tesi A. Caggiano.pdf - EleA@UniSA - Università degli Studi di Salerno

Chapter 8. Elasto-plastic microplane formulation for FRCCgration points at the unit hemisphere, is investigated in the case of simple shear. Forthis purpose, the same material parameters as in the tension problems of previoussubsection are considered. Thus, 2, 4, 6, 8, 21 and 25 integration points (on the unithemisphere) are considered for the numerical analyses. The result can be found inFigure 8.11 and 8.12, where the lateral load vs. displacement curves are plotted. Particularly,Figure 8.11 emphasizes the comparative response of three kinds of concrete:• plain concrete,• FRC with steel fibers characterized by fiber contents of 2.0% and• FRC with 5.0% of steel fibers.The figure clearly highlights the clear phenomenological effect of fibers when addedon cementitious matrix. Fiber inclusions mainly enhance the mechanical property ofSFRC in terms of both shear strength and ductility. Then, Figure 8.12 highlights thedifference in responses when a different number of integration points are considered.It can be stated that an acceptable accuracy involves at least 21 points of integration,also demonstrated on the work by Bazant and Oh [1986]. A poor approximation, whichtakes place for integrations in which a number of considered points is lower than 21,can be observed around the peak strength and in the post-peak regime.8.7 Closing remarksA microplane-based plasticity approach, aimed at simulating the failure behavior ofFiber Reinforced Cementitious Composite (FRCC), has been presented in this chapter.It has been founded on the macroscopic smeared-crack approach considering thefailure of FRCC in a continuum point of view. The constitutive model considers the wellknown“Mixture Theory” to simulate the combined bridging interactions of fibers inconcrete cracks. The interactions between steel fibers and concrete matrix, associatedwith bond-slip and dowel mechanisms respectively, have explicitly been accountedin the constitutive formulation. The numerical simulations demonstrate that theconstitutive proposal mainly captured the fundamental behaviors of FRCC. Very goodagreement between numerical results against experimental data, available in scientificliterature, have been achieved in terms of peak-strength and post-cracking toughness.172