Purpose fig 4 eccentricity is shown in note sometimes

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Unformatted text preview: IAGRAMMATIC VIEW OF APPARATUS FOR FLEXURE TEST OF CONCRETE BY THIRDPOOINT LOADING METHOD C-2.2 Apparatus for making flexure tests of concrete should be designed to incorporate the following principles: a) The distance between supports and points of load application should remain constant for a given apparatus; b) The load should be applied normal to the loaded surface of the beam and in such a manner as to avoid eccentricity of loading; c) The direction of the reactions shdd be parallel to the direction of the applied load at all times during the test; d) The load should bc aeplied at a uniform rate and in such a manner IS to avtiid shock; and e) The ratio of distance between point of load application and nearest reaction to the depth of the beam should be not less than one, 42 IS : 457 - 1957 C-2.2.1 The directions of loads and reactions may be maintained parallel by judicious use of linkages, rocker bearings, and flexure plates. Eccentricity of loading can be avoided by use of spherical or roller bearings. C-3. TEST SPECIMEN C-3.1 The test specimen times its depth as tested. C-4. shall have a span as nearly as practicable three PROCEDURE C-4.1 The test specimen shall be turned on its side with respect to its The load-applying position as moulded and centred on the bearing blocks. blocks shall be brought in contact with the upper surface at the third point If full contact is not obtained between the specibetween the supports. men and the load-applying blocks and the supports, due to the surfaces of the specimen being out of plane, the surfaces of the specimen where they are in contact with the blocks or supports shall be capped to meet The load may be the requirements given in Appendix E of*IS: 456-1957. applied rapidly up to approximately 50 percent of the breaking load, after which it shall be applied at such a rate that the increase in extreme fibre stress does not exceed 10 kg per sq cm ( or 150 lb per sq in ) per minute. c-5. MEASUREMENT OF SPECIMENS AFTER TEST ES.1 Measurements to the nearest 0.25 cm ( or O-1 in ) shall be made to determine the average width and average depth of the specimen at the section of failure. C-6. CALCULATIONS C-6.1 If the fracture occurs within the middle third of the span length, the modulus of rupture shall be calculated as follows: R= PC bd’ where P = modulus of rupture in kg per sq cm square inch ), R = maximum applied load indicated by the in kg (or lb), c = span length in cm ( or in ), b = average width of specimen in cm ( or in d = average depth of specimen in cm ( or in ( or pounds testing machine ), and ). Non - Weight of the bram ir not included in the above calculation. *Second revbfoa fu1964. 43 per 1s : 457 - 1957 C-6.2 If the fracture occurs outside the middle third of the span length by not more than 5 percent of the span length, the modulus of rupture shall be calculated as follows: R- ?!?_ bd’ where a = distance between line of fracture and the nearest support measured along the ccntrc line of the bottom surface of the he:m in cm ( or in.) :LIH~other symbols have the same significance as given urltlcr C-6.1. C-6.3 If the fracture occurs outside the middle tltirtl by more than 5 percent of the span length, the results discarded. C-7. of the span length of the test shall be REPORT C-7.1 The report shall include the following; number, 4 Identification b) Average width to the nearest 0.25 cm ( or 0.1 in ) 4 Average depth to the nearest 0.25 cm ( or O-1 in ), 4 Span length in centimetres or inches, e) Maximum applied load in kilograms or pounds, f j Modulus of rupture calculated to the nearest O-4 kg per sq em (or 5 lb per sq in ), Defects in specimen, and iit) 11)Age of specimen. 44...
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This document was uploaded on 10/01/2013.

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