Title:
RC Beams with Steel Fibres - Towards Better Determination of their Minimum Conventional Reinforcement Ratio
Author(s):
Dancygier, A.N.; Karinski, Y.S.
Publication:
Symposium Paper
Volume:
343
Issue:
Appears on pages(s):
246-253
Keywords:
Cracking localization; Fibre-reinforced concrete; Flexural ductility; Minimum reinforcement ratio
DOI:
Date:
10/1/2020
Abstract:
Minimum longitudinal reinforcement ratio in reinforced concrete (RC) beams is determined by criteria that refer to flexural capacity. However, relatively recent experiments have shown that RC beams with steel fibres (RFRC beams) with the above-determined minimum reinforcement, exhibit a pronounced reduction in their flexural ductility, compared with similar plain RC beams. This phenomenon was characterized by cracking localization, when only one or two cracks widened significantly more than the other cracks did. This led to increase of the steel plastic strains, even up to its rupture, in the rebars that crossed these cracks. The ductility
reduction in this case impairs the structural response of RFRC beams compared with RC beams without fibres. Therefore, this effect of the fibres must also be considered when determining
the minimum longitudinal reinforcement ratio in RFRC beams.
The paper presents analysis of test results that pertain to flexural ductility in RFRC beams and its relation with the cracking localization phenomenon. This phenomenon may be quantified by the ratio between the number of the significantly wide cracks and the total number of flexural cracks. It is shown that RFRC beams with smaller reinforcement ratios had higher cracking localization. It is also shown that as the reinforcement ratio decreases below a certain
value, which is considerably larger than the minimum required by the codes, the flexural ductility decreases as well. Within this range of small reinforcement ratio, these two trends are related, whereas for larger reinforcement ratios, there is no effect of cracking localization on the flexural ductility.
Related References:
Bentur A, Mindess S (2007). Fibre reinforced cementitious composites, 2nd edition. New York: Taylor & Francis.
CEN (2007). EN 14651:2005+A1:2007. Test method for metallic fibre concrete – Measuring the flexural tensile strength (limit of proportionality (LOP), residual).
Dancygier AN, Savir Z (2006). Flexural behavior of HSFRC with low reinforcement ratios. Eng Str; 28(11): 1503-1512.
Dancygier AN, Karinski YS (2014). Probabilistic model of the cracking localization in axially loaded fibrous reinforced concrete bars. Eng Str; 79: 417-426.
Dancygier AN, Berkover E (2016). Cracking localization and reduced ductility of fiberreinforced concrete beams with low reinforcement ratios. Eng Str; 111: 411-424.
Dancygier AN, Karinski YS, Navon Z (2017). Cracking localization in tensile conventionally reinforced fibrous concrete bars. Const Build Mat, 149: 53-6
Deluce JR, Vecchio FJ (2013). Cracking behavior of steel fiber-reinforced concrete members containing conventional reinforcement. ACI Struct J; 110(3): 481-490.
di Prisco M, Colombo M, Dozio D (2013). Fibre-reinforced concrete in fib model code 2010: Principles, Models and Test Validation. Struct Concr; 14(4): 342–361.
fib, International Federation for Structural Concrete, SAG 5 (2013). Model Code for concrete structures 2010. Wilhelm Ernst & Shon.
Park R (1989). Evaluation of ductility of structures and structural assemblages from laboratory testing. Bulletin of The New Zealand National Society for Earthquake Engineering; 22:
155-166.
Park A, Paulay T (1975). Reinforced concrete structures. John Wailey & Sons.
Redaelli D, Muttoni A (2007). Tensile behaviour of reinforced ultra-high performance fiber reinforced concrete element. Proc fib Symposium: Concrete structures: stimulators of
development. Dubrovnik, Croatia.
Schumacher P, Walraven JC, den Uijl JA, Bigaj-van Vliet A (2009). Rotation capacity of selfcompacting steel fibre reinforced concrete beams. HERON; 54: 127-161.
Vandewalle L (2000). Cracking behaviour of concrete beams reinforced with a combination of ordinary reinforcement and steel fibers. Mat and Struct; 33: 164-70.
Yoo DY, Yoon YS (2015). Structural performance of ultra-high-performance concrete beams with different steel fibers. Eng Str; 102: 409–423.