Shortcomings of code methods for shear design of rc structures and the possible role of fibres

摘要

This paper makes use of data obtained from tests on simply-supported reinforced-concrete beams with an overhang, which were designed in compliance with the earthquake-resistant design clauses of the European codes EC 2 and EC 8. The test data reveal that increasing the amount of link reinforcement within the critical regions beyond the amount required to safeguard against shear failure does not lead to beam behaviour that satisfies the performance requirements for strength and ductility specified by the codes. This experimental evidence is complemented by an analytical investigation based on nonlinear finite-element analysis, which not only shows that the causes of the measured and observed specimen behaviour relate to the brittle nature of concrete at the material level, but also demonstrates that imparting concrete with strain-softening characteristics - through, for example, the inclusion of fibres - produces a significant increase in both load-carrying capacity and ductility.