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Multi-scale model updating of a timber footbridge using experimental vibration data

Rafael Castro-Triguero (Department of Mechanics, University of Cordoba, Cordoba, Spain)
Enrique Garcia-Macias (University of Seville, Seville, Spain)
Erick Saavedra Flores (University of Santiago, Santiago, Chile)
M.I. Friswell (College of Engineering, Swansea University, Swansea, UK)
Rafael Gallego (University of Granada, Granada, Spain)

Engineering Computations

ISSN: 0264-4401

Article publication date: 2 May 2017

215

Abstract

Purpose

The purpose of this paper is to capture the actual structural behavior of the longest timber footbridge in Spain by means of a multi-scale model updating approach in conjunction with ambient vibration tests.

Design/methodology/approach

In a first stage, a numerical pre-test analysis of the full bridge is performed, using standard beam-type finite elements with isotropic material properties. This approach offers a first structural model in which optimal sensor placement (OSP) methodologies are applied to improve the system identification process. In particular, the effective independence (EFI) method is used to determine the optimal locations of a set of sensors. Ambient vibration tests are conducted to determine experimentally the modal characteristics of the structure. The identified modal parameters are compared with those values obtained from this preliminary model. To improve the accuracy of the numerical predictions, the material response is modeled by means of a homogenization-based multi-scale computational approach. In a second stage, the structure is modeled by means of three-dimensional solid elements with the above material definition, capturing realistically the full orthotropic mechanical properties of wood. A genetic algorithm (GA) technique is adopted to calibrate the micromechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally.

Findings

An overall good agreement is found between the results of the updated numerical simulations and the corresponding experimental measurements. The longitudinal and transverse Young's moduli, sliding and rolling shear moduli, density and natural frequencies are computed by the present approach. The obtained results reveal the potential predictive capabilities of the present GA/multi-scale/experimental approach to capture accurately the actual behavior of complex materials and structures.

Originality/value

The uniqueness and importance of this structure leads to an intensive study of its structural behavior. Ambient vibration tests are carried out under environmental excitation. Extraction of modal parameters is obtained from output-only experimental data. The EFI methodology is applied for the OSP on a large-scale structure. Information coming from several length scales, from sub-micrometer dimensions to macroscopic scales, is included in the material definition. The strong differences found between the stiffness along the longitudinal and transverse directions of wood lumbers are incorporated in the structural model. A multi-scale model updating approach is carried out by means of a GA technique to calibrate the micromechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally.

Keywords

Acknowledgements

E.I. Saavedra Flores acknowledges the financial support from the Chilean National Commission for Scientific and Technological Research (CONICYT), FONDECYT REGULAR research project No. 1140245.

Citation

Castro-Triguero, R., Garcia-Macias, E., Saavedra Flores, E., Friswell, M.I. and Gallego, R. (2017), "Multi-scale model updating of a timber footbridge using experimental vibration data", Engineering Computations, Vol. 34 No. 3, pp. 754-780. https://doi.org/10.1108/EC-09-2015-0284

Publisher

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Emerald Publishing Limited Bingley, United Kingdom

Copyright © 2017, Emerald Publishing Limited

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