Page 9 - June-2022

TECHNICAL PAPER

load-resisting capacity was observed. A sudden drop in the load load resisted by a specimen was twice its shear load. The
resistance was noted for the specimen L500-ST600 after reaching design normalized flexural strengths (M u /f ck bd) of Set-I and Set-II
the peak strength. The post-peak strength-reduction was specimens were computed as 0.18 and 0.14, respectively. The
relatively gradual in both L500-ST500 and L500-ST550 specimens peak normalized flexural resistance of the Set-I specimens
compared to the specimen L500-ST600. All three specimens was observed in the range of 0.25-0.27; whereas, the Set-II
had the same a/d ratios and failed in shear. All test specimens specimens exhibited the peak normalized flexural strengths
of Set-II exhibited significant post-yield displacements before of about 0.20. Since, the Set-II specimens showed flexure-
their failure. For the same a/d ratio as the Set-I specimens, the dominated behavior, it was inferred that the actual normalized
specimen L550-ST500 did not show any significant reduction flexural resistance was 1.43 times the design strengths. The
in the load-resisting capacity till a mid-span deflection of main parameters contributing to this difference were the
more than four times its yield displacement. The specimen material overstrength, strain-hardening, and partial safety
L550-ST550 having a nearly similar a/d ratio also exhibited the factor (or strength reduction factor) used in the design. The
ductile behavior but failed earlier to the specimen L550-ST500 design normalized shear strengths (V u /√f ck bd) of the Set-I and
indicating a reduced displacement ductility. Similarly, specimen Set-II specimens were computed as 0.43 and 0.39, respectively.
L550-ST600 also showed excellent post-yield deformation with a The observed value of normalized shear strengths of the
gradual reduction in the load resistance. Set-I specimens was about 1.5, which was about 3.5 times the
design value. Similarly, the observed values of normalized shear
Figure 4 shows the normalized load-deflection behavior of test strengths of the Set-II specimens were varied in the range of
specimens. The flexural resistance (M u ) and shear resistance 0.8-1.3, which was about 2.0-3.3 times their design values. A
(V u ) offered by the specimens are normalized with respect to smaller normalized strength was observed for the specimen
the concrete strength (f ck ) and area of cross-section. The total L550-ST600 having a higher a/d ratio as compared to other

0.30 0.30
f ck = 35 MPa f ck = 50 MPa L550-ST500
L550-ST550
0.24 0.24 L550-ST600
Design value
(0.18)
0.18 0.18

0.12 0.12
Design value
L500-ST500 (0.14)
0.06 L500-ST550 0.06
L500-ST600
0.00 0.00
0 3 6 9 12 0 10 20 30 40
Displacement at loading point (mm) Displacement at loading point (mm)

1.6 1.6 L550-ST500
f ck = 35 MPa f ck = 50 MPa L550-ST550
L550-ST600
1.2 1.2

L500-ST500
0.8 L500-ST550 0.8
L500-ST600

0.4 0.4
Design value Design value
(0.43) (0.39)
0.0 0.0
0 3 6 9 12 0 10 20 30 40
Displacement at loading point (mm) Displacement at loading point (mm)
(a) (b)
Figure 4: Load-deflection response of specimens: (a) Set-I; and (b) Set-II

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