Evaluation of flexural fracture toughness for quasi-brittle structural materials using a simple test method

Xiao, X; Taha, M M. Reda; Yi, J; Shrive, N G
August 2002
Canadian Journal of Civil Engineering;Aug2002, Vol. 29 Issue 4, p567
Academic Journal
As new structural concepts such as partial prestressing and steel-free bridge decks are more widely accepted and used, there is an increasing need for a reliable and reproducible fracture performance criterion that can describe resistance to crack growth. The required criterion should also be easy to determine experimentally so that it can be incorporated in structural specifications. The nonlinear behaviour of concrete and masonry materials suggested that quasi-brittle fracture mechanics approaches may be the most suitable for determining their fracture performance. The effective elastic crack model originally developed by Karihaloo and Nallathambi (1989) was modified to evaluate the critical crack depth under pure flexural stresses. A computer program was developed to calculate this depth iteratively from the experimental results. An experimental programme examining the fracture performance of four different structural materials (high performance concrete, mortar, fibre reinforced concrete, and masonry units) was carried out to examine the applicability of the model. As no post-peak data are required for the analysis, the model allows the use of a simple test setup to evaluate the fracture performance of quasi-brittle materials experimentally.Key words: fracture toughness, linear elastic fracture mechanics (LEFM), elastoplastic fracture mechanics (EPFM), quasi-brittle fracture mechanics, effective elastic crack, high performance concrete, masonry, fibre reinforced concrete.Car nouveau des concepts structuraux tels que la précontrainte partielle et les paquets acier-libres de passerelle sont reçus et plus largement répandus, il y a un besoin croissant de critère fiable et reproductible d'exécution de rupture qui peut décrire la résistance à la progression de la fissure. Il devrait également être facile déterminer le critère exigé expérimentalement de sorte qu'il puisse être incorporé dans des caractéristiques structurales. Le comportement non linéaire des matériaux de béton et de maçonnerie a suggéré que les approches de mécanique de rupture quasi-fragile puissent être les plus appropriées à déterminer leur exécution de rupture. Le modèle élastique pertinent de fente initialement développé par Karihaloo et Nallathambi (1989) a été modifié pour évaluer la profondeur critique de fente sous des efforts flexural purs. Un programme machine a été développé pour calculer cette profondeur itérativement à partir des résultats expérimentaux. Un programme expérimental examinant l'exécution de rupture de quatre matériaux structuraux différents (le béton de rendement élevé, le mortier, fibre a renforcé le béton et les unités de maçonnerie) a été effectué pour examiner l'applicabilité du modèle. Car on n'a besoinavoir besoin d'aucun poteau-crête pour l'analyse, le modèle permet l'utilisation d'une installation d'essai simple d'évaluer l'exécution de rupture des matériaux quasi-fragiles expérimentalement.Mots clés : rompez la dureté, LEFM, EPFM, mécanique de rupture de quasi-brittle, la fente élastique pertinente, le béton de rendement élevé, maçonnerie, le béton renforcé de fibres.


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