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

3 Zero-thickness interface model forFRCCThis chapter deals with the formulation of a zero-thickness interface model conceivedwithin the general framework of the discrete-crack approach and aimed at simulatingthe mechanical response of Fiber-Reinforced Cementitious Composites (FRCCs).Following a cohesive-frictional interface proposal, already available in scientific literaturefor plain concrete, the formulation of an interface constitutive model is furtherdeveloped and extended to capture the key mechanical phenomena controlling theFRCC behavior. An original approach is introduced for reproducing the complex influenceof fibers on cracking phenomena of concrete/mortar matrix. Particularly, theinterface model takes into account both the bond-slip strength and dowel mechanismsgenerated by fibers crossing the concrete cracks.This novel interface model for FRCC is mainly based on the flow Theory of Plasticity andFracture Mechanics concepts to control the energy release during cracking processesunder both mode I and/or II of fracture. The constitutive law represents an extensionof the previous interface formulation for plain concrete approached by Carol et al.[1997] and by Lopez et al. [2008a,b] to take into account the interaction betweencement/mortar and steel fibers. The well-known “Mixture Theory” is adopted formodeling the interactions between fibers and the surrounding cementitious composite.In this chapter, section 3.1 briefly reports the main issues of the interface model forFRCC and outlines the key assumptions utilized in the constitutive proposal. Section3.2 summarizes an overview of “Mixture Theory” concepts [Trusdell and Toupin, 1960]and its use on the given discontinuous proposal. The interface model, aimed in principleat reproducing the post-peak softening behavior due to crack propagations inplain concrete is outlined in section 3.3. It is formulated by means of an incrementalapproach, which is similar to the one usually adopted in the classical flow theory of43