Page 8 - Open-Access-June-2020

TECHNICAL PAPER

and ductility of the panels. Further, the structural response of 3.1.2 Deflection and Ductility
the ECC deck panels was improved by altering the steel truss
substructure and the deflection of the panels were found to be Compared to RC beams without stirrups, the RECC beams
within the acceptable limit. without stirrups showed distinguished deflection due to the
multiple cracking behavior of ECC . The RECC beams with
[22]
Singh and Sivasubramanian investigated the flexural stirrups showed enhanced ductility than RC beams with stirrups
[31]
behavior of steel reinforced portal frames made of ECC and due to the strain-hardening behavior of ECC . The RECC
[34]
concrete under static transverse bending. The study reported beams without stirrups showed enhanced ductility index than RC
that in ECC frames, multiple micro-cracks and flexural tensile beams without stirrups . Addition of stirrups in FRP reinforced
[22]
failure occur. Finally, the study concluded that replacement of ECC beams increased the ductility significantly. However,
concrete by ECC exhibit enhanced load carrying capacity and when the transverse reinforcement ratio increases, the ductility
ductility. decreases due to the increased principle shear crack and
confinement of web stirrups .
[35]
3. SHEAR BEHAVIOR OF REINFORCED ECC
ELEMENTS 3.1.3 Cracking Behavior and Failure Modes

Generally, shear loads bring sudden brittle failure to concrete RECC beams exhibit more ductile shear failure than RC
[34]
elements. We understand that the shear failures are due to the beams . The FRP reinforced ECC beams with and without
diagonal tensile cracks. Though it is difficult to eliminate the stirrups, exhibit shear tension failure due to the splitting of
diagonal tensile cracks in shear field, it is certainly expected cracks . The crack width of RECC beams was reduced due to
[34]
that crack opening dramatically decreases by the effect of localized deformation of ECC [36,37] .
fiber bridging in ECC. This phenomena enhances the shear
performance of ECC structural elements such as load carrying The Iosipescu ECC shear beam geometry was successfully
capacity, deformation and ductility, energy dissipation and used and multiple cracks in ECC under pure shear were
[38]
damage tolerance. Hence, many research studies have demonstrated . In RECC beams, first cracking strength was
investigated the shear behavior of plain and RECC elements little higher than RC beams and the crack opening in RECC
such as beams, plates, panels and composite deck system as of beams were 10 times less than that of RC beams. Despite the
major interest. Some of the notable studies from the available configuration of transverse reinforcement, the crack width of
[34]
literature are presented in this section (see Table 2). RECC beams was smaller compared to RC beams . For main
shear crack, the average angle of 28.6°was observed . The
[37]
3.1 Shear Behavior of ECC Beams average crack width occurred was less than 100µm .
[39]
In order to understand the shear behavior of plain and RECC The RC beam without stirrups undergoes shear failure, whereas
beams, the parameters such as influences of load carrying in RECC beams the failure mode changes from shear to flexure
capacity and reinforcement ratio, stiffness and ductility, cracking which implies that the RECC beams without stirrups has superior
[22]
behavior and failure mode are to be explored. Significant shear resistance . Diagonal shear failure was observed in pure
[40]
research studies from the literature are discussed below in bending region of ECC beams without stirrups .
accordance with the above-mentioned parameters.
3.1.4 Influence of Shear-span Ratio
3.1.1 Presence of Shear Reinforcement and
Load carrying capacity The shear strength of the RECC beams is found to be higher
with increase in shear-span ratio. Increase in shear-span ratio
Compared to RC beams without shear stirrups, the RECC beams exhibits enhanced load carrying capacity, decreased ductility,
without shear stirrups showed distinguished load carrying energy dissipation and stiffness for steel reinforced ECC
capacity owing to the tensile strain-hardening property of beams . In case of FRP reinforced ECC beams, shorter shear-
[41]
ECC . The RECC beams with shear stirrups showed enhanced span exhibits increased load carrying capacity with decreased
[22]
load carrying capacity than RC beams with shear stirrups ductility due to the sudden shear-compression failure. Whereas
due to controlled crack deformation pattern offered by fiber ECC beams with longer shear-span, failed in shear-tension
bridging mechanisms in ECC which activates the main stirrup with enhanced deformation . Moreover, shorter shear-span
[35]
reinforcement at smaller crack widths . The FRP reinforced ECC depth ratios maybe allowed and encouraged in the case of
[34]
beams showed enhanced shear load carrying capacity than FRP FRP reinforced ECC beams, which is consciously avoided in RC
reinforced concrete beams with and without shear stirrups [12, 35] . beams when limit state is concerned .
[12]

The IndIan ConCreTe Journal | June 2020 9