Confinement effectiveness in concrete structures

From the beginning of the 19th century, confined concrete is a popular topic among researchers. This is because, the ductile behaviour and strength of the concrete increases, when it is confined. Hence confinement effect is considered in seismic design of concrete structures. To find the strength enhancement due to confinement, various models have been proposed. Some of these models are Mander's model, Shah's model and modified L-L model. These models were developed for concrete confined by spiral reinforcement, (the spiral reinforcement was anchored to the main reinforcement bars). Almost all the experiments in the past on concrete confined with spiral reinforcement were carried out anchoring the spiral reinforcement to the main reinforcement bars. In the present study experiments were carried out without fixing the spiral to the main reinforcement bars. The obtained experimental results were compared with the available models. It was found that modified L-L model was very close to the results obtained. Some applications that could use the confinement effect, such as increasing the column load carrying capacity in post construction stage and using spiral reinforcement to increase shear resistance in beams and flat slabs (punching shear) were discussed. Then the experimental results by using spiral as shear resistors were given and it was compared with the confinement effectiveness of the spiral. Areas identified for the future works have also been highlighted as ecommendations for future work