A Study of Temperature and Aging Effects on Eigenfrequencies of Concrete Bridges for Health Monitoring

in Engineering (2017), 9

This paper discusses the influence of environmental factors and of normal material aging on the eigenfrequencies of concrete bridges based on monitoring data registered during 4 years of a specific bridge ... [more ▼]

This paper discusses the influence of environmental factors and of normal material aging on the eigenfrequencies of concrete bridges based on monitoring data registered during 4 years of a specific bridge. It is a new composite steel-concrete bridge built in 2006 in Luxembourg. The measurements are analyzed and compared to literature data. The final objective is the use of real monitored eigenfrequencies for structural health monitoring and damage detection based on identification of stiffness losses in practical applications. Therefore, it is very important to identify and compensate for outdoor influences namely temperature, excitation force level and normal aging effects, like creep and shrinkage of concrete and their impact on material properties. The present paper aims at describing these effects in order to separate them from damage effects. It is shown that temperature change rates and temperature gradients within the bridge have an influence on the eigenfrequencies. Hence the key idea for assessment from the full database is to select only measurements with small temperature differences and slow temperature change rates. [less ▲]

A signal processing method to remove environmental effects for damage detection in bridge structures

Poster (2014, July)

This paper consists in damage diagnosis for several real bridges in Luxembourg. Before, different analysis methods were applied to the data measured from these structures showing interesting results ... [more ▼]

This paper consists in damage diagnosis for several real bridges in Luxembourg. Before, different analysis methods were applied to the data measured from these structures showing interesting results. However, some difficulties are faced, especially due to environmental influences (temperature and soil-behaviour variations) which overlaid the structural changes caused by damage or confuse damage levels. These environmental effects are investigated in detail and removed in this work through Principal Component Analysis. Damage index is based on outlier analysis [less ▲]

Some conclusions from the measurements of temperatures and their gradients on eigenfrequencies of bridges

Scientific Conference (2014, June 30)

The ambient air temperature and solar radiation are affecting the soil and asphalts’ stiffness and hence the eigenfrequencies of a bridge. Very often eigenfrequencies are automatically determined by ... [more ▼]

The ambient air temperature and solar radiation are affecting the soil and asphalts’ stiffness and hence the eigenfrequencies of a bridge. Very often eigenfrequencies are automatically determined by special algorithms from structural response data generated by ambient excitation and measured by permanently installed sensors that is sometimes called “output only analysis” or “operating modal analysis”. Additionally the ambient air temperature is registered and finally the eigenfrequencies are analyzed versus the air temperature. The graph is normally a scatter diagram and each point is one measurement. In general the eigenfrequencies decrease with increasing temperature, whereas often linear regression is used to determine the line of best fit. But the slope of this straight line and the width of the scatter around the regression line differ from bridge to bridge. Especially this scatter field around the mean value at a determined temperature complicates the detection of damage, which is also often based on eigenfrequencies’ reduction. Hence the difficulty among others consists in separating damage from environmental effects. [less ▲]

Proceedings of IMAC XXXII Dynamics of Coupled Structures

in Firkret, Necati Catbas (Ed.) Damage Detection in Civil Engineering Structure Considering Temperature Effect (2014, February)

This paper concerns damage identification of a bridge located in Luxembourg. Vibration responses were captured from measurable and adjustable harmonic swept sine excitation and hammer impact. Different ... [more ▼]

This paper concerns damage identification of a bridge located in Luxembourg. Vibration responses were captured from measurable and adjustable harmonic swept sine excitation and hammer impact. Different analysis methods were applied to the data measured from the structure showing interesting results. However, some difficulties arise, especially due to environmental influences (temperature and soil-behaviour variations) which overlay the structural changes caused by damage. These environmental effects are investigated in detail in this work. First, the modal parameters are identified from the response data. In the next step, they are statistically collected and processed through Principal Component Analysis (PCA) and Kernel PCA. Damage indexes are based on outlier analysis. [less ▲]

DETECTION AND LOCALISATION OF DAMAGE ON INDUSTRIALLY PRODUCED CONCRETE SLABS THROUGH TIME- AND FREQUENCY-DOMAIN APPROACHES

in Carrera, E.; Miglioretti, F; Petrolo, M. (Eds.) 6th ECCOMAS Thematic Conference on Smart Structures and Materials (SMART2013), Torino 24-26 June 2013 (2013, June)

The objective of this work is to address the problem of damage detection in civil engineering structures using non-destructive techniques and dynamic measurements. To this purpose, time- or frequency ... [more ▼]

The objective of this work is to address the problem of damage detection in civil engineering structures using non-destructive techniques and dynamic measurements. To this purpose, time- or frequency-domain methods are used for the diagnostics. It consists in practical output-only techniques as Stochastic Subspace Identification (SSI) for modal identification or Enhanced Principal Component Analysis (EPCA) for detecting the presence of damage. The use of the Hankel matrix instead of the observation matrix improves effectively the robustness of these methods. Damage localization is based on Frequency Response Functions (FRFs) and sensitivity analysis of PCA results. The efficiency of the above-mentioned methods has been demonstrated in earlier studies mainly on numerical examples and small-scale laboratory experiments. It was also tested successfully on industrial examples to perform machine condition monitoring using a reduced set of sensors. In this work, the investigation is performed on precast prestressed and non-prestressed concrete slabs. Successive damages were artificially introduced in the slabs by loading heavy weights and by cutting steel wires, which induced cracks in the structure. The examples show the consequences of the considered techniques for damage identification. The results that are very different between prestressed and non-prestressed slabs may be used as input for the condition control of this kind of structures. [less ▲]

Dynamische Methoden zur Schadensidentifikation an einer kontinuierlich geschädigten vorgespannten Zweifeldbrücke

in VDI-Berichte 2160 (2012)

Static and dynamic testing on prestressed concrete slab elements with artificial bond deficiencies

in Proceedings of the 4th Bond in Concrete Conference, Vol. 1: General Aspects of Bond (2012)

Dynamic damage identification using linear and nonlinear testing methods on a two-span prestressed concrete bridge

in Proceedings of the Third International Symposium on Life-Cycle Civil Engineering, IALCCE’12 (2012)

Schadensidentifikation an Stahl- und Spannbetonplatten anhand von linearen und nichtlinearen Schwingungsanalysen

in Schwingungsüberwachung VDI Konferenz (2011)

Dynamische Zustandsbewertung einer Verbunsbrücke: Beobachtung äußerer und nichtlinearer Einflüsse auf die modalen Eigenschaften

in Beton- und Stahlbetonbau (2010)