Evening Meeting: High-strength concrete columns: a design guide

The use of high-strength concrete (HSC) has increased significantly in recent years due to its improved performance characteristics when compared with normal-strength concrete (NSC). Current design codes, however, are predominantly based on data derived from tests on NSC. Furthermore, the extrapolation of NSC design rules to HSC is not always conservative and can lead to unsafe designs.

Extensions to the NSC provisions of current codes to encompass HSC have been published, but their advice is often ignored by engineers, because either their recommendations are not mandatory, or the codes do not give clear direction on their limitations.

This paper compares the behaviour of HSC with NSC and highlights the brittle nature of HSC under axial loading. Specific design and detailing requirements for achieving adequate ductility in HSC columns are reviewed and discussed. The paper describes how sufficient ductility can be achieved by using an appropriate confining pressure provided by the column links. A typical design example and RC details are included to illustrate how an appropriate level of ductility can be achieved.

Angus McFarlane, BSc, MSc, CEng, FIStructE, FICE
Technical Director, Hyder Consulting Middle East