Wound FRP for concrete beams with optimised geometries

Fabric formwork is a casting system that uses woven fabrics as the mould for concrete, utilising the fluidity of concrete to create optimised structural geometries. Fabric formed beams normally have variable depth along their longitudinal axis which makes it extremely time and labour consuming to install steel shear links because of this changing geometry. We propose the use of Wound Fibre Reinforced Polymer (WFRP) in which carbon fibres tows coated in wet epoxy matrix are wound around the longitudinal reinforcement to create uniquely shaped reinforcement cages as a practical alternative to steel shear links. In this work, eight tapered beams with varying reinforcement ratios were tested. All the specimens have same clear span and shear span/depth ratio. The influence of the shear reinforcement ratio and the shear reinforcement pattern were investigated. A Modified Compression Field Theory (MCFT) model was built to simulate the performance of the tests. The design codes (ACI 440 2007 and CSA S806 2012) as well as the MCFT model were assessed by the testing results. It is found that the application of WFRP in concrete beams is successful. The fabrication process of the reinforcement cage was easy to construct and enables the fabrication of reinforcement for optimised beam geometries. The test specimens failed in the predicted failure modes and the WFRP can increase shear capacity up to 250%. The MCFT model works more accurately than the two design codes. The shear reinforcement pattern plays an important role in the shear design and there is great potential to optimise the WFRP pattern.