Issue 29

S. de Miranda et alii, Frattura ed Integrità Strutturale, 29 (2014) 293-301; DOI: 10.3221/IGF-ESIS.29.25 293 Focussed on: Computational Mechanics and Mechanics of Materials in Italy A simple beam model to analyse the durability of adhesively bonded tile floorings in presence of shrinkage S. de Miranda, A. Palermo, F. Ubertini University of Bologna stefano.demiranda@unibo.it , antonio.palermo6@unibo.it , francesco.ubertini@unibo.it A BSTRACT . A simple beam model for the evaluation of tile debonding due to substrate shrinkage is presented. The tile-adhesive-substrate package is modeled as an Euler-Bernoulli beam laying on a two-layer elastic foundation. An effective discrete model for inter-tile grouting is introduced with the aim of modelling workmanship defects due to partial filled groutings. The model is validated using the results of a 2D FE model. Different defect configurations and adhesive typologies are analysed, focusing the attention on the prediction of normal stresses in the adhesive layer under the assumption of Mode I failure of the adhesive. K EYWORDS . Tile flooring; Tile debonding; Adhesive joint; Elastic foundation. I NTRODUCTION ile floorings are extensively used in residential and industrial buildings. A typical tiled floor consists of an upper layer of tiles separated by grouting interfaces and attached via an adhesive stratum to a lower cementitious substrate (Fig. 1). Although tile floorings guarantee high resistance and durability also in severe exposure conditions, they are prone to suffer from debonding failure, typically induced by differential elongation/shortening between tile layer and substrate. The differential deformation may be caused by substrate shrinkage, either due to thermal gradients or residual maturation of cementitious substrate. Substrate shrinkage determines an eccentric compression in the tiles transferred by a shear mechanism through the adhesive layer. The inherent eccentricity of compression due to the geometric configuration of the tiled floor, eventually increased by the presence of grouting defects due to poor workmanship, may induce tile debonding due to Mode I failure of the adhesive layer. Nowadays several types of adhesives are available in the market with increasing performance in terms of strength and deformation capacities at the prize of increasing costs. Therefore, for a cost-effective design of the tile flooring systems it is of fundamental importance an assessment of the stress state of the adhesive layer induced by the differential deformations. In recent years, the extensive use of adhesive layers and adhesive lap joints in different engineering applications has driven the attention of several researches. Different studies have been carried out by modelling the adhesive layer as a fracturing interface. Analytical models have been developed to describe the interface decohesion in laminated beams and simulate peeling tests [1]. Finite element models have been widely used to simulate the debonding of adhesive lap joints (see e.g. [2,3]). Mahaboonpachai et al. [4] investigated the debonding of tiles in external wall claddings by formulating a two dimensional cohesive interface element. Lignola et al [5]. developed a refined Finite Element Model to analyse the stress and strain distributions in a tile-adhesive-substrate subjected to substrate shrinkage. The same problem has been studied T

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