Stochastic optimisation of buckling restrained braced frames under seismic loading

Abstract

A stochastic optimisation procedure is proposed for the design of low- and mid-rise buckling restrained braced frames subject to seismic loading. The seismic excitation is represented as a zero-mean nonstationary filtered white noise. The Bouc–Wen model is chosen to represent the hysteretic behaviour of the buckling restrained braces. The equivalent linearisation method is employed to determine the second-order statistics of structural responses from the non-linear system. Three seismic intensity levels are considered in this study, which are associated to earthquakes with different probability of occurrence during the building’s lifecycle. It was observed that the optimal design that minimises the maximum ductility demand produces a more uniform distribution of energy dissipation and avoids soft-storey mechanisms; therefore, this design objective is considered to be a more reasonable optimisation objective for the design of buckling restrained braced frames. For higher rise structures, buckling restrained braces may experience over-dimensioning in the top stories, which means that dissipation will not occur. Thus, an upper bound constraint for the stiffness design of the buckling restrained braces is taken into account.

Keywords:

• Structural optimisation
• buckling restrained braced frames
• seismic response
• stochastic seismic loading
• hysteretic behaviour

Acknowledgements

The financial support of National Natural Science Foundation of China (NSFC) through the Major Research Plan (grant number 51638012) is gratefully acknowledged. The first author gratefully acknowledges the support of the China Scholarship Council to allow the first author to visit the University of Illinois at Urbana-Champaign. The second author gratefully acknowledges the financial support of CONICYT-Chile through the Becas Chile Scholarship No. 72140204, and Universidad Tecnica Federico Santa Maria (Valparaiso, Chile) through the Faculty Development Program Scholarship No. 208-13.