The use of steel fiber reinforced concrete (SFRC hereafter) is becoming more and more
common. Building codes and recommendations are gradually including the positive effect of
fibers on mechanical properties of concrete. How to take advantage of the higher ductility
and energy absorption capacity of SFRC to reduce anchorage lengths when using fibers is
not a straightforward issue.
Fibers improve bond performance because they confine reinforcement (playing a similar
role to that of transverse reinforcement). Their impact on bond performance of concrete is
really important in terms of toughness/ductility.
The study of previous literature has revealed important points of ongoing discussion
regarding different issues, especially the following: a) whether the effect of fibers on bond
strength is negligible or not, b) whether the effect of fibers on bond strength is dependent
on any other factors such as concrete compressive strength or concrete cover, c)
quantifying the effect of fibers on the ductility of bond failure (bond toughness). These
issues have defined the objectives of this thesis.
A modified version of the Pull Out Test (POT hereafter) has been selected as the most
appropriate test for the purposes of this research. The effect of a number of factors on bond
stress¿slip curves has been analyzed. The factors considered are: concrete compressive
strength (between 30 MPa and 50 MPa), rebar diameter (between 8 mm and 20 mm),
concrete cover (between 30 mm and 5 times rebar diameter), fiber content (up to 70
kg/m3), and fiber slenderness and length.
The experimental program has been designed relying on the principles of statistical Design
Of Experiments. This has allowed to select a reduced number of combinations to be tested
without any bias or loss of accuracy. A total of 81 POT specimens have been produced and
tested.
An accurate model for predicting the mode of bond failure has been developed. It relates
splitting probability to the factors considered. It has been proved that increasing fiber
content restrains the risk of splitting failure. The favorable effect of fibers when preventing
splitting failures has been revealed to be more important for higher concrete compressive
strength values. Higher compressive strength values require higher concrete
cover/diameter ratios for splitting failure to be prevented. Fiber slenderness and fiber
length modify the effect of fiber content on splitting probability and therefore on minimum
cover/diameter ratios required to prevent splitting failures. Two charts have been
developed for estimating the minimum cover/ diameter ratio required to prevent splitting.
Predictive equations have been obtained for estimating bond strength and areas under the
bond stress¿slip curve as a function of the factors considered. Increasing fiber content has a
slightly positive impact on bond strength, which is mainly determined by concrete
compressive strength. On the contrary, fibers have a very important effect on the ductility of
bond failure, just as well as concrete cover, as long as no splitting occurs.
Multivariate analysis has proved that bond stress corresponding to the onset of slippage
behaves independently from the rest of the bond stress¿slip curve. The effect of fibers and
concrete compressive strength on bond stress values corresponding to the onset of slips is
mainly attributable to their influence on the material mechanical properties. On the
contrary, the effect of fibers and concrete cover on the rest of the bond stress¿slip curve is
due to their structural role. / García Taengua, EJ. (2013). Bond of Reinforcing Bars to Steel Fiber Reinforced Concrete (SFRC) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/32952
| Identifer | oai:union.ndltd.org:upv.es/oai:riunet.upv.es:10251/32952 |
| Date | 21 October 2013 |
| Creators | García Taengua, Emilio José |
| Contributors | Martí Vargas, José Rocío, Serna Ros, Pedro, Universitat Politècnica de València. Departamento de Ingeniería de la Construcción y de Proyectos de Ingeniería Civil - Departament d'Enginyeria de la Construcció i de Projectes d'Enginyeria Civil |
| Publisher | Universitat Politècnica de València |
| Source Sets | Universitat Politècnica de València |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/acceptedVersion |
| Source | Riunet |
| Rights | http://rightsstatements.org/vocab/InC/1.0/, info:eu-repo/semantics/openAccess |
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