Steel Fibres in Reinforced Concrete Structures of Complex Shapes: Structural Behaviour and Design Perspectives
Doctoral thesis, 2014
In concrete structures of complex geometries, the formability of concrete is an asset.
However, complex geometries introduce time-demanding form and reinforcement works.
By streamlining design and production, utilising the benefits of computational tools as well
as modern production technologies, the buildability of complex concrete structures can
be increased. Combinined with the use of alternative reinforcement methods, the scope
of unique concrete structures could be broadened. Conventionally, steel bars have been
used; however, alternative reinforcement methods have been introduced. First, several
reinforcement methods were studied and the focus for the remainder of the work were
set on the structural behaviour of conventional reinforcement and steel fibre reinforced
It may not be possible to apply standard idealisations to concrete structures of complex
geometry. Two methods for the design of conventional reinforcement, based on linear
finite element analyses, were investigated and both were found to provide a rational
approach calculating the amount of reinforcement needed.
To investigate the structural behaviour of SFRC, an experimental programme was conducted.
Two-way slabs with combinations of conventional reinforcement and SFRC
were tested, investigating the effect from steel fibres on load redistribution. To provoke
redistribution after cracking, the conventional reinforcement was arranged asymmetrically,
forming a weak and a strong direction. As expected, steel fibres increased the load-carrying
capacity and the number of cracks. Furthermore, the steel fibres increased the portion of
applied load transferred to the supports in the weak direction and contributed to evening
out the load of the length of the support. Material characterisation of the SFRC was
performed through both uni-axial and three-point bending tests. A numerical approach
was successfully utilised to relate the two test methods to each other.
Analytical and numerical analyses of both beams and slabs were conducted, and the results
were compared with experiments. In these cases, the additional capacity provided by the
steel fibres was observed both experimentally and in numerical analysis. Depending on
the interpretation of analytical proposal in Model Code 2010, the load-carrying capacity
was either underestimated or rather accurately estimated.
Through a combination of experimental, numerical and analytical work on both structural
and material levels, this thesis contributes to an improved understanding for the structural
use of SFRC, especially in structures of complex geometry.
Keywords: Concrete structres, Geometrically complex structures, Reinforcement alternatives,
Steel fibre reinforcement, Rational design
Geometrically complex structures
Steel fibre reinforcement