Page 16 - Open-Access-June-2020

TECHNICAL PAPER

Depending upon the thickness of ECC layer, the cracking modes are investigated. After considering the above-mentioned
behavior differs significantly. The crack width of the ECC parameters, the notable research studies available in the
strengthened RC beams decreased with increase in ECC layer literature are presented in the following section.
thickness compared to unstrengthened RC beams due to the
multiple cracking behavior of ECC . 9.1.1 Influence of shear Reinforcement
[63]
Compared to RC beams the yielding of stirrups was larger for
8. SHEAR BEHAVIOR OF ECC RECC beams due to the shear resistance property of ECC .
[78]
STRENGTHENED RC BEAMS The RECC beams also showed enhanced load carrying capacity
It is expected that the tensile strength and pseudo-strain- even in the absence of shear stirrups due to the superior shear
[79]
hardening behavior of ECC can be exploited for shear capacity of ECC . In accordance with displacement capacity,
strengthening applications in RC elements. However, only very the maximum drift was enhanced for ECC coupling beams
few researchers have investigated the shear performance of ECC with diagonal reinforcement than ECC coupling beams without
[80]
strengthened RC elements (see Table 7) with principle attention. diagonal reinforcement .
Kim et al. used ECC layers (in terms of cover thickness) at 9.1.2 Influence on the Hysteresis Loop
[77]
tensile zone of the RC beam in order to increase the shear
capacity with and without shear stirrups. The study showed no Due to the enhanced deformation behavior of ECC, the
significant improvement in shear load carrying capacity of the hysteresis loop of RECC beams was larger compared to RC
[79]
beams with varying cover thickness of strengthening. Finally, beams . The hysteresis loop of RECC coupling beams without
the study concluded that the amount and the type of repairing diagonal reinforcement showed less pinching compared to
[80]
material used were not significant factors in improving shear RC coupling beams with diagonal reinforcement . Typical
capacity of RC beams. Besides delaying, the interface failure was hysteresis loop of RC and RECC beams is shown in Fig. 4.
to be considered as the main factor.
9.1.3 Energy Dissipation Capacity
9. SEISMIC BEHAVIOR OF ECC ELEMENTS RECC beams showed enhanced ductility with large amount of
energy dissipation compared to RC beams . The RECC beams
[78]
The tensile strain-hardening behavior makes ECC as a superior without stirrups exhibits enhanced energy dissipation capacity
construction material than conventional concrete in seismic than that of RC beams with dense stirrups . In RECC beams,
[79]
resistance applications. Hence, many research studies (see the energy dissipated was less sensitive to various deformation
Table 8) have investigated the seismic behavior of ECC [81]
structural elements. Applications, which are briefly discussed histories unlike RC beams . Compared to RC coupling beams
with diagonal reinforcement, the RECC coupling beams without
in this section, include behavior of various elements such as
beams, columns, beam-column connections, walls, panels and diagonal reinforcement showed decreased energy dissipation
[80]
other special elements subjected to displacement reversals. capacity due to the pinching effect .
Elaborated discussion on seismic application and design of ECC 9.1.4 Cracking Behavior and Failure Mode
structures can also be learned from Lijun et al. [106] .
In RECC beams many flexural and shear cracks are formed
9.1 Seismic Behavior of Various ECC Beam simultaneously than RC beams due to the multiple cracking
[78]
Elements behavior of ECC . The crack width in RECC beams was reduced
tremendously than RC beams . Moreover, in RC beams, the
[79]
In order to understand the seismic behavior of ECC beams, the residual splitting crack length was twice that of RECC beams
following parameters such as influence of shear reinforcement, [81] . In case of coupling beams, multiple diagonal cracks was
hysteresis and energy dissipation, cracking behavior and failure observed till the fiber pullout .
[80]
Table 7: Shear Behavior of ECC Strengthened RC Beams
dimensions eCC
sl. type of * loCation
no. referenCe reinforCement (b×d×l) of eCC thiCkness oBjeCtive oBservations
(mm) (mm)
1. Kim et al. [77] steel 160×160×1400 soffit 25 & 50 To investigate the shear The shear strength and
behavior of ECC repaired deflection capacity of twice
RC beams cover thickness beam with
stirrups were approximately
2 times greater than that of
specimens without stirrups.
* (b-breadth, d-depth & l-length)

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