Shear Deformation of Steel Fiber-Reinforced Prestressed Concrete Beams (original) (raw)
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Engineering Structures, 2019
The effect of steel fiber reinforcement on the shear behavior of prestressed concrete beam is studied using digital image correlation (DIC) technique. Steel fiber reinforced prestressed concrete (SFRPC) beams with fiber dosages of 0.5% and 1.0% by volume were cast and tested under shear. SFRPC beams were tested under a three-point bending configuration at a shear span (a) to depth (d) ratio of 2.4 to simulate shear dominant behavior. Other parameters such as compressive strength of concrete, prestressing reinforcement ratio and level of prestressing were kept constant. The kinematics of diagonal shear cracks including crack opening and crack slip were monitored using DIC based full-field strain measurement technique. The improvement in aggregate interlock and residual tensile strength at the crack tip due to the addition of steel fiber was reflected in the post-peak response of SFRPC beams. DIC analysis revealed that the full depth crack was formed in all the SFRPC beams before reaching their peak loads. The dilatant behavior was found to be consistent for all the test specimens (control and fiber reinforced concrete beams) up to peak load. The test results portray that the addition of steel fibers stiffens the post-peak response and reduces the crack opening and crack slip. Moreover, the failure mode changed from shear (brittle) to flexure-shear (less brittle) mode.
An Investigation on Shear Behavior of Prestressed Concrete Beams Cast by Fiber Reinforced Concrete
Arabian Journal for Science and Engineering, 2018
Failure due to shear is brittle in nature, and inherent lesser concrete tensile strength is a main contributing factor. During loading before the shear reinforcement could start functioning, cracking in concrete starts. Use of fibers in concrete had proven improved impact on tensile strength of concrete. Active reinforcement role initiates after concrete cracking starts. This paper investigates into the shear behavior of fiber reinforced, pretensioned concrete I-section beam specimens. A total of six beam specimens were cast. Two types of fibers, steel fibers and polypropylene fibers were used in five different proportions. For comparison, one control specimen was also cast without inclusions of fibers in concrete. Concrete mix ratio, prestress force, shear span-to-depth ratio and shear and flexural reinforcement details were kept constant in all specimens. Specimens were subjected to four-point loading to ensure that all specimens fail due to excessive shear force. During tests, deflections and strains were also measured. It was concluded that shear strength of beams was improved using steel fiber reinforced concrete (SFRC) as compared to polypropylene fiber reinforced concrete (PPFRC). SFRC beam containing 0.65% fiber depicted 50.71% improvement in ultimate failure load, 67% improvement in first cracking load and 36% improvement in ultimate deflection as compared to control beam.
Shear Behavior of Steel Fiber Reinforced Precast Prestressed Concrete Beams
2018
Precast industries constantly look for better alternative solutions to reduce the secondary reinforcement to speed up the production process. Addition of fibers in concrete helps in reducing the use of secondary reinforcement. Presence of fiber reinforcement has proven to enhance the ductility and energy dissipation capacity of the concrete under flexure and shear. Shear behavior of concrete members mainly depends on the compressive strength of concrete, shear span to depth ratio (a/d), amount of stirrups, aggregate interlock and dowel action of longitudinal reinforcement. The present study focuses on the shear behavior of steel fiber reinforced PSC beams with different volume fractions i.e., 0.50% and 1.00%. Fiber reinforced prestressed concrete (FRPC) beams were cast using long line method and tested with a shear span to depth ratio of 2.4 to simulate shear dominant behavior. Strain gauges were attached to the strands at loading point and at the center of shear span (a/2) to measu...
Cement & Concrete Composites, 2002
This paper presents an assessment of the flexural behavior of 15 fully/partially prestressed high strength concrete beams containing steel fibers investigated using three-dimensional nonlinear finite elemental analysis. The experimental results consisted of eight fully and seven partially prestressed beams, which were designed to be flexure dominant in the absence of fibers. The main parameters varied in the tests were: the levels of prestressing force (i.e, in partially prestressed beams 50% of the prestress was reduced with the introduction of two high strength deformed bars instead), fiber volume fractions (0%, 0.5%, 1.0% and 1.5%), fiber location (full depth and partial depth over full length and half the depth over the shear span only). A three-dimensional nonlinear finite element analysis was conducted using ANSYS 5.5 [Theory Reference Manual. In: Kohnke P, editor. Elements Reference Manual. 8th ed. September 1998] general purpose finite element software to study the flexural behavior of both fully and partially prestressed fiber reinforced concrete beams. Influence of fibers on the concrete failure surface and stress–strain response of high strength concrete and the nonlinear stress–strain curves of prestressing wire and deformed bar were considered in the present analysis. In the finite element model, tension stiffening and bond slip between concrete and reinforcement (fibers, prestressing wire, and conventional reinforcing steel bar) have also been considered explicitly. The fraction of the entire volume of the fiber present along the longitudinal axis of the prestressed beams alone has been modeled explicitly as it is expected that these fibers would contribute to the mobilization of forces required to sustain the applied loads across the crack interfaces through their bridging action. A comparison of results from both tests and analysis on all 15 specimens confirm that, inclusion of fibers over a partial depth in the tensile side of the prestressed flexural structural members was economical and led to considerable cost saving without sacrificing on the desired performance. However, beams having fibers over half the depth in only the shear span, did not show any increase in the ultimate load or deformational characteristics when compared to plain concrete beams.
