CRITICAL REVIEW OF SEISMIC DESIGN CRITERIA FOR CHEVRON CONCENTRICALLY BRACED FRAMES: THE ROLE OF THE BRACE-INTERCEPTED BEAM

Steel chevron concentrically braced frames are expected to dissipate seismic energy by yielding of the brace under tension, while both beam and columns behave elastically. Besides the strength, also the stiffness of the brace-intercepted beam plays a key role to avoid unfavourable mechanisms. However, no codified requirements are provided to assure adequate beam rigidity. In order to examine this aspect, in the first part of this paper the main results of a numerical parametric study devoted to investigate the mutual interaction between the beam vertical deflection and the brace ductility demand are described. The second part of this article investigates the efficiency of both EC8 and AISC341-10 seismic provisions on the global performance of chevron bracings, particularly focusing on the design of the beam of the braced bays. The results of incremental dynamic analyses performed on several structures confirm the primary importance of the flexural stiffness of the beam.