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Unformatted text preview: IAGRAMMATIC VIEW OF APPARATUS FOR FLEXURE TEST OF CONCRETE BY THIRDPOOINT LOADING METHOD C2.2 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
C2.2.1 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.
C3. TEST SPECIMEN C3.1 The test specimen
times its depth as tested.
C4. shall have a span as nearly as practicable three PROCEDURE C4.1 The test specimen shall be turned on its side with respect to its
The loadapplying
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 loadapplying
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: 4561957.
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.
c5. MEASUREMENT OF SPECIMENS AFTER TEST ES.1 Measurements to the nearest 0.25 cm ( or O1 in ) shall be made to
determine the average width and average depth of the specimen at the
section of failure.
C6. CALCULATIONS C6.1 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
C6.2 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 C6.1.
C6.3 If the fracture occurs outside the middle tltirtl
by more than 5 percent of the span length, the results
discarded.
C7. of the span length
of the test shall be REPORT C7.1 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 O1 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 O4 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.
 Fall '13

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