Ductility of composite beams under negative bending: an equivalence index for reinforcing steel classification

Reinforcing steel actually available on the European market is generally characterised by a good strength, but also by reduced ductility; on the other hand European codes concerning concrete and composite structures point out the importance of using reinforcing steel with sufficient ductility. In this paper, the influence of the properties of reinforcing steel on the rotational capacity of composite beams under negative bending is theoretically analysed using a refined model, validated with experimental tests. An equivalence criterion for the classification of reinforcing steel is also introduced. Plastic rotation that can be sustained by composite beams at failure is assumed as the main parameter to define the equivalent structural performance. To this end, the results of a wide parametric analysis are discussed. The comparison with similar analyses made for concrete structures shows that one classification for reinforcing steel seems to be not reliable for both types of structures. (C) 2001 Elsevier Science Ltd. All rights reserved