Shear Behavior of Steel Fiber Reinforced Prestressed Concrete Beams
2020
Prestressed concrete girders are the main superstructure elements in many bridge structures. Shear failures in these girders are undesirable due to brittle failure and little warning time. To prevent shear controlled brittle failure, it is normal practice to increase the amount of transverse reinforcement in flexural members. However, past studies have revealed that even higher transverse reinforcement ratios (i.e. > 4%) may not be able to eliminate shear failure in some cases. Moreover, the increased reinforcement makes it more difficult to place and consolidate the concrete. This research program aimed to investigate the feasibility of replacing traditional shear reinforcement in prestressed concrete beams with steel fibers. A total of 14 rectangular and 8 I-shaped prestressed concrete beams were investigated after subjecting them to two-point loading test. The beams were casted with steel fiber ratios ranging from 0.75% to 2.00%. Experimental results revealed that the inclusio...
2016
Although the use of fibre reinforced concrete (FRC) for structural applications is continuously increasing, it is still limited with respect to its potentials. This can be mainly attributed to the lack of international building codes for FRC structural elements. This paper aims to contribute to the development of suitable design principles for shear in FRC elements by presenting the preliminary results of 6 full-scale pretensioned steel-fibre reinforced concrete members. The main investigated parameters are the amount of prestressing, the amount of shear reinforcement and the fibre dosage respectively. All specimens are subjected to a four-point bending test until failure. Traditional mechanical measurement devices are used in combination with advanced optical measurement systems (i.e. stereo-vision digital image correlation 3D-DIC and Bragg grated optical fibres). Apart from the full-scale tests, a number of small-scale experimental investigations are performed to characterize the material properties. The experimentally determined results are compared to predictions using analytical models found in Eurocode 2 and Model Code 2010.
Cement & Concrete Composites, 2004
This study presents results from an experimental program for eight fully prestressed beams and seven partially prestressed beams made with high strength fiber-reinforced concrete (plain concrete strength of 65 MPa). These studies mainly attempted to determine the influence of trough-shaped steel fibers in altering the flexural strength at first crack and ultimate, the load–deflection and moment–curvature characteristics, ductility and energy absorption capacity of the beams. The magnitude of the prestress, volume fraction of the fibers ranging from 0% to 1.5% and the location of fibers were the variables in the test program.Analytical models to determine the load–deflection and moment–curvature relationships as a function of the fiber volume fraction have been formulated. Empirical relationships for the ultimate strength, first crack load level, load versus deflection and moment versus curvature as a function of fiber content have been proposed by making use of force equilibrium and compatibility considerations.A primary finding emerging from the experimental program was that the placement of fibers over a partial depth in the tensile side of the prestressed flexural structural members provided equivalent flexural capacity as in a beam having the same amount of fiber over the full cross-section. In large scale precast concrete applications it is expected that this would be economical and lead to considerable cost saving in the design without sacrificing on the desired structural performance. The analytical models proposed in this study predicts the test results closely.
Analysis of prestressed fibre-reinforced concrete beams
Proceedings of the ICE - Bridge Engineering, 2009
This paper presents the test results of 12 partially prestressed concrete flexural beams reinforced with steel fibres that failed in flexure over partial or full depth. The variables considered were strength grades of concrete (35, 65 and 85 MPa) and the presence of steel fibres in the cross-section of the beam (web, flange or full depth). Three-dimensional finite element analysis of the prestressed beams was carried out to assess the non-linear behaviour of concrete, for example post-peak softening, concrete cracking strain softening, tension stiffening, bond-slip and yielding of reinforcement. Also, the effects of the addition of steel fibres in the concrete (increase in tensile strength and control of crack width due to the bridging of fibres across the crack interface) were modelled. The bond-slip behaviour of longitudinal reinforcements (steel fibres, prestressing wire and deformed bars) was accounted for to capture the structural stiffness of the concrete beam accurately. The ...
Shear Performance of Pretensioned Prestressed Concrete Beam with Steel Fibre
IOP Conference Series: Materials Science and Engineering
The use of steel fibre has proven to be effective in enhancing the performance of concrete structure. However, its application in the prestressed concrete is not fully understood. Therefore, this study presents the application of steel fibre in the prestressed concrete beam. An investigation on the crack pattern and load-deflection relationship of prestressed concrete beam filled with steel fibre was carried out and a comparison is made with the prestressed concrete beam without the steel fibre. A total of three configurations of beams with size of 150 × 200 × 1200 mm were employed. Steel fibres were added with two different volume fractions of 3% and 5%. Experimental results showed that the control beam experienced shear crack pattern, while the other two beams experienced the flexural-shear crack. In comparison between two different percentages of steel fibre in the beam configurations, more cracks were observed in the prestressed beam that filled with 3% steel fibre compared to the prestressed beam filled with 5% of steel fibre.
Several experimental tests have demonstrated the effectiveness of steel fibers in substituting the minimum code required shear reinforcement in beams, particularly in precast high performance concrete structures. Despite the large number of experimental results available, only a few numerical studies have been so far published concerning fiber reinforced concrete structures. The behavior of full scale steel fiber reinforced concrete beams is herein analysed using a smeared crack damage model provided by the latest release of ABAQUS (V. 6.3). The numerical model is validated against the experimental results obtained on full scale FRC beams. The numerical results allow to correctly predict the experimental response, particularly with respect to the first cracking point, the initial crack pattern, and its development. The results allow a better understanding of fiber reinforced concrete structures under shear loading and will be used as a basis for developing a new design procedure for such kind of structures.