Shear capacity of reinforced concrete corbels using mechanism analysis

A mechanism analysis is developed to predict the shear capacity of reinforced concrete corbels. Based on shear failure observed in experimental tests, kinematically admissible failure mechanisms are idealised as an assemblage of two rigid blocks separated by a failure plane of displacement discontinuity. Shear capacity predictions obtained from the developed mechanism analysis are in better agreement with corbel test results of a comprehensive database compiled from the available literature than other existing models for corbels. The developed mechanism model shows that the shear capacity of corbels generally decreases with the increase of shear span-to-depth ratio, increases with the increase of main longitudinal reinforcement up to a certain limit beyond which it remains constant, and decreases with the increase of horizontal applied loads. It also demonstrates that the smaller the shear span-to-overall depth ratio of corbels, the more effective the horizontal shear reinforcement

Shear behaviour of pile cap strengthened with carbon fibre reinforced polymers

A pile cap is typically a disturbed region with a very small shear span to depth ratio. Flexural theory for reinforced concrete structures cannot be applied to interpret the behaviour of a pile cap because of the non-uniform stress distribution over the depth. In this research, two series of pile caps were designed with different effective depths using strut-and-tie modelling (STM). Three scaled pile caps were cast for each series and tested under monotonic concentrated load until failure to observe the ultimate shear strength. Two additional series of pile caps strengthened with carbon fibre reinforced polymer (CFRP) with exactly the same geometric and design parameters as the control series were cast to observe the shear strength enhancement in comparison with the control specimens. STM proved to be a reliable solution for predicting the shear strength of the pile caps. The application of CFRP resulted in a 15-17% enhancement in the shear strength of the pile caps. It was also found that different prediction models for the evaluation of shear enhancement in beams can be used in the case of pile caps