Multi-Scale Model Updating of a Timber Footbridge using Experimental Vibration Data

R Castro-Triguero (University of Cordoba, Spain), E Garcia-Macias (University of Seville, Spain), EI Saavedra Flores (Universidad de Santiago de Chile, Chile), MI Friswell (Swansea University) & R Gallego (University of Granada, Spain)

Engineering Computations, Vol. 34, No. 3, 2017, pp. 754-780


Purpose - The purpose of this paper is to capture the actual structural behaviour 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.This approach offers a first structural model in which optimal sensor placement (OSP) methodologies are applied in order to improve the system identification process. In particular, the Effective Independence (EFI) method is employed 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. In order to improve the accuracy of our numerical predictions, the material response is modeled by means of a homogenisation-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 micro-mechanical 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 our updated numerical simulations and the corresponding experimental measurements. The longitudinal and trans- verse 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 behaviour 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 are 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 micro-mechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally.

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This material has been published in Engineering Computations, Vol. 34, No. 3, 2017, pp. 754-780, the only definitive repository of the content that has been certified and accepted after peer review. Copyright and all rights therein are retained by Emerald.

Link to paper using doi: 10.1108/EC-09-2015-0284

Engineering Computations