Numerical modeling of prestressed fiber reinforced high performance concrete beams subjected to shear (original) (raw)
Related papers
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.
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.
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 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 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...
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.
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 ...
Journal of civil engineering and architecture, 2015
Usage of fiber reinforced concrete to replace shear reinforcement has become more common in the precast industry in recent years. In some cases, the use of steel fibers could be problematic because of corrosion, hence, synthetic material could be a suitable alternative material solution. Thus, it would appear logical to undertake a comparison of these fibers' load bearing capacity to determine suitability in each case. In this paper, the bending and the shear tests of four large-scale and prestressed beams made of steel or synthetic fiber reinforced concrete without stirrups are presented. The post-cracking residual tensile strength diagram of the fibers, according to RILEM (International Union of Laboratories and Experts in Construction Materials, Systems and Structures) TC162, is given and the experimental behavior of the fiber solutions is compared. The modified fracture energy method is used to define an advanced material model for the fiber reinforced concrete in the finite element analysis. The numerical calculations and the test results are compared in terms of crack propagation and the loading-deflection process. As a consequence, both steel and synthetic fibers seem to be good alternatives to replace the stirrups. However, the behavior of each fiber is not the same. The numerical calculation provided a good approximation for the real scale tests.
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.
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.