Ductility Effects of End Details in Composite Beams

by Alan R. Kemp, Univ of the Witwatersrand, Johannesburg, South Africa,
Paolo Trinchero, Univ of the Witwatersrand, Johannesburg, South Africa,
Nick Dekker, Univ of the Witwatersrand, Johannesburg, South Africa,

Document Type: Proceeding Paper

Part of: Composite Construction in Steel and Concrete II


A limit states criterion is described for quantifying the rotation capacity of members in indeterminate structures as a means of classifying ductility of structures during plastic behaviour or overload conditions. The use of this criterion is illustrated by comparing the behaviour of long and short span specimens, representing the negative-moment region of continuous composite beams with rigid end connections, to similar beams detailed with semi-rigid end connections. These semi-rigid arrangements were simple, end-plate connections that behave as compositely continuous when the longitudinal reinforcement in the slab becomes effective. It is shown that the semi-rigid connections achieve considerably higher levels of ductility at similar moment resistances to the comparable beams with rigid, continuous connections. Components of rotation capacity ascribed to connection flexibility, cracking of the concrete and yielding of the steel section are identified and compared with theoretical predictions. The importance of lateral buckling in limiting ductility is demonstrated as well as the significant benefits in semi-rigid connections obtained by locating the plastic neutral axis close to the compression flange of the steel section.

Subject Headings: Composite beams | Structural behavior | Continuous beams | Ductility | Plastics | Connections (structural) | Steel structures | Steel

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