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Effect of the Notch-to-Depth Ratio on the Post-Cracking Behavior of Steel-Fiber-Reinforced Concrete
Abstract and Figures
Concrete barely possesses tensile strength, and it is susceptible to cracking, which leads to a reduction of its service life. Consequently, it is significant to find a complementary material that helps alleviate these drawbacks. The aim of this research was to determine analytically and experimentally the effect of the addition of the steel fibers on the performance of the post-cracking stage on fiber-reinforced concrete, by studying four notch-to-depth ratios of 0, 0.08, 0.16, and 0.33. This was evaluated through 72 bending tests, using plain concrete (control) and fiber-reinforced concrete with volume fibers of 0.25% and 0.50%. Results showed that the specimens with a notch-to-depth ratio up to 0.33 are capable of attaining a hardening behavior. The study concludes that the increase in the dosage leads to an improvement in the residual performance, even though an increase in the notch-to-depth ratio has also occurred.
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... Diversos factores influyen en el comportamiento del HRF: el material, la forma de las fibras, la dosificación y su orientación en el elemento estructural (Martinie (Sarmiento et al., n.d.) (Yoo et al., 2016) (Marcos García Alberty, 2015) (Aguilar et al., 2021) (Zerbino, n.d.). ...
Durante los últimos 60 años la utilización de hormigones reforzados con fibras (HRF) ha tenido una constante evolución. Esta técnica permite la reducción del armado tradicional mediante barras de acero en el diseño estructural de obras civiles y de edificación. Las fibras empleadas desde el principio del uso de esta técnica han sido las de acero, pero en estos últimos años otras fibras sintéticas se han abierto paso en los HRF. Así las macro fibras de poliolefina han demostrado cumplir con los requerimientos necesarios para ser consideradas aptas en el diseño estructural. Pero este avance tecnológico de las fibras de poliolefina debe venir apoyado con el conocimiento profundo de sus características y la forma como estas se distribuyen dentro de los elementos estructurales . Por tal motivo, en el presente estudio se analiza la distribución de las fibras a través del coeficiente de orientación para elementos de hormigón reforzados con fibras de poliolefina (HRFP) sometidos a ensayos de fractura a modo mixto, los resultados indican que este tiende a disminuir con relación a un plano vertical.
The most frequently used construction material in buildings is concrete exhibiting a brittle behaviour. Adding fibers to concrete can improve its ductility and mechanical properties. To this end, a laboratory study was conducted to present an experimental model for the specimens’ size effect of on macro-synthetic fiber-reinforced concrete using variations in fracture energy. Composite concrete beams with different thicknesses and widths were made and tested under mode I to obtain (1) fracture toughness, (2) fracture energy, and (3) critical stress intensity factor values. Results indicated that by increasing the thickness and the width, fracture toughness and fracture energy were enhanced. Moreover, increasing the thickness and width of the beam led to critical stress intensity factors enhancement respectively by 35.01–41.43% and 7.77–8.09%.
This article reports the effect of notch to depth ratio (α) and steel fiber volume fraction (Vf) on Acoustic Emissions (AE) generated during Mode I fracture process in Steel Fiber Reinforced Concrete (SFRC). The Plain Concrete (PC) and SFRC Three-Point Bend (TPB) specimens were tested by following EN: 14651-2005, RILEM TC 162-TDF, RILEM TC FMC-50 and JCI-S-001-2003 by CMOD control. Simultaneously, the AE signal waveforms were recorded by using eight AE channel monitoring system. The 2D surface strains and displacements were also recorded using Digital Image Correlation (DIC) technique. The spikes in the cumulative AE energy versus time plot were observed at the instants where sudden drops in the post peak load carrying capacity occurred. Peak load, Fracture energy, AE energy and post peak ductility decreased with increasing α value . The fiber bridging mechanism in SFRC was explored using the concept of crack kinematics with the DIC technique.
