Seismic Yield Displacement Profile in Steel Eccentrically Braced Frames

Displacement-based methods are recognized as appropriate approaches to reach the goals of performance-based seismic design method. In the direct displacement-based seismic design method, the seismic yield displacement is applied as one of the important design parameters. In this paper, a new relation is suggested to determine the lateral displacement pattern at first yielding of eccentrically braced frame systems subjected to earthquake ground motions. This relation considers the influence of various structural features of frames. It is developed from the results of several nonlinear dynamic analyses containing 30 eccentrically braced frames under 15 far-field and near-field earthquake ground motions. Then, the results of these analyses are processed by nonlinear regression analysis in order to establish the most effective parameters on the yield displacement pattern of the frames. As a result, a comparison between the suggested yield displacement pattern and nonlinear dynamic analyses showed the efficiency and advantages of the suggested approach.