Evaluation of the Italian seismic code for the design of concentrically V-braced steel structures

A critical analysis of the design methods provided by the current Italian technical code for constructions NTC2008 [1] for steel structures with V braces is carried out, with the aim of providing simplified and more efficient design criteria able to ensure adequate safety under seism. The need of incorporating and merging all the most updated achievements of research related to the design of seismic resistant systems motivated the Italian project RELUIS-DPC (2010-2013), specifically focused on these issues. In particular the research unit UNINA-ING task was the optimization of design criteria for seismic resistant steel braced structures. First results of this activity were provided in De Lucia et al. [2] and Macillo et al. [3], with respective reference to Chevron (or inverted V) and X-braced structures, the latter being described in Macillo et al. [4]. As the same, the present work is divided in two parts. The first one consists in the design, according to standard rules, of typical steel V braced structures, by linear analysis, both static and dynamic. The aims is identifying any possible weakness in the current design criteria, with particular reference to both the applicability of the proposed procedures and the actual possibility to size the bracing cross-sections. Based on the review observations, alternative design methodologies are proposed. The second phase consists in the assessment of the seismic response of examined structures designed according to either NTC 2008 or alternative methods. To this purpose, nonlinear static analyses are performed in order to evaluate the most relevant behavioural issues, like the behaviour factor, the failure modes and the effectiveness of the capacity design rules.