On the derivation of structural models with general thermomechanical prestress

TL;DR

This paper develops a novel method to derive models for thin structures with general thermomechanical prestress, incorporating nonlinear effects, damping, and thermal influences, using an innovative variational approach based on a modified Hu-Washizu functional.

Contribution

It introduces a new derivation procedure for thin prestressed structures from 3D mechanics, including thermal effects and damping, using a modified variational functional and strain measures.

Findings

Derived lower-dimensional models for thin beams with prestress and damping.

Provided a clear interpretation of small perturbations and moderate rotations.

Applied the method to thin beams demonstrating its effectiveness.

Abstract

The vibrating behaviour of thin structures is affected by prestress states. Hence, the effects of thermal prestress are important research subjects in view of ambient vibration monitoring of civil structures. The interaction between prestress, geometrically non-linear behaviour, as well as damping and its coupling with the aforementioned phenomena has to be taken into account for a comprehensive understanding of the structural behaviour. Since the literature on this subject lacks a clear procedure to derive models of thin prestressed and damped structures from 3D continuum mechanics, this paper presents a new derivation of models for thin structures accounting for generic prestress, moderate rotations and viscous damping. Although inspired by classical approaches, the proposed procedure is quite different, because of (i) the definition of a modified Hu-Washizu (H-W) functional, accounting for stress constraints associated with Lagrange multipliers, in order to derive lower-dimensional models in a convenient way; (ii) an original definition of a (mechanical and thermal) strain measure and a rotation measure enabling one to identify the main terms in the strain energy and to derive a cascade of lower-dimensional models (iii) a new definition of "strain-rotation domains" providing a clear interpretation of the classical assumptions of "small perturbations" and "small strains and moderate rotations"; (iv) the introduction of a pseudo-potential with stress constraints to account for viscous damping. The proposed procedure is applied to thin beams.