Seismic design methods for concentrically braced frames

The present paper is intended to point out the main differences existing among the seismic design procedures for concentrically braced frames contained in different seismic design codes. Two ten storeyed concentrically braced frames were designed taking into consideration the provisions of three seismic design codes: the Romanian norm P100-1/2013 [1], the European standard EN 1998-1:2004 [2] (respectively SR EN 1998-1:2005 [3]) and the American code AISC 341-16 [4]. All structural members of the concentrically braced frames (braces, beams and columns) had built up I-shaped cross-sections, sized according to the provisions of SR EN 1993-1-1:2006 [5]. Each designed frame was subjected to static nonlinear analyses. The seismic design loading state in different kind of structural members and the estimated steel consumption, the maximum values of base shear forces and horizontal floor displacements were compared. The successive formation of plastic hinges and the plastic failure mechanism in the different designed frames was analysed. A configuration with additional potentially plastic zones along the frame girders was proposed in order to improve the behaviour of the concentrically braced frames during static and dynamic nonlinear analyses.