Biaxial bending of SFRC slabs: Is conventional reinforcement necessary?

Abstract

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 9 2000 9 150 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/m 3 of steel fibres, two are reinforced with 2-way conventional reinforcing rebars (35 kg/m 3 , 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.

Fiber reinforced concrete: from flexural tests to solid slabs

“…Overall, slabs reinforced only with fibres may show limited ductility as opposed to R/C slabs, which needs attention when dealing with slabs without conventional reinforcement and where ultimate limit state is of concern. This was shown earlier in [6] where the behavior of SFRC slabs and R/C ones where compared. The results presented here show that for SFRC slabs, determination of the maximum deflection may also be subjected to a rather high uncertainty.…”

“…However, measurements on the rotation of the slab corners showed that for the most part of the test, the anchorage device is not in tension, and in fact the slabs are allowed to rotate at the supports. The details on the support dimensions and placement can be found in [6]. A schematic representation of the slab setup is shown in Figure 1.…”

“…This evidence draws attention to the importance of adopting a proper failure mechanism when performing a yield line approach. Measures should be taken to assure sufficient structural ductility so that the predicted failure mechanism, conforms with the real-life crack patterns [6]. Nevertheless, in a monolithic structure the support rigidity may suffice to trigger the creation of negative cracks.…”

Effects of Low Temperatures on Flexural Strength of Macro-Synthetic Fiber Reinforced Concrete: Experimental and Numerical Investigation

“…The incorporation of fibers in cement-based composites allows the partial or even total substitution of traditional reinforcement (reinforcing steel bars) with a positive effect on the fracture energy of the matrix [ 7 ], cracking control [ 8 , 9 , 10 , 11 , 12 ], fire resistance [ 13 , 14 , 15 ], fatigue [ 16 , 17 ], redistribution capacity [ 18 , 19 , 20 , 21 ], and impact resistance [ 22 , 23 , 24 , 25 ]. As a result, the application of FRC is already observed in a multitude of structural elements, such as precast tunnel segments [ 26 , 27 , 28 ], elevated flat slabs [ 29 , 30 , 31 ], reinforced earth-retaining walls [ 32 ], and ground-supported flat slabs for industrial applications [ 33 , 34 ].…”

A unified approach for determining the strength of Frc members subjected to torsion—Part I: Experimental investigation

“…It is well accepted that the use of randomly orientated and uniformly distributed steel fibers within concrete significantly improves the post-cracking behavior of concrete. [2][3][4][5] Several experimental and analytical campaigns over the last few decades have clearly demonstrated the effectiveness of fibers in resisting shear [6][7][8][9][10] and flexure [11][12][13][14][15][16][17] in large scale structural elements. Recent studies have also demonstrated that the inclusion of fibers can also significantly improve the serviceability behavior of concrete structures.…”