Comparative study regarding the seismic design of diagonal concentrically braced frames

The present paper analyses some possibilities to improve the provisions concerning the seismic design of diagonal braced frames according to the in charge European and Romanian seismic design code (EN 1998‐1:2004 [1], respectively P100‐1/2013 [2]). Three design variants were used for the dimensioning under seismic actions of two ten story concentrically braced frames, taking into consideration different contributions of the tensioned and compressed braces in carrying horizontal seismic forces. The considered braced frames had two spans of 6.0m and ten storey of 3.5m. One of the frames had ascendant diagonal braces (from the lateral columns to the central column) and the other had descendant diagonal bracings (from the lateral columns to the central column). Static nonlinear analyses were performed with all the designed variants of the frames. The loading and deformation states at different steps during the analyses were compared. The distribution of plastic hinges in the structure was analysed. A more favourable behaviour of the frame during static nonlinear analysis was ensured by providing reduced cross‐sections along all frame girders ends (resembling the dog‐bone detail).