfied.

Non-normal distribution of residual flexural strengths of steel fiber reinforced concretes and its impacts on design and conformity assessment

Variability of concrete properties has strong influences on design and conformity assessment. However, variability of residual flexural strengths of steel fiber-reinforced concrete (SFRC) has yet been statistically investigated. In this study, a large number of SFRC specimens was sampled from a central mix concrete plant manufacturing precast SFRC elements for a real civil infrastructure project. Variability of residual flexural strengths of SFRC are reported. Results show that the residual flexural strengths of SFRC follow the log-normal distribution at large crack month opening displacement (CMOD). The origin that leads to the log-normal distribution of the residual flexural strengths of SFRC is discussed. The use of an assumed normal distribution of the residual flexural strengths of SFRC in the current design approach and conformity assessment results in more than 30% overdesign and more stringent acceptance criteria. This leads to higher materials cost and higher producer's risk, which discourage the wider adoption and application of SFRC. The logarithmic transformation provides a practical and convenient approach to design and to check the conformity of log-normally distributed SFRC properties adopting existing criteria. Compared to the typical lab-based study with limited number of specimens and test results from a well-controlled environment for material processing and specimen preparation, the field study reflects more closely the true material variability in real construction. Thus, the statistical analysis obtained and conclusions drawn from the current work are more representative.

Experimental Investigation on Columns of Steel Fiber Reinforced Concrete with Recycled Aggregates under Large Eccentric Compression Load.

To improve the structural application of steel fiber-reinforced concrete with recycled aggregates (SFRC-RA) composited in gradation by large-particle natural coarse aggregate and small-particle recycled coarse aggregate, the large eccentric compression behavior of eight SFRC-RA columns was experimentally investigated in this paper. The main parameters considered were the strength of the SFRC-RA and the volume fraction of the steel fiber. Details about the sectional concrete strain, the longitudinal steel bar strain, the lateral displacement, the cracking load, the crack distribution and crack width, and the ultimate load of the SFRC-RA columns were measured. The beneficial effects of steel fiber on these attributes were discussed, and the ductility corresponding to the lateral displacement of the SFRC-RA columns was also analyzed. Based on the test results and design principles, formulas were proposed for predicting the cracking resistance, crack width, and lateral displacement of SFRC-RA columns in a normal service state. The ultimate loads of the SFRC-RA columns under a large eccentric compression load were calculated, considering the second-order effects.

Seismic behavior of 3-D ECC beam-column connections subjected to bidirectional bending and torsion

Special moment resisting frames (SMF) are commonly used in low- and medium-rise buildings located in regions of high seismicity. Although adequate performance of this seismic force resisting system was observed in prior earthquakes in terms of protecting buildings from collapse, the formation of plastic hinges in the beams and columns causes irreparable damage to the beam-column connections. Recently, interest in using fiber-reinforced concrete (FRC) has been growing to enhance energy absorption capacity and damage tolerance of beam-column connections and other components in reinforced concrete (RC) buildings. Prior research has mostly focused on the application of steel FRC (SFRC) in 2-D beam-column connections. However, little is known about the performance of exterior beam-column connections that are usually subjected to more complex loading during an earthquake, involving bi-directional bending and torsion of the column. In addition to the loading, the geometry of the connection requires a more involved test setup (i.e., with an out-of-plane beam and proper boundary conditions). In this research, the use of engineered cementitious composites (ECC) in 3-D exterior beam-column connections is investigated experimentally to improve building seismic performance. ECC is a special class of high-performance fiber-reinforced cementitious composites (HPFRCC) that, compared to conventional concrete, exhibits higher tensile ductility, energy absorption and shear resistance, in addition to improved bond performance with reinforcing steel (rebar). To understand the performance of exterior beam-column connections under complex loading conditions, scaled 3-D specimens were constructed and tested under simulated seismic loads. To improve the performance of the connections, conventional RC was replaced with reinforced ECC (RECC) that extends from the panel zone to the adjoining beams and columns to cover the potential plastic hinge regions. This paper discusses the loading protocols, the test setup for 3-D exterior beam-column connections, and the improvement in the joint behavior with the application of RECC as compared to conventional RC. The results suggest that the efficient use of ECC in the potential plastic hinge regions can improve the capacity and damage tolerance of beam-column connections under realistic seismic loading conditions.

Application of SFRC in steel–concrete composite beams subjected to hogging moment

This paper describes the effects of SFRC on improving the mechanical performance of composite steel and concrete beams subjected to hogging moment. Four specimens with different concrete slabs and different shear connectors were examined experimentally in this study. Steel fiber reinforced concrete (SFRC) was used for two specimens, and normal concrete was applied for the other two specimens. Different types of shear connectors, including shear studs and Perfo-Bond Strips (PBLs), were used on steel–slab interface of the specimens. Shrinkage of the normal and steel fiber reinforced concrete, load versus mid-span deflection relationship, crack formation and its propagation process, and slip development on the steel–slab interface were measured and investigated. The test results show that the inclusion of steel fibers decreased both the crack spacing and crack width of the concrete slab. The specimens with steel fiber reinforced concrete have relatively large initial cracking load, and crack width of the concrete slab can be controlled appropriately in the service stage. The effects of the SFRC on the ultimate load carrying capacity of the beam depend on the shear connectors applied on the steel–slab interface. The application of SFRC could enhance the load carrying capacity of the specimen with stud shear connectors, however, the effects of SFRC on the load carrying capacity of PBL specimen were found to be declined in some extent. Besides, the current specifications, such as AASHTO, EUROCODE-4 and JSCE, are typically conservative in predicting the ultimate load carrying capacity for composite beams under hogging moment.

Seismic Performance of SFRC Piers under Reversed Cyclic Loading

Steel fiber reinforced concrete (SFRC) has many good dynamic performances such as toughness and ductility. However, few studies have focused on SFRC’s application in bearing member of bridge structures. In this paper, pseudo-static cyclic tests of eight pier specimens are carried out to investigate seismic behavior of piers using SFRC. The main variables in the testing are the steel fiber content (volume fraction of 0.0%, 0.5%, 1.0% and 1.5%), the length of SFRC region and the stirrup ratio of piers. Seismic behavior of the test specimens, like the failure pattern, the hysteretic characteristics, the skeleton curves, the ductility and the energy dissipation are investigated experimentally. The results show that, 1) the SFRC pier with the steel fiber volume fraction of 1.0% has much better performance than that with other fiber volume contents, particularly for bearing capacity, hysteretic energy dissipation and ductility; 2) the pier specimen can keep sufficient seismic capacity, in which some stirrups are replaced by steel fibers; and 3) compared with specimen with application of SFRC in entire pier, the specimen with appropriate local application of SFRC in potential plastic hinge region can sustain almost the same seismic properties, such as the ultimate bearing capacity, the stiffness, the ductility and the energy dissipation capacity.