Direct Displacement-Based Seismic Design of Eccentrically Braced Steel Frames

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Direct Displacement-Based Seismic Design of Eccentrically Braced Steel Frames

Gerard J. O’Reilly & Timothy J. Sullivan

Abstract

A series of eccentrically braced frames (EBF) are designed and subjected to nonlinear analyses

to highlight ambiguities and differences in current seismic design provisions for EBF structures.

This provides motivation to implement better guidance for the checking of local displacement

demand considerations and move towards a displacement-based design approach. A recently

proposed direct displacement-based design (DDBD) procedure for EBFs is then described and

further developed in this paper through the calibration of a spectral displacement reduction

factors that relate the displacement of an inelastically responding structure to that of the

equivalent linear representation used in the DDBD of EBFs. Such an expression is calibrated as

part of this study using an experimentally validated numerical model also proposed here for the

EBF links such that the actual hysteretic behaviour of the links is well represented. The DDBD

guidelines are applied to EBF systems from 1 to 15 storeys in height and their performance is

verified via nonlinear dynamic analyses using two different sets of design spectrum compatible

ground motions. The results of the study indicate the robustness of the proposed DDBD method

in limiting the interstorey drifts to design limits for a variety of EBF systems with short links,

thus demonstrating that the proposed DDBD method is an effective tool for seismic design of

EBFs.

 

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