Pervious concrete is one of essential components in construction of sponge city, and the current study mainly focuses on the fracture performance of such promising material. Combined with three-point-bending (3-p-b) tests, a new method is proposed to determine the fracture properties of pervious concrete on the basis of Boundary Effect Model (BEM). The effects of material micro-structures (pore structure, aggregate structure) and specimen geometries on the fracture of pervious concrete are incorporated into the proposed formula in the form of fictitious crack. Then four groups of 3-p-b test results are collected to verify the proposed methods. The results show that the fracture properties obtained are independent of the specimen geometries, but are significantly influenced by the micro-structure of pervious concrete. The pervious concrete is strengthened with the increase of aggregate sizes, but is weakened with the increase of voids contents. Taking into account all the conclusions offered above, the fracture properties are strongly suggested to be carefully considered during the design of pervious concrete structures.
Critical investigation for M-40 grade of concrete having mix proportion 1:1.43:3.04 with water cement ratio 0.35 to study the compressive strength, flexural strength, Split tensile strength of steel fibre reinforced concrete (SFRC) containing fibers of 0%, 1%, 2% and 3% volume fraction of hook tain. Steel fibers of 50, 60 and 67 aspect ratio were used. A result data obtained has been analyzed and compared with a control specimen (0% fiber). A relationship between aspect ratio vs. Compressive strength, aspect ratio vs. flexural strength, aspect ratio vs. Split tensile strength represented graphically. Result data clearly shows percentage increase in 28 days Compressive strength, Flexural strength and Split Tensile strength for M-40 Grade of Concrete.
One of the most important and widely used construction materials of modern times is concrete. A lot of effort has been made in recent years to study the material and all its related technologies. An example of this is fastening systems which are widely used. Due to their importance regarding the safety of structures and people, numerical models which are able to predict the complex behaviour of such systems were developed. This paper endeavors to promote the application of advanced concrete models by providing a comprehensive set of concrete test data, cast from the same batch. These test data are available for model development, calibration , and validation. Flexure tests of four sizes, confined and unconfined compression tests, as well as Brazilian splitting tests of five sizes, and loading and unloading data are included in the database available at http://www.baunat.boku.ac.at/comprtest.html. For all specimen sets the nominal stress-strain curves and crack patterns are provided.
Steel fibers are added to concrete due to its ability to improve the tensile strength and control propagation of cracks in reinforced concrete members. Steel fiber reinforced concrete is made of cement, fine, water and coarse aggregate in addition to steel fibers. In this experimental work, flexural cracking behavior of reinforced concrete beams contains different percentage of hooked-end steel fibers with length of 50 mm and equivalent diameter of 0.5 mm was studied. The beams were tested under third-point loading test at 28 days. First cracking load, maximum crack width, cracks number, and load-deflection relations were investigated to evaluate the flexural cracking behavior of concrete beams with 34 MPa target mean strength. Workability, wet density, compressive and splitting tensile strength were also investigated. The results showed that the flexural crack width is significantly reduced with the addition of steel fibers. Fiber contents of 1.0% resulted in 81% reduction in maximum crack width compared to control concrete (without fiber). The results also showed that the first cracking load and maximum load are increased with the addition of steel fibers.
Structures are often subjected to extreme loading conditions that lead to their premature deterioration, and replacement of those structures before the end of their design lives is very expensive. The rehabilitation of deteriorated structures by using externally bonded fibre-reinforced polymer (FRP) composites is gaining popularity in the construction sector owing to its high strength, optimum durability and compatibility with concrete structures during application. This paper aims to review the current state-of-the-art on the performances, challenges and future opportunities of FRP-strengthened reinforced concrete (RC) structures under different loading scenarios. FRP strengthening leads to satisfactory performances under static, dynamic and extreme environmental conditions. Debonding and FRP rupture are the common types of failure observed, however, the failure mechanisms operating under the combined action of service loads and environmental exposures are still unclear. The acceptance and application of FRPs in strengthening RC structures will further increase upon developing techniques for utilising the full FRP strength, reducing the brittleness, risk of fires and accidental damage, minimising the energy consumption as well as carbon emission during production, and reducing the high initial cost. This paper also identifies the gaps in the present state of knowledge and the potential research directions for FRP-strengthened structures that lead to better understanding and establishment of design guidelines.
