SFRC Slabs Research Articles

Influence of fiber orientation on flexural‐based design of steel fiber‐reinforced concrete slabs: Experimental and numerical program

AbstractSteel fiber‐reinforced concrete (SFRC) has proven to be a suitable structural material for constructing elevated flat slabs, and several existing office and residential buildings, in which SFRC was used for these components, highlighted the positive outcomes from both technical and sustainability perspectives. However, research on the influence of fiber orientation on the flexural performance of SFRC slabs is relatively scarce despite the fact that a number of studies revealed that the use of constitutive models derived from three‐point bending tests on notched beams leads to overestimations of the bearing capacity of statically indeterminate slabs. In this context, this study aims at presenting an extensive experimental program that consisted of testing three SFRC slabs (3.0 × 3.0 × 0.1 m3) subjected to point load under a statically indeterminate test configuration. The testing procedure was followed by the extraction of 88 cores in order to analyze both fiber distribution and orientation by means of a non‐destructive inductive method. The results indicate that lower orientation numbers were observed in cylinders drilled from the slabs in comparison with those observed in the 150 × 150 × 600 mm3 notched reference beams tested to characterize the pre‐ and post‐cracking flexural performance of the SFRC produced. Based on these results, a straightforward design‐oriented approach to compute an orientation factor was proposed and considered to develop the constitutive law used to simulate the structural response of SFRC slabs by means of nonlinear finite element model. The numerical simulation results showed a good agreement with the experimental response, this evidencing that the orientation factor may permit to account for the differences caused by geometric and statistical scale‐induced factors between both the beams used for the SFRC flexural properties characterization and slabs produced with the same SFRC.

Experimental Investigation on the Impact of Micro-Steel Fibers on the Flat Slabs' Punching Shear Resistance

This research examined the effects of micro-straight steel fiber percentage and column form on the punching shear of SFRC slabs. Fibers made of micro steel with a diameter of 0.2 mm and a length of 13mm with an aspect ratio equal to 65 were used. The fiber content varied between 0.5%, 1%, and 1.5% by volume. Four different types of concrete mixes were adopted and tested. Experimental results showed that when the percentage of steel fibers in SFRC increased, its compressive strength, flexural strength, splitting tensile strength, and direct tensile strength improved. This investigation applied a monotonic load to eight cast slabs (two each of conventional concrete of square and circular column sections of the equivalent area while the other six slabs were made with steel fiber concrete. The dimensions of each slab were (920 x 920 x 80 ) mm. Each slab specimen had essential, edge-based support with square and round column sections. It has been demonstrated that slabs with square column sections endured a relatively higher ultimate load than slabs with circular column segments when the steel fiber dosage was 0.5% or 1.0%. Still, at a steel fiber dosage of 1.5%, circular column segment slabs approached the ultimate load of square column segment slabs. The heterogeneous behavior in concrete can be attributed to the random and unequal distribution of steel fibers throughout the material. There were only flexural fractures visible on the tensile face of the slab. New fractures emerged in the center of the slab as the load increased.

Proposta para estimativa de capacidade de carga na punção de lajes lisas de concreto armado reforçado com fibras de aço

abstract: This paper proposes an adjusted function for estimating the punching shear load-carrying capacity of concrete flat slabs without shear reinforcement according to the Brazilian standard code. The Adjusted function considers the influence of the steel fiber content. Data from 68 steel fiber reinforced concrete slabs (SFRC slabs) were used, simulating the connection of flat slabs with square section columns. These slabs were obtained from a study conducted by 14 different researchers. The parameters used for the adjusted function were the fiber content and the compressive strength of the concrete. The adjusted function was obtained by curve-fitting. The result from the adjusted function shows a relation in the order of 1.3 between the experimental rupture load and the calculated load, a value close to that already obtained by the normative text when the calculation is for conventional concrete. This shows that the proposal presented here keeps the same level of security with a confidence index of 96% in comparison with other authors’ models presented in this study.

Correction to: A thermo-mechanical model for SFRC beams or slabs at elevated temperatures

The article A thermo-mechanical model for SFRC beams or slabs at elevated temperatures, written by Peter Heek. Jasmin Tkocz. Peter Mark.

Biaxial bending of SFRC slabs: Is conventional reinforcement necessary?

Fibre reinforced concrete shows enhanced performance in statistically redundant bi-dimensional structural elements that undergo biaxial bending. However, the lack of reinforcing rebars in fibre reinforced structural elements may affect the structural ductility which may further affect the overall load bearing capacity of these structures. To investigate the influence of fibres in such elements, six concrete plates of 2000 × 2000 × 150 mm reinforced with steel fibres and/or reinforcing rebars are tested under a central concentrated load. Two of the elements are reinforced with only 35 kg/m3 of steel fibres, two are reinforced with 2-way conventional reinforcing rebars (35 kg/m3, in each direction) and two are reinforced with both steel fibres and rebars. The specimens are simply supported at the middle of each side by means of a bilateral restraint; the deflection response and cracking behaviour of all the specimens are recorded and compared. Moreover, the methodology introduced in the fib Model Code 2010 for design of steel fibre reinforced concrete is implemented to predict the ultimate load bearing capacity of these elements and its reliability is determined in comparison with the experimental values. The comparison of the behaviour of the specimens reinforced only with steel fibres, with those reinforced with steel rebars, shows the higher efficiency of steel fibres in terms of load carrying capacity, but with a lower ductility. The combination of steel fibres and rebars allows for a better exploitation of the capacity of both reinforcement solutions. Finally, the reliability of the approach implemented for the ultimate load prediction is shown and the need of rebars in providing ductility in fibre reinforced concrete members is underlined.

Experimental study on evaluation of the fatigue resistance of SFRC slabs which blended steel fiber in the ordinary portland cement

Experimental study on evaluation of the fatigue resistance of SFRC slabs which blended steel fiber in the ordinary portland cement

Shear in SFRC Slabs Reinforced with High-Strength Steel

Shear in SFRC Slabs Reinforced with High-Strength Steel

Fracture behavior of SFRC slabs on grade

Fracture behavior of SFRC slabs on grade

Fracture behavior of SFRC slabs on grade

In concrete pavements, steel fibers are particularly suitable both for limiting shrinkage effects and for increasing the bearing capacity and fatigue resistance. In the present paper, the fracture behavior of steel-fiber-reinforced concrete slabs on grade is studied by using Non Linear Fracture Mechanics FE analyses, based on both smeared and discrete crack models. The fracture mechanics models have been validated by results from experiments on full scale slabs on elastic soil subjected to a load in the slab center. The comparison shows that NLFM analyses closely predict crack development, ultimate load and the collapse mechanism of slabs on grade. The smeared crack approach has been used for studying different loading conditions since it does not need an a-priori knowledge of the crack pattern.