Title: Dynamics of freestanding flexible structures subjected to base excitations

Authors: Anupam Saraswat

Addresses: Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra, 400085, India

Abstract: Dynamics of a flexible structure, freely standing on a rigid base and subjected to base excitation is a complex problem. This paper presents experimental investigation of dynamics of a freestanding flexible structure subjected to base excitation. Two different steel structures viz. mechanical containment structure of a nuclear facility and a test specimen were tested on a shake table. Systematic study unveiled that free rocking frequencies of a flexible structure effect initiation of rocking motion from the rest state. Amplitude of base excitation required for initiation of rocking motion was observed to be much lower for base frequencies matching with free rocking frequencies whereas it was higher for all other frequencies Further, overturning instability was evaluated and represented by way of overturning curves Contrary to the present understanding of the subject, it was demonstrated that fundamental modal frequency had not affected rocking initiation whereas free rocking frequencies had.

Keywords: flexible body dynamics; free rocking frequencies; freestanding structure; seismic response; glove box; base excitation; rocking initiation.

DOI: 10.1504/IJEIE.2024.138639

International Journal of Earthquake and Impact Engineering, 2024 Vol.4 No.2, pp.154 - 181

Received: 26 Jul 2022
Accepted: 26 Aug 2022
Published online: 22 May 2024 *

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