Experimental and Analytical Investigation on Spiral and Circular Hoop Confinement of Concrete

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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.



Spiral, Circular, Analytical Investigation, Experimental, Hoop Confinement