STUDY OF CRACK PROPAGATION IN UNREINFORCED CONCRETE

ETUDE DE LA PROPAGATION D'UNE FISSURE DANS UN BETON NON ARME

THE PRINCIPLE OF THIS TEST IS CONVENTIONAL: THE TEST SPECIMEN IS A DOUBLE CANTILEVERED BEAM (DCB); THE FORCE TENDING TO PULL APART THE TWO CANTILEVERS IS USED TO KEEP THE RATE OF OPENING OF THE CRACK CONSTANT. THE ORIGINALITY OF THE TEST LIES IN THE DIMENSION OF THE BEAM, WHICH ENABLES CRACK PROPAGATION TO BE STUDIED OVER A GREAT LENGTH (1,80 M). LONGITUDINAL PRESTRESSING FORCE PREVENTS THE CRACK FROM DEVIATING. THE VISIBLE CRACK IS OBSERVED WITH A MAGNIFYING GLASS, AND CLOSE ATTENTION IS PAID TO THE OBSERVATION OF THE BEHAVIOUR OF THE NON-ELASTIC ZONE AT THE BOTTOM OF THE CRACK. TWO METHODS ARE USED: PHOTO-ELASTIC LACQUER AND LOCALIZED SOUND WAVES. THIS SHOWS THE MAGNITUDE OF THE DISTURBED NON-ELASTIC ZONE (APPROXIMATELY 20 CM). THE LARGE SIZE OF THE SPECIMEN ENABLES PRACTICAL RESULTS TO BE REACHED: DURING INITIAL PROPAGATION FAILURE ENERGY INCREASES AS THE CRACK PROPAGATES; A STEADY VALUE OF ULTIMATE ENERGY IS ONLY REACHED AFTER 50 CM OF CRACK PROPAGATION; THIS STEADY VALUE IS TEN TIMES AS GREAT AS THE INITIAL VALUE. IT IS PROBABLE THAT MOST OF THE RESULTS GIVEN IN THE EXISTING LITERATURE AND OBTAINED ON SAMPLES THAT ARE TOO SMALL, UNDERESTIMATE THE RESISTANCE OF UNREINFORCED CONCRETE TO CRACK PROPAGATION.

Language

  • French

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Filing Info

  • Accession Number: 01295369
  • Record Type: Publication
  • Source Agency: Institut Francais des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)
  • Files: ITRD
  • Created Date: Nov 21 2010 5:00AM