Damage-avoidance self-centring steel rocking frames

Kibriya, L., Málaga-Chuquitaype, C. and Kashani, M. M. (2021) Damage-avoidance self-centring steel rocking frames. In, World Conference on Earthquake Engineering proceedings. (World Conference on Earthquake Engineering proceedings, 2021) International Association for Earthquake Engineering.

Abstract

This paper presents investigations on the dynamic behaviour of rocking steel frames that employ gap-opening mechanisms at the column-foundation and beam-column connections in order to avoid inelastic structural deformations under lateral loads. Current realizations of these structures incorporate supplementary energy-dissipation elements aimed at providing control against large demands. Therefore, they rely largely on yielding components that accumulate damage during strong dynamic action. Although the provision of yielding devices in rocking frames can improve their seismic performance in certain conditions, it obscures the understanding of their complex and unconventional nonlinear dynamics. Moreover, sacrificial yielding components often result in systems with permanent post-earthquake deformations that require non-negligible labour in terms of replacement, re-centring and/or repair. To address these shortcomings, this paper first examines the complex non-linear dynamics of pure rocking frames and proposes a Finite Element modelling framework that accurately represents their behaviour over a wide range of excitation frequencies and amplitudes. The methodology, applied to multi-storey steel frames, captures the presence of sub-harmonic resonances and higher modes. Additional demands due to the asymmetric member boundary conditions are identified in the rocking columns. The knowledge gained is then applied to develop a novel damage-avoidance solution by means of controlled elastic buckling of thin-walled tape-spring elements (similar to a carpenter’s tape) with curved cross-sections, often used as components of deployable spacecraft structures. Glass-Fibre Reinforced Polymer is selected as the material for the tape-spring members due to its high strength-to-weight ratio, elastic buckling properties, geometric design flexibility and tailorable performance. A numerical simulation protocol for the buckling members is developed and it is demonstrated that the system performs successfully under static and discrete sine-sweep loads for single-bay one and three-storey rocking frames. These concepts are extended to realistic multi-storey multi-bay rocking buildings. The performances of the proposed systems are compared to conventional steel moment frames. The buildings are subjected to a series of static load cycles, discrete sine-sweep ground motions, and earthquake records (using Incremental Dynamic Analysis). It is thereby demonstrated that Buckling-Enabled Composite Bracing enhances the static, non-linear dynamic, and seismic performance of rocking buildings by significantly reducing the member forces and other response quantities. Fragility analyses further demonstrate that rocking frames equipped with the proposed system exhibit lower probabilities of exceedance for the damage limit states involving storey drifts and accelerations, than conventional moment frames.

This record has no associated files available for download.

Contributors

Author: M. M. Kashani

Download statistics