A METHOD OF STUDYING THE EFFECT OF VIBRATORY STRESS, INCLUDING FATIGUE, ON CONCRETE IN FLEXURE
THE METHOD AND APPARATUS ENABLE VIBRATORY FLEXURAL STRESSES OF MAGNITUDES COMPARABLE WITH THOSE USED IN CONVENTIONAL QUASI-STATIC TESTS TO BE APPLIED TO CONCRETE BEAMS. THE BEAM IS MOUNTED HORIZONTALLY ON RIGID SUPPORTS AND IS VIBRATED IN FLEXURE BY A MOVING-COIL VIBRATOR COUPLED TO THE UPPER FACE OF THE BEAM AT THE CENTRE. THE FREQUENCY OF RESONANCE AND THE STRAIN IN THE BEAM AT THE CENTRE OF THE TOP FACE ARE MEASURED AND, IN NORMAL OPERATION, THE DRIVING CURRENT IS ADJUSTED TO MAINTAIN A CONSTANT VALUE OF STRAIN WHILST CHANGES OF FREQUENCY WITH TIME ARE OBSERVED. A DECREASE IN FREQUENCY INDICATES A DECREASE IN THE DYNAMIC YOUNGS MODULUS OF ELASTICITY OF THE CONCRETE, AND IS ASSOCIATED WITH A DEVELOPMENT OF MICRO-CRACKS IN THE CONCRETE. THE CRACKS WHICH FORM AT SUFFICIENTLY HIGH LEVELS OF STRAIN FATIGUE HAVE BEEN OBSERVED BY A PHOTO-ELASTIC TECHNIQUE BEFORE THE APPEARANCE OF VISIBLE CRACKS. STRAINS BETWEEN 60 AND 120 PARTS PER MILLION ULTIMATELY LED TO FATIGUE OF THE CONCRETES TESTED. STRESS-STRAIN RELATIONSHIPS WERE DERIVED FROM CURVES RELATING RESONANT FREQUENCY WITH MAGNITUDE OF STRAIN, AND WERE FOUND TO BE APPROXIMATELY LINEAR FOR UN-FATIGUED SPECIMENS AND MARKEDLY NON-LINEAR FOR SPECIMENS WHICH HAD BECOME FATIGUED.
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Supplemental Notes:
- Vol17, No53, PP211-216, 6FIG, 2TAB, 3REF
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Authors:
- Gatfield, E N
- Publication Date: 1965-12
Media Info
- Serial:
Subject/Index Terms
- TRT Terms: Beams; Concrete; Cracking; Equipment; Fatigue (Physiological condition); Flexure; Measurement; Methodology; Modulus of elasticity; Photoelasticity; Resonance; Strain (Mechanics); Stresses; Studies; Vibration
- Uncontrolled Terms: Concrete beams
- Old TRIS Terms: Photoelastic method; Strains
- Subject Areas: Highways; Materials;
Filing Info
- Accession Number: 00212224
- Record Type: Publication
- Source Agency: Road Research Laboratory /UK
- Files: TRIS
- Created Date: May 1 1994 12:00AM