This study aims to evaluate the flexural behavior of I-shaped cross-sectional steel-fiber-reinforced concrete (SFRC) beams that are reinforced with prestressed glass fiber reinforced polymer (GFRP) ...and steel rebars (hybrid reinforcement, HR). The results obtained in the experimental tests on these SFRC beams are compared with those of reinforced concrete (RC) beams that include Z-shape stirrups. The geometry of the groups of beams is equal, but the reinforcement configurations are different. The HR system is formed by prestressed GFRP bars and prestressed steel strands, and seeks to achieve a balance between reinforcement effectiveness, durability, ductility, and cost-competitiveness. The GFRP bars have relatively low elasticity modulus, tensile brittle failure, and intense damage under high temperatures, but are not susceptible to corrosion. Pre-stressed steel strands, disposed with adequate concrete cover to decrease their probability to corrosion, have higher modulus of elasticity and ductile failure, guaranteeing the beam’s flexural capacity in case of a fire event. The results obtained on four-point monotonic loading tests are presented and discussed, including the load level at service and ultimate limit state conditions, deformability, and failure mode. The influence of hybrid and fiber reinforcement on the structural performance of the tested beams is analyzed. The study demonstrates the efficacy of Z-shape steel stirrups for the beam’s shear resistance, and the efficiency of prestressing GFRP and steel reinforcements on the beam’s load carrying capacity. It also shows the potential of SFRC for developing relatively lightweight prestressed structural elements without stirrups.
•We experimentally tested ten I-shaped concrete beams in a 4-point bending test.•Utilized hybrid prestressed steel and prestressed GFRP reinforcement.•beams made by normal concrete with z-stirrups, and 5 by SFRC without stirrups.•Discussed load-carrying capacity, failure modes, and ductility of tested beams.•Showed enhanced load-carrying capacity with prestressed GFRP and steel.
•RC-SFRC beams are designed according to fib Model Code 2010.•Design and numerical results exhibit similar results in terms of SLS and ULS.•The numerical model was able to capture the failure process ...of RC-SFRC beams.•The numerical tool can be used to optimize structural solutions of RC-SFRC beams.
In the preceding Part I of this study, an experimental program and numerical analyses using a multiscale model are performed to obtain the post-cracking parameters of steel fiber reinforced concrete (SFRC) through the simulation of three-point bending tests (3-PBT) according to EN 14651. In the present Part II, both numerical and experimental parameters obtained from the 3-PBT are used on the design of beams with combined reinforcement of steel fibers and rebars (RC-SFRC beams) according to fib Model Code 2010 in order to study their influence on the amount of bending and shear reinforcements required. In addition, the RC-SFRC beams designed are numerically simulated using the mesoscale model and the results are compared to the designed ones in terms of crack width, mean crack spacing, deflection and ultimate and service loads. The results demonstrated that computational simulations with an appropriated approach to represent the composite may be an important tool to contribute on the design of SFRC structural members.
According to the characteristics of steel fiber reinforced concrete (SFRC) with high tensile strength and carbon fiber reinforced plastic (CFRP) with high strength and light weight, a composite beam ...composed of CFRP plate, SFRC and ordinary concrete (OC) is developed in the paper. Eight specimens, including four CSOCBs with different heights of the SFRC and four SFRC–OC composited beams with varying heights of the SFRC, were tested to analyze the flexural behavior. The results show that the composite beam composed of OC, SFRC and CFRP improves the ultimate load capacity of the beam under unidirectional load, enhances the cracking and deformation resistance of the beam, and solves the defects of the weak tensile capacity of ordinary concrete beams. Applying them to the building structure can improve the stability of the structure and prolong the service life of the building. A prediction model for the bending capacity of the CSOCB was proposed and validated. Based on the limit state design method, the design formula for the bending capacity of the composite beam is described in detail herein.
•A composite beam composed of carbon fiber reinforced plastic (CFRP), steel fiber reinforced concrete (SFRC) and ordinary concrete (OC) was developed.•A prediction model for the bending capacity of the CSOCB was proposed and validated.•The design formula for the bending capacity of the composite beam is described based on reliability analysis.
In this study, several three-point-bending (TPB) experiments were conducted to investigate the influence of fiber content on the fracture behavior of hooked-end steel fiber-reinforced concrete ...(SFRC). Subsequently, a numerical meso-model was proposed based on the application of the cohesive/volumetric finite element method, which allows the pervasive fracture along non-prescribed trajectories to be captured accurately. The bond-slip relation and traction-separation relation of the fiber–concrete interface were both considered. Consequently, the accuracy of the meso-model was validated through the experiments conducted in this study. The influence of the separation angle of the SFRC fracture interface on the bridging effect of the fibers was investigated using the proposed model. Finally, based on the conclusions obtained from the experiments and meso-model, a macro-model of SFRC was proposed to improve the computational efficiency, which was validated considering two different experimental cases.
