Model for Concrete Confined By Aramid FRP

Hau-Yan Leung

Dept of Civil Engineering, Chu Hai College, Hong Kong

Chris Burgoyne

Department of Engineering, University of Cambridge, UK

The advent of Fibre Reinforced Plastic (FRP) as reinforcement or as prestressing tendons for concrete has many attractions, since they are more durable than steel. However, they show no ductility before failure (although their large strain capacity normally means they are unlikely to snap), which means that beams will normally be designed to be over-reinforced. Thus, instead of failure being initiated by yielding of the steel, with the concrete failing later, it will be caused by crushing of the concrete. Hitherto it has been enough to say that the concrete has sufficient strength, without requiring too much understanding of the actual failure process, but if the concrete is going to fail first more detail is required.

It is also desirable for the concrete to have greater ductility, and to this end, it has been suggested that spirals of reinforcement should be included in the compression zone (with their axes aligned parallel to the compressive force) to provide additional confinement; if fibre reinforced plastics (FRPs) are being used as the tension reinforcement it is logical to use them also for the hoop reinforcement. Although rectangular links can be made from steel, they are not ideal for Fibre Reinforced Plastic (FRP) because of strength loss in the corners, and they are anyway less efficient at generating confining stress than circular links.

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