SF+RC Modelling using DIANA FEA

A van den Bos, S Dhanmehere (DIANA FEA); Y Dai (TU Delft)


The design of structural members utilising steel fibre + reinforced concrete (SF+RC) is gaining popularity. SF+RC implies enhancing normal designed reinforced concrete by adding fibre content, thereby making it more robust. Usually, this enhancement enables reduction in size of concrete sections and/or the amount of traditional reinforcement.

The modelling of the material is often based on a smeared crack approach. In DIANA this is already possible for a long time using a total strain crack model. Since a few years, an official tensile curve named FRCCON has been available. The softening behaviour of the concrete combined with the steel fibres can be input as a stress-CMOD or stress-strain relation. Several papers on this material have already been published, Bos, A.A. van den et.Al. (2015), K. Younis et.Al. (2014), Bos, A.A. van den, et.Al. (2016) The parameters of this tensile curve are obtained either from the Model Code 2010 and/or via tests done on small bending prisms. This could be a 3-point notched beam test or a 4-point bending test. Via inverse modelling, one can obtain the parameters for material input.

Many different types of fibres exist, which can be added in different dosages and combined with concrete to produce SF+RC. In order to standardise design procedures, it is of interest to have an idea about the combined behaviour of a particular fibre-type added to concrete in a particular dosage. However, since the number of possible combinations are very large and test results are valid only for a certain combination of volumes, the inputs for a new combination in structural design can be difficult to identify. This paper aims at developing a strategy to numerically calculate the response of SFRC such that the effect of different fibre-dosages and fibre-types can be considered within a single model.

For the application it is important to describe the influence of the different parameters on the ultimate strength of the structural member. The main influencing parameters are investigated and described. This will be the concrete strength, the shear along the fibre, the stiffness and strength of the end anchors and the orientation and distribution factors.

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