Page 42 - ICJ Jan 2023

TECHNICAL PAPER COLLECTOR’S EDITION

Fig 7 Position of cracks in Beam B 7

were obtained in a region of a web opening than in Crack pattern: The first crack appeared either from
regions having no openings. The maximum strain the left side opening or from right side opening of
-5
measured during the test was 700 x 10 . the beams having openings in shear span. This is
due to shear concentration in the corners of the
In early stages of loading, load was applied, then openings. It is more true for the left corner of the
removed to study the residual deflection resulting left side opening and right corner of the right side
from loading. It was found that the residual opening Figs 4 and 5. These shear cracks propagated
deflection corresponding to various levels of
loading was of the order of 15 to 20 percent of the towards the support. Beams having openings in
total produced by the particular loading. the constant moment zone did not exhibit crack
propagation from the corner of the opening Figs

The beams were unloaded after the failure load 6 and 7. It appears stress concentration is not very
was reached. These beams were reloaded again; significant as far as bending is concerned. Fewer
the observed failure load after reloading was of the cracks were observed in beams having openings
order of 60 to 70 percent of the ultimate load. This in shear span than beams having openings in
is an important characteristic for beams subjected constant moment region.
to accidental overloads, thus showing the resilient
behaviour of these beams.
Load-deflection curve: Fig. 8 shows that there is
INTERPRETATION OF TEST RESULTS not a significant difference in deflection between
beams with openings and without openings. The
The significance of these tests is best illustrated by
comparing the behaviour of these beams with an maximum deviation is of the order of 20 percent.
identical beam without any opening. The principal The deflections at working loads in all these cases
test results are presented in Table 2. were well within the permissible values.

The Indian Concrete Journal | November 2018 43