Updating finite element models considering environmental impacts

Abstract

Structures are always exposed to the surrounding environment. The environmental variability (especially fluctuation in temperature) creates noticeable variations in structural modal properties. Two major mechanisms from temperature can cause uncertainties in natural frequency and mode shape measurements: i) the changes of material properties (elastic modulus) by temperature variation, and ii) the stress stiffening effects by temperature induced axial loading. Also, changes of boundary condition may cause variation in modal properties as well. In model updating, not considering these environmental effects may cause false identification on structural damage, thus compromises the accuracy of the updating results. This study presents a finite element model updating technique which can address the issue of varying environment including temperature variation and boundary condition changes. Temperature and boundary condition information is incorporated into the stiffness formulation of the finite element model. A numerical study on updating a bridge model subjected to damage and environmental changes is presented to demonstrate the effectiveness of the proposed method.