Cracking Analysis of FRC Beams under Sustained Long-Term Loading

Abstract:

Crack formation within concrete members undergoing flexural loading is a complex mechanism, which governs the serviceability and durability of concrete structures. As for reinforced concrete (RC) members, a number of works based on empirical or theoretical approaches are published in the scientific literature. All the models propose a formulation for the estimation of crack spacing and crack width taking into account several parameters. Mechanical properties of concrete matrix, reinforcement ratio, concrete cover, bar diameter and size effect are the most influencing parameters on the cracking pattern of RC members, while tension stiffening can be influential as well. In Fiber Reinforced Concrete (FRC) elements the presence of short fibers modifies the crack pattern within the members due to the development of a residual tensile stress and greater toughness. Normally the number of cracks within the length of FRC members is higher while the mean crack spacing and the crack width are lower. In fact the crack bridging effect of fibers consists in post-cracking stresses between the crack faces. Such mechanism is mainly governed by the interface bond between fiber and concrete matrix. Therefore, the volume fraction and the geometrical properties of fibers strongly influence the overall contribution in the cracking phenomena. A limited number of design codes have taken into account the modified behaviour of FRC members (especially in the case of steel fibers) by providing specific equations for crack width. This work presents the results of an experimental campaign on RC beams subjected to sustained service loads and environmental exposure for 72 months. In some beams, short steel or polyester fibers were added to the concrete matrix. The results presented in the paper show that the addition of fibres in concrete reduces both flexural displacements and crack widths, by modifying also the long-term behaviour of FRC members.

• Periodical: Key Engineering Materials (Volume 711)
• Pages: 844-851
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.711.844
• Online since: September 2016
• Authors: Leandro Candido*, Francesco Micelli, Emilia Vasanelli, Maria Antonietta Aiello, Giovanni A. Plizzari
• Keywords: Crack Width, FRC Beams, Long-Term Loading

References

[1] M. Di Prisco, G. Plizzari, L. Vandewalle, Fibre reinforced concrete: new design perspectives, Mater. Struct. 42 (2009) 1261–1281.

DOI: 10.1617/s11527-009-9529-4

[2] Norme tecniche per le costruzioni, D.M. 14/01/2008. (2008).

[3] FIB Model Code, First complete draft, vol 2, chaps (7–10) in fib Bulletin 562010, ISBN 978-2-88394-096-3. (2010).

[4] K.H. Tan, P. Paramasivam and K.C. Tan, Cracking characteristics of reinforced steel fiber concrete beams under short and long-term loadings, Adv. Cem. Based Mat., 2 (1995) 127-137.

DOI: 10.1016/1065-7355(95)90013-6

[5] S.A. Altoubat and D.A. Lange, A new look at tensile creep of fiber reinforced concrete, ACI Special Publication 216 (2003) 143–160.

[6] E. Vasanelli, F. Micelli, M.A. Aiello and G. Plizzari, Long term behaviour of FRC flexural beams under sustained load, Eng. Struct., 56 (2013) 1858-1867.

DOI: 10.1016/j.engstruct.2013.07.035

[7] E. Vasanelli, F. Micelli, M.A. Aiello and G. Plizzari, Crack width prediction of FRC beams in short and long term bending condition, Mat. and Structures 47 1-2 (2014) 39-54.

DOI: 10.1617/s11527-013-0043-3

[8] L. Vandewalle, RILEM TECHNICAL COMMITTEES - Recommendations of RILEM TC 162-TDF: Test and design methods for steel fibre reinforced concrete, Mat. and struct., 33(225) (2000) 3-5.

DOI: 10.1617/13628

[9] UNI EN ISO 15630-1, Steel for the reinforcement and pre-stressing of concrete - Test methods - Part 1: Reinforcing bars, wire rod and wire, Italian Board of Standardization (UNI).

DOI: 10.3403/02593598

[10] E. Vasanelli, F. Micelli, M.A. Aiello and G. Plizzari, Mechanical characterization of fiber reinforced concrete with steel and polyester fiber, Proc. of the BEFIB 2008, 7th RILEM Int. Symp. on Fibre Reinforced Concrete, Chennai India (2008).

DOI: 10.1007/978-3-030-83719-8_47

[11] UNI EN 196-1, Cement - Part 1: Composition, specifications and conformity criteria for common cements, Italian Board of Standardization (UNI) (2007).

[12] ACI Committee 544, Measurement of Properties of Fiber Reinforced Concrete, ACI Report 544. 2R-89, American Concrete Institute, Farmington Hillis.

[13] Eurocode 2, Design of concrete structures - Part 1-1: General rules and rules for buildings, EN 1992-1-1: 2004 (2004).

[14] UNI EN 206-1, Concrete - Specification, performance, production and conformity, Italian Board of Standardization (UNI), 2001 (2010).

[15] L. Candido, F. Micelli, E. Vasanelli, M.A. Aiello, and G. Plizzari, Cracking behaviour of FRC beams under Long-term loading, CONCREEP 10 (2015) 1147-1156.

DOI: 10.1061/9780784479346.137