Open Access

ARTICLE

Beam Approximation for Dynamic Analysis of Launch Vehicles Modelled as Stiffened Cylindrical Shells

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1 State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, International Center for Computational Mechanics, Dalian University of Technology, Dalian, China.
2 School of Engineering, University of Liverpool, Liverpool, UK.

* Corresponding Author: Yahui Zhang. Email: .

Computer Modeling in Engineering & Sciences 2020, 122(2), 571-591. https://doi.org/10.32604/cmes.2020.08789

Received 13 October 2019; Accepted 29 November 2019; Issue published 01 February 2020

Abstract

A beam approximation method for dynamic analysis of launch vehicles modelled as stiffened cylindrical shells is proposed. Firstly, an initial beam model of the stiffened cylindrical shell is established based on the cross-sectional area equivalence principle that represents the shell skin and its longitudinal ribs as a beam with annular cross-section, and the circumferential ribs as lumped masses at the nodes of the beam elements. Then, a fine finite element model (FE model) of the stiffened cylindrical shell is constructed and a modal analysis is carried out. Finally, the initial beam model is improved through model updating against the natural frequencies and mode shapes of the fine FE model of the shell. To facilitate the comparison between the mode shapes of the fine FE model of the stiffened shell and the equivalent beam model, a weighted nodal displacement coupling relationship is introduced. To prevent the design parameters used in model updating from converging to incorrect values, a pre-model updating procedure is added before the proper model updating. The results of two examples demonstrate that the beam approximation method presented in this paper can build equivalent beam models of stiffened cylindrical shells which can reflect the global longitudinal, lateral and torsional vibration characteristics very well in terms of the natural frequencies.

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