Ductility classes in prEN 1998‐1. Comparative analysis on concentrically braced frames

In case of severe earthquakes, a ductile behaviour of the structure is desirable. The post‐elastic behaviour ability of a structure is generally managed in seismic design codes by means of the ductility class of the structure. The future version of the European standard prEN 1998‐1‐1 [1] defines three such classes, DC1, DC2 and DC3, with different meanings than the existing DCL, DCM and DCH in the current version of EN 1998‐1 [2]. A question that arises is whether a less elaborated structural analysis and design, involved by DC1 or even DC2 structures could finally lead to a more cost‐effective solution than a DC3 structure, which requires more sophisticated analyses and more careful design. Several answers can be obtained for each type of structural system. This paper focuses on the differences that can be highlighted in the design of concentrically braced frames according to the three new approaches. A concentrically braced structure was analysed to test the results for the three possible approaches. Three solutions were obtained using the requirements defined for DC1, DC2 and DC3. All three structures were designed based on resistance requirements. The material consumption and the post‐elastic behaviour were observed for each one of the three structural solutions.