An Investigation on Shear Behavior of Prestressed Concrete Beams Cast by Fiber Reinforced Concrete (original) (raw)
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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...
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...
Prestressed fiber reinforced concrete beams with reduced ratios of shear reinforcement
Cement and Concrete Composites, 1999
This paper presents an analysis of the influence of prestress and fibers on the shear behaviour of thin-walled I-section beams with reduced shear reinforcement ratio. Reduction of shear reinforcement in prestressed precast beams can make the reinforcement simpler and may increase the productivity in long line precasting beds. The use of short fibers can improve the shear strength and ductility. Nine concrete beams were built (six with prestressing forces) with three different mixtures: without fibers, with steel fibers, and with polypropylene fibers. Shear reinforcement ratios varied from 0 to 0.225% (geometric ratio). It was noted that prestressing increases cracking strength (both in bending and shear), extends the non-cracked area, and makes the compression struts less inclined. In the case of fiber reinforced concrete beams, control of cracking is more effective and consequently deflections are smaller. Ductility is also increased. Both fibers and prestressing reduce stresses in the stirrups and increase shear strength.
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.
Shear behaviour of fiber reinforced concrete beams
Cement and Concrete Composites, 1997
This paper presents the results of shearl'exure tests on steel and polypropylene fiber reinforced concrete beams. In addition to analyzing the influence of fibers on the structural peeormance in situations of di.erent ratios of shear reinforcement, some aspects of the properties of fresh and hardened concrete are introduced. Fourteen square-section beams were tested. The beams were prepared from seven different mix proportions, varying the type and the volume of fiber added. There were two beams for each composite mix: one model with and the other without stirrups. The main alterations resulting from the use of fibers were increased shear strength, stifj%ess (particularly after first cracking stage) and ductility. Other parameters used in analyzing performance were the properties of the hardened concrete (compressive strength, tensile strength, and modulus of elasticity), and stresses in the stirrups, in the longitudinal reinforcement and in the concrete (at the web and compression zone).
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.
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.
Shear Deformation of Steel Fiber-Reinforced Prestressed Concrete Beams
International Journal of Concrete Structures and Materials, 2016
Steel fiber-reinforced prestressed concrete (SFRPSC) members typically have high shear strength and deformation capability, compared to conventional prestressed concrete (PSC) members, due to the resistance provided by steel fibers at the crack surface after the onset of diagonal cracking. In this study, shear tests were conducted on the SFRPSC members with the test variables of concrete compressive strength, fiber volume fraction, and prestressing force level. Their localized behavior around the critical shear cracks was measured by a non-contact image-based displacement measurement system, and thus their shear deformation was thoroughly investigated. The tested SFRPSC members showed higher shear strengths as the concrete compressive strength or the level of prestress increased, and their stiffnesses did not change significantly, even after diagonal cracking due to the resistance of steel fibers. As the level of prestress increased, the shear deformation was contributed by the crack opening displacement more than the slip displacement. In addition, the local displacements around the shear crack progressed toward directions that differ from those expected by the principal strain angles that can be typically obtained from the average strains of the concrete element. Thus, this localized deformation characteristics around the shear cracks should be considered when measuring the local deformation of concrete elements near discrete cracks or when calculating the local stresses.
Shear Behavior of Fiber-Reinforced Concrete Beams: An Experimental Study
International Journal of GEOMATE, 2021
Eight steel fiber-reinforced normal strength concrete beams (200 mm wide, 250 mm deep and 1500 mm long) were tested in bending under two concentrated loads, without and with stirrups. The concrete beams were designed to have marked shear behavior. Three types of steel fibers (SFs), straight, hooked and corrugated, were investigated as a possible replacement for standard transverse reinforcement. The fiber volume content, the aspect ratio of fibers, and the existence of stirrups were the major testing parameters in this regard. Four fiber volume proportions (R f of 0%, 0.5%, 1.0% and 1.5%) and three aspect ratios (l/d of 50, 55 and 60) were utilized. According to the experimental data, the shear behavior of steel fiber-reinforced normal strength concrete beams (SFRCBs) without stirrups was similar, if not superior, to that of normal strength concrete beams (RCBs) with stirrup reinforcement. The SFRCBs displayed extremely thin diagonal cracks and higher shear strengths, especially for fiber fractions of 1% and 1.5%. The experimental results were compared to major universal codes and existing models from the literature. The major codes undervalue the concrete contribution to shear strength while exaggerating the contribution of the stirrups. Furthermore, some of the existing models overestimate the fibers' contribution to the shear strength, while others underestimate it when compared to the present experimental findings.
Shear Strength of Prestressed Steel Fiber Concrete I-Beams
International Journal of Concrete Structures and Materials, 2015
Six full-scale prestressed concrete (PC) I-beams with steel fibers were tested to failure in this work. Beams were cast without any traditional transverse steel reinforcement. The main objective of the study was to determine the effects of two variables-the shear-span-to-depth ratio and steel fiber dosage, on the web-shear and flexural-shear modes of beam failure. The beams were subjected to concentrated vertical loads up to their maximum shear or moment capacity using four hydraulic actuators in load and displacement control mode. During the load tests, vertical deflections and displacements at several critical points on the web in the end zone of the beams were measured. From the load tests, it was observed that the shear capacities of the beams increased significantly due to the addition of steel fibers in concrete. Complete replacement of traditional shear reinforcement with steel fibers also increased the ductility and energy dissipation capacity of the PC I-beams.