Finite element investigation of multi-story post-tensioned rocking frames

Kibriya, L. T., Málaga-Chuquitaype, C., Kashani, M. M. and Alexander, N. A. (2018) Finite element investigation of multi-story post-tensioned rocking frames. In 11th National Conference on Earthquake Engineering 2018, NCEE 2018: Integrating Science, Engineering, and Policy. vol. 8, Earthquake Engineering Research Institute. pp. 5250-5260 .

Abstract

Modern code-conforming buildings have a high probability of surviving major seismic events without collapse, hence minimizing the number of casualties. Nevertheless, the risk of substantial post-earthquake economic losses remains high, as a consequence of inadequate damage prevention guidelines in current earthquake design codes. Rocking post-tensioned moment-resisting frames present a viable damage-free structural solution, with a nominal increase in building costs compared with conventional buildings. This structural system comprises of: (i) unbonded post-tensioned strands to provide overturning resistance and self-centering capability, and (ii) opening joints at the column-foundation and beam-column interfaces designed to rock during a seismic event. Rocking frames with various forms of supplemental damping have been previously examined numerically, adopting different finite element frameworks. However, there is a shortage of numerical studies studying the non-linear dynamic response of pure rocking multi-story post-tensioned moment frames, exclusive of supplementary energy-dissipation elements and devices. Hence, it is critical to develop modelling procedures for multiple stories which adequately capture the full range of their nonlinear dynamic behavior due to the joint rocking mechanism, and investigate the resulting response. Numerical studies are presented herein, including static and dynamic analyses of three- to nine-story building models. The proposed modelling methods are shown to effectively predict the non-linear response of multi-story rocking frames over a wide range of forcing frequencies and amplitudes. It is further concluded that the structural response is influenced by both sub-harmonic resonances and beam-column interactions.

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Contributors

Author: M. M. Kashani

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