•Studies on the composition and typical properties of SFRC are systematically reviewed.•Problems and challenges of mesh-reinforced linings and usage of SFRC in tunnel linings.•Advantages, design ...considerations and practical performance of SFRC linings are discussed.
The complicated tunnelling conditions and variable engineering demands have made numerous challenges of mesh-reinforced lining structures. Thereafter, the steel fiber reinforced concrete (SFRC) is said to be a reliable alternative to mesh-reinforced linings. This paper reviews the constituent materials and typical properties of SFRC. The main causes of mesh-reinforced lining cracks or structure failures are summarized, and current challenges for mesh-reinforced linings are examined. Also, the advantages of using SFRC for the realization of the tunnel linings are highlighted. Furthermore, design considerations and some practical cases on application performance of SFRC in tunnel linings are summarized. This review confirmed the positive effect of SFRC lining on rock displacement control, lining pressure reduction, and global and local stability of the support structures. The research provides solid insights for promoting the development of SFRC in tunnel linings.
•A new parameter definition is proposed to evaluate the overall damage performance of PCCV.•A refined numerical model of PCCV is established.•The effect of prestress loss on performance of PCCV is ...considered.•The comparison of performance between containments with and without fiber reinforcement is conducted.
Current investigations cannot quantitatively predict the overall damage performance of prestressed concrete containment vessels (PCCVs) under internal pressure and the effect of steel fiber strengthening on the damage performance improvement has not been investigated. A new parameter definition is proposed to characterize the entire damage performance of conventional and steel fiber-reinforced concrete (SFRC) PCCVs under internal pressure in this study. The prestress loss is precisely calculated considering 40 years of the service period of PCCV. To review the possibility of operating lifetime extension of PCCV, the subsequent 60 years are also considered. Firstly, elaborate three-dimensional numerical models of conventional and SFRC containments were established. Then, three parameters to represent the extent corresponding to concrete, steel liner, and prestressed tendons of containment under damage were proposed. Finally, damage performance of conventional and SFRC containments considering the impact of prestress loss was discussed in depth. The results show that by introducing the SFRC and considering the five-year prestress loss, the pressure capacities for containment concrete, steel liner, and prestressed tendons are increased by 22.16%, 18.99%, and 12.35%, respectively. What's more, the proposed parameters can reflect the changing trend of the damage extent of containments under internal pressure and inclusion of steel fibers can improve damage performance significantly. To examine the realistic damage performance under internal pressure, the five-year prestress loss requires to be specifically considered.
•Steel fibers display better seismic performance over steel rebar in tunnel linings.•fr4-PGA-Probability of Seismic Damage relationships is proposed for SFRC tunnels.•A hybrid SFRC mix, with higher ...content of micro fibers, shows best seismic behavior.
In recent years, application of fibers as a replacement for conventional reinforcement in segmented lined tunnels has gained great interest due to resulting cost and time savings. In seismically active regions, the seismic vulnerability of underground tunnels is of great concern. The aim of this paper is to investigate the effects of different composites of Steel FRC (SFRC), as the tunnel’s lining material, on its seismic vulnerability, compared to each other and to that of unreinforced and conventionally reinforced concrete cases, employing analytical fragility curves. Results show that steel fibers, especially micro size fibers and for higher states of damage, display better seismic performance over conventional steel rebar in reinforced concrete linings. For best performance, a hybrid SFRC mix containing both micro and macro fibers, with a higher content of micro fibers over macro ones, is a technically preferable option for the design of segmental lining tunnels in seismic zones.
This study investigates the effects of concrete strength, steel fiber volume ratio, and steel fiber shapes on the flexural behavior and ductility of concrete beams reinforced with BFRP rebars under ...repeated loading with the aims of exploring the feasibility of using short discrete steel fiber to improve the ductility of beams, and proposing appropriate methods for evaluating their ductility. A four-point bending test was carried out on four steel fiber reinforced concrete (SFRC) beams with BFRP rebars and one beam reinforced with BFRP rebars only without steel fibers. Experimental results are reported in terms of the failure mode, flexural strength, load-deflection response, cracking behavior, and ductility, which reveals that the flexural strength of beams can be calculated using CSA S806-12 code method with an error of about 20%. Compared with ordinary concrete, the impact of steel fiber reinforcement on the service load of beams is more significant than that on their flexural strength; moreover, when steel fiber volume ratio increased from 0% to 1.0%, the deflection under service load decreased by 59.36%. In addition, the ductility of beam with 1.0% steel fiber volume ratio can be enhanced by 17% than that of concrete beam without steel fibers. Compared with energy ductility coefficient, displacement ductility coefficient, curvature ductility coefficient, the ductility coefficient of ACI 440.1R-15 prove to be more accurate in evaluating ductility of SFRC beams with BFRP rebars, and all the beams investigated in this study had a ductility factor greater than 4.0.
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