Page 10 - Open-Access-July-2019

+

= + = + = + = = = + + + = = + +

TECHNICAL PAPER = + = = +
= = = = +
ductility. Displacement ductility factor can be defined as the Another model was proposed by Ho et al. [19] for the peak
=
=

=
=
=

=

ratio of lateral deflection of the structure at ultimate load, load of ferrocement confined reinforced concrete columns. The
+
=

=

to lateral deflection at first yield. Since the load-deflection equations are as follows:

=
behaviour is not perfectly elasto-plastic, yield displacement is =
taken by assuming elastic behaviour of cracked section up to = ( + ) + (3)
)
the theoretical ultimate strength of the column [17] . From the ) + = = = (( ( + + + ) + + ,
) +
) + + (
(
+ =
( =
=
) + +
(
) +
=
+
obtained values, ductility factor is calculated as given in Table where , , , and = are the contributions of RC columns, ;
) +
+
=
(
,
5. There is a significant improvement in ductility in ferrocement ferrocement and longitudinal reinforcement respectively; K is a ; ;
,
)
,
,
+
, +
=
(
) +
and +
=
confined specimens. coefficient and a function of ; , ( ; and ; are the lateral ; ;
(
) +
+
=
,
confining pressures generated by transverse reinforcement and ;

table 5: Displacement ductility factor of control and ferrocement, respectively. ( + , , ) + . ; ;
=

..
confined columns , 1− 0.375 + ;
1− 0.375
. . = . , 1− 0.375 . + + + . . .
1− 0.375
,,
spEcImEn dEflEctIon dEflEctIon dIsplacEmEnt = = + 0.375 + + 847.385 1− 0.375 + ;

1−
+1.349
1− 0.375 1− 0.375 ,
..
,
at fIrst at ultImatE , ductIlItY, = , .. . , 1− 0.375 (4) , . +
,
.
=
=
=
+1.349
+1.349
847.385

+1.349
847.385
cracK load, load, ∆ u (mm) ∆ u / ∆ Y . . . . 847.385 . = ,, , , . 1− 0.375 , ,, . . + . .
+1.349 +1.349 +1.349
.
∆ Y (mm) 847.385 847.385 847.385 , , , =0.5 = , 847.385 , 1− 0.375 , + .
,
,
+1.349 .
,
+1.349
=0.5
.
=0.5 = , , 847.385 ,1− 0.375 . ,+
=
C1 3.78 5.78 1.53 =0.5 = 847.385 . .
,
+1.349 .
=0.5 =0.5 =0.5 ,, =0.5 , 1− 0.375 . + (5)
=
,
+1.349
847.385
S1 2.25 = 4.61 + = + 2.05 = = = , =0.5 . 847.385 , +1.349 , .
,
=
= , = , = , =0.5 =0.064 , +26.92 . , . ,
=
,
C2 5.77 10.31 1.78 .. . = =0.5 847.385 , , +1.349
,
=0.064
+26.92
+26.92
=0.064
. . . =0.064 ,, , , +26.92 ,, , (6) ,
S2 3.98 8.82 2.22 = =0.5 .
+26.92 +26.92 +26.92
=0.064 =0.064 =0.064 , , , , = =0.5 =0.064 , , . +26.92 ,
=
,
,
,
=
,
=
,
4. cONFINeMeNt MODeLs = = = = = = =0.064 =0.064 . +26.92 . . +26.92 , (7)
= =
=
,
,
=
+26.92
=0.064
Confined concrete performs differently based on the type of = = = = =0.064 . , , +26.92 , ,

=
=
=
=
materials used. So, attempts were made to develop analytical = =0.064 = , +26.92 , (8)
models for confined concrete of various materials. Existing = = = .

analytical models for confined concrete can be categorised = =1 − 0.513
=

into two types: design and analysis oriented models. Design ) + =1 − 0.513 = .. . =
+=
(
) + +
(
=

(9)

=1 − 0.513
.
oriented models are empirical in nature and are developed . . =1 − 0.513
.
,
,
=1 − 0.513 =1 − 0.513 − 0.513

=1
=1 − 0.513

.
by fitting the experimental data, whereas analysis oriented ; and in the form of
and
K is expressed as a function of ;
=1 − 0.513

models are developed using numerical analysis approach which =1 − 0.513 .

.
is challenging. Existing models for predicting the ultimate =1 − 0.513 . .
(10)

=1 − 0.513
strength of circular reinforced concrete columns confined =1 − 0.513

with ferrocement jacket are proposed mainly on the basis of
. .
experimental findings obtained by researchers and hence are, Existing models for predicting the strength of circular reinforced
+
+
1− 0.3751− 0.375

,
,
design oriented. Only two models were developed for circular concrete columns confined with ferrocement jacket at ultimate
=
=

.
.
.
.

reinforced concrete columns. 847.385 847.385 strength are proposed mainly on the basis of experimental
+1.349 +1.349
,
,
,
,
findings obtained by researchers. The confinement models
Kaushik and Singh [18] proposed analytical models for calculating given in the above section were used to calculate the peak
=0.5
=0.5
strength of circular reinforced concrete columns jacketed with strength of recycled aggregate concrete specimens confined
,
,
=
=
ferrocement at peak strength. The formula proposed is as with ferrocement. The values for ultimate load carrying capacity
follows: . . of recycled aggregate columns confined with ferrocement were
=0.064 =0.064 +26.92 +26.92
, obtained using the two existing confinement models for normal
= + , , (1) ,
aggregate columns with ferrocement confinement. The values
= = are compared with those obtained from the experiments. It is

σ c and σ o are the strengths of confined and unconfined observed that slightly larger values are obtained from analytical

concrete, respectively; σ L is the lateral confining pressure; k’ is models compared to experimental results. This is probably
=

+ =
=
the strength increase factor with a value of 4.2. Lateral confining due to the strength reduction of confined specimens due to
=

pressure provided by transverse reinforcement is given by the recycled aggregates. By suitably modifying the coefficients

following formula:
in the analytical model, they can be applied to the analysis
. (2) . of specimens with recycled aggregates. Table 6 shows the
= =1 − 0.513=1 − 0.513
comparison between analytical and experimental results.
= ( + ) +
24 The IndIan ConCreTe Journal | JulY 2019
,

;
= ( + ) +
,
;
.
1− 0.375 +
= ,
. .
847.385 , +1.349 . ,
1− 0.375 +
=0.5 , . .
=
= , 847.385 , +1.349 ,
=0.5
=0.064 , . +26.92 ,
= ,
=
.
=0.064 , +26.92 ,
=
=
=
.
=1 − 0.513
.
=1 − 0.513