Issue 31

A. Abrishambaf et alii, Frattura ed Integrità Strutturale, 31 (2015) 38-53; DOI: 10.3221/IGF-ESIS.31.04 45 (a) (b) Figure 9 : Predicted orientation profile: (a) θ= 0 ° and (b) θ= 90 ° . 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 Exponential tendency R-square=0.90 N f [-] N f eff [-] Figure 10 : Number of the fibres, f N , versus number of the effective fibres, f eff N . N UMERICAL SIMULATION he most suited test to derive the mode I fracture parameters is the uniaxial tensile test. However, the latter test involves some difficulties such as: the necessity of specialized and expensive equipment; sophisticated test set-up to avoid detrimental interferences, like load eccentricity, since it decreases the stress at the onset of crack initiation [22]. On the other hand the splitting tensile test could be considered as an alternative option for this purpose, because it is cheaper, less sophisticated testing equipment is needed, and can be executed on both cubes and extracted cores. In this section a methodology to predict the stress – crack width ( σ – w ) relationship of SFRSCC using an inverse analysis, IA, procedure based on the results of the splitting tensile test will be presented and discussed. For this purpose, numerical simulations of the splitting tensile tests were carried out with a nonlinear 3 D finite element model. In order to confirm the accuracy of the proposed methodology, the σ – w response obtained through the IA of the splitting test results was compared to the σ – w response obtained from the uniaxial tensile test. Modelling and simulation The average experimental force – crack width responses of the splitting tensile tests (Fig. 4) were simulated using ABAQUS ® finite element software [23]. Eight-node hexahedral shape solid elements with 8-integration points were used. The concrete damage plasticity model was implemented in order to simulate mechanical properties of concrete [24, 25]. Because of the symmetry in the specimen geometry, supports and test loading applied in the splitting tensile test, only a quarter of the core was simulated, see Fig. 11(a). Since the specimen had distinct thicknesses it consists of two main parts namely: Notch and Un-notch (flush). After meshing each part individually, the assembled mesh is shown in Fig. 11(b) with a total number of 5674 elements. Similar to the performed in the experimental procedure, in the numerical simulation a prescribed displacement was applied on top of the notch. T