Experimental and Analytical Investigation on Spiral and Circular Hoop Confinement of Concrete
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Date
2018-06
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Publisher
AAU
Abstract
Confining of concrete using transverse reinforcement is common trend in construction
industry in order to enhance strength as well as achieving of ductility; with ductile behavior of
failure mechanism. Therefore, there are two types of passive confinement techniques which are
practically adopted for circular cross – section of columns; these are called spiral and circular
hoop. To examine the difference between spiral and hoop confinements, forty four cylindrical
concrete specimens with a size of 300mm in height and 150mm in diameter are scrutinized
experimentally. The experiment embraces three groups of specimens; cylindrical concrete
specimens confined by spiral, circular hoops, and unconfined cylindrical column specimens. For
first and second groups vertical spacing and yield strength of transverse reinforcement are main
variables, in addition to these, unconfined compressive strength of concrete is considered as
variable for all groups. Supplementary to the experimental specimens, ten different combinations
of concrete specimens are simulated using Finite Element Package.
About 5% increase of confined strength of concrete by circular hoops over spiral
confinement at 56mm spacing of transverse reinforcement was observed. The percentage
increase of confined strength of concrete by spiral over circular hoops at 94mm spacing of
transverse reinforcement is about 11%. It can be concluded that spiral reinforcements offer better
confined strength than circular hoops at relatively large spacing and vice versa.
Sensitivity analysis was also conducted by considering confined strength of concrete as
objective function. Based on the analysis, compressive strength of concrete has largest
contribution than other variables. On the other hand, spacing of transverse reinforcement has an
adverse effect to confined strength of concrete in both of spiral and circular hoop confinements.
The contribution of yield strength of transverse reinforcement is relatively smaller than other
variables.
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Keywords
Spiral, Circular, Analytical Investigation, Experimental, Hoop Confinement