Shear Strength of Prestressed Steel Fiber Concrete I-Beams (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...
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.
Simulation of Prestressed Steel Fiber Concrete Beams Subjected to Shear
International Journal of Concrete Structures and Materials
This paper developed an analytical software, called Simulation of Concrete Structures (SCS), which is used for numerical analysis of shear-critical prestressed steel fiber concrete structures. Based on the previous research at the University of Houston (UH), SCS has been derived from an object-oriented software framework called Open System for Earthquake Engineering Simulation (OpenSees). OpenSees was originally developed at the University of California, Berkeley. New module has been created for steel fiber concrete under prestress based on the constitutive relationships of this material developed at UH. This new material module has been integrated with the existing material modules in OpenSees. SCS thus developed has been used for predicting the behavior of the prestressed steel fiber concrete I-beams and Box-beams tested earlier in this research. The analysis could well predict the entire behavior of the beams including the elastic stiffness, yield point, post-yield stiffness, and maximum load for both web shear and flexure shear failure modes.
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 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...
Experimental investigation of shear-critical prestressed steel fibre reinfocred concrete beams
2018
This paper presents the experimental results of prestressed steel fibre reinforced concrete (SFRC) beams and it compares analytical model predictions with these results. Six beams were subjected to a force-controlled four-point bending test until failure. The three investigated parameters were the fibre dosage, the amount of prestressing force and the presence of shear reinforcement. During the test, failure mode and load, as well as deformations, displacements and cracking pattern properties were observed by means of conventional measurement devices and advanced optical techniques, including Bragg grated optical fibres and digital image correlation technique. Additionally, material properties were determined according to standardized European tests. The experimental results were compared to analytical predictions according to shear design equations in Model Code 2010. For the six beams, an average experimental-to-predicted failure load ratio of 1.43 was found with a coefficient of variation of 7.2%. Furthermore, four other analytical models for shear design of SFRC are investigated, namely DRAMIX Guideline, RILEM TC 162-TDF sigmaepsilon method, CNR-DT 204/2006 model and a model proposed by Soetens. All models underestimate the shear capacity of prestressed SFRC beams. The underestimation increases for a higher prestress level, whereas the correlation with the fibre dosage varies within the models.
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.
Behaviour of Prestressed Ultra-High Performance Concrete I-Beams Subjected to Shear and Flexure
2013
Ultra-high performance concrete (UHPC) is a new type of concrete developed by selecting the particle sizes and gradation in the nano-and micro-scales targeting the highest possible packing. The resulting concrete with very high density is called UHPC. UHPC has very low permeability and hence it is very highly durable compared to traditional or high performance concrete (HPC). Micro reinforcement of UHPC by random distributed steel-synthetic fibers results in superior mechanical properties such as very high compressive and tensile strengths, high ductility, and high fatigue resistance. The material selection and early age curing processes, use of fiber reinforcement, and very high quality in production resulted in a very high initial cost of UHPC structures. In order to enable the mass production and cost effective use of the material, performance based design and optimization of UHPC structural members are required. This study is part of an NRC Canada research project to develop innovative, cost effective, and sustainable bridge structural systems using UHPC and other innovative materials. In this study, the estimation of shear and flexural capacities using the available approaches of international design guidelines of UHPC structures are comprehensively compared to a proposed truss models, linear and nonlinear finite element models. Several design trials intended to allow for an optimized use of the materials and a maximum load capacity was conducted for simply supported beams with one or two external loads, and having rectangular or I cross sections. Linear and non-linear finite element models are developed and their results were compared to the available international design recommendations. Truss models are proposed to simplify the stress analysis in the shear zone of the prestressed UHPC beams.
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.