This paper discusses an experimental investigation on the tension stiffening effect on reinforcing bars embedded in plain concrete and steel fiber‐reinforced concrete ties. The experimental campaign, carried out in the Laboratory of the University of Rome Tor Vergata, involved 10 specimens with a square cross‐section of 150 mm × 150 mm and a length of 3,000 mm, with a 3,700‐mm‐long conventional reinforcing bar embedded in the middle of the cross‐section. The cracking behavior of the element was investigated varying the main parameters, such as the fiber volume, the maximum aggregate size, and the diameter of the steel reinforcement. The outcomes of the performed tests have shown the effectiveness of steel fiber‐reinforced concrete in controlling the crack pattern of reinforced concrete structures. Furthermore, the obtained results represent a useful reference point for improving provisions given by standards for tension stiffening, crack spacing, and crack opening for steel fiber‐reinforced concrete members.
The post‐cracking tensile behavior of polypropylene fiber reinforced concrete (PFRC) was investigated through an experimental study; special attention was devoted to the effects of fiber distribution and orientation on samples performance. In this regard, an experimental campaign based on uniaxial tensile tests (UTTs) on notched cylinders as well as three‐point bending tests (3PBTs) on notched beams was carried out. Uniaxial post‐cracking tensile laws retrieved both directly (UTTs) and indirectly (3PBTs) were compared. In the latter case, the fracture energy was higher because of the strongly dependency between PFRC post‐cracking performance and fiber distribution and orientation. In addition to cast cylindrical samples, core samples were directly drilled from the beams and tested under UTTs in order to compare their post‐cracking performance with that obtained by flexural standard tests on notched beams.
The bond characteristics between steel fiber and a cementitious matrix play a crucial role in controlling the performance of steel fiber-reinforced concrete (SFRC). The bonding mechanisms of SFRC have attracted considerable attention over the last four decades and are still active research. This overview provides a state-of-the-art understanding of the major mechanisms governing the pullout behavior of steel fibers. Characteristics of different types of bond and their functions have been explained in detail. Primarily important are bond strength in each of its likely failure modes. Different factors affecting the bond strength include geometry, orientation and embedded length of fiber as well as matrix strength. A review of existing analytical papers investigates the bond mechanisms between steel fiber and cementitious matrix. The review shows that the most successful method to improve bond slip is to reinforce concrete with pre-deformed fibers. This review also provides useful information on how fiber geometry influences pullout behavior from the matrix for a known relative strength between the two constituents. The theory of bonding and its related parameters is surveyed. Finally, recommendations for future research and optimum applications of SFRC are considered.
The book presents the underlying theories of the different approaches for modeling cracking of concrete and provides a critical survey of the state-of-the-art in computational concrete mechanics. It covers a broad spectrum of topics related to modeling of cracks, including continuum-based and discrete crack models, meso-scale models, advanced discretization strategies to capture evolving cracks based on the concept of finite elements with embedded discontinuities and on the extended finite element method, and extensions to coupled problems such a hygro-mechanical problems as required in computational durability analyses of concrete structures.
This study thoroughly investigated the flexural behaviour of phenolic cored sandwich beams with glass fibre composite skins in the horizontal and vertical positions. The beams have a shear span-to-depth ratio (a/d) varying between 0.5 and 12, and tested under 4-point static bending. Their failure load are then predicted theoretically. The results showed that changing the beam orientation from horizontal to vertical changes the failure mode from brittle to progressive. The sandwich beam’s high bending stiffness can be efficiently utilised by placing them vertically. The a/d ratio played a major role on the load capacity and failure mode. In both orientations, the load capacity decreased with the increased of a/d. The beam failed in shear, a combined shear and bending, and bending for a/d ≤ 2, 2 < a/d < 6, and a/d ≥ 6, respectively. These failure mechanisms can be correlated to the shear-to-bending stress ratio while the failure load can be reasonably predicted using the available theoretical models. The two-way analysis of variance showed that the beam orientation is a more influential parameter than the a/d ratio. From this study, the horizontal beams are preferable for flexural dominated structures while the vertical beams are desirable for shear dominated structures.