Issue 29

R. Serpieri et alii, Frattura ed Integrità Strutturale, 29 (2014) 284-292; DOI: 10.3221/IGF-ESIS.29.24 284 Focussed on: Computational Mechanics and Mechanics of Materials in Italy Bond-slip analysis via a cohesive-zone model simulating damage, friction and interlocking R. Serpieri, L. Varricchio Dipartimento di Ingegneria, Università degli Studi del Sannio, Benevento, Italy rserpier@unisannio.it , luigi.varricchio@ingpec.eu E. Sacco Dipartimento di Ingegneria Civile e Meccanica, Cassino, Università di Cassino e del Lazio Meridionale, (FR), Italy sacco@unicas.it G. Alfano School of Engineering and Design, Brunel University, Uxbridge, UK giulio.alfano@brunel.ac.uk A BSTRACT . A recently proposed cohesive-zone model which effectively combines damage, friction and mechanical interlocking has been revisited and further validated by numerically simulating the pull-out test, from a concrete block, of a ribbed steel bar in the post-yield deformation range. The simulated response is in good agreement with experimental measurements of the bond slip characteristics in the post-yield range of deformed bars reported in the literature. This study highlights the main features of the model: with physically justified and relatively simple arguments, and within the sound framework of thermodynamics with internal variables, the model effectively separates the three main sources of energy dissipation, i.e. loss of adhesion, friction along flat interfaces and mechanical interlocking. This study provides further evidence that the proposed approach allows easier and physically clearer procedures for the determination of the model parameters of such three elementary mechanical behaviours, and makes possible their interpretation and measurement as separate material property, as a viable alternative to lumping these parameters into single values of the fracture energy. In particular, the proposed approach allows to consider a single value of the adhesion energy for modes I and II. K EYWORDS . Fracture energy; Friction; Interlocking; Thermodynamics with Internal Variables; Interface Elements; Mixed-mode Delamination. I NTRODUCTION ohesive ‐ zone models (CZMs) are widely used to simulate initiation and propagation of cracks along structural interfaces. They represent an effective alternative approach to fracture-mechanics-based methods for a wide variety of problems at very different scales, such as crack growth in dams, mortar-joint failure in brick masonry, bond-slip response of reinforcing bars in concrete, debonding of adhesive joints, delamination or fibre ‐ matrix debonding in composites, among many others. Many of such problems entail combination of de-cohesion and frictional sliding, C