Potential of the Deformation Area Difference (DAD)-Method for Condition Assessment of Bridge Structures

Scientific Conference (2019, August 27)

The construction industry ranks in the back rows in terms of digitalization. The numerous existing bridge structures require considerable effort for inspection and reliable assessment of their condition ... [more ▼]

The construction industry ranks in the back rows in terms of digitalization. The numerous existing bridge structures require considerable effort for inspection and reliable assessment of their condition. However, the state-of-the-art for inspecting these structures still relies on the visual inspection realized by bridge inspectors. The current paper summarizes several research projects in the field of condition assessment of bridge structures at the University of Luxembourg by analysing the structural response due to dynamic excitation and static loading tests. The latest development aims at using the most modern measurement techniques by combining them to a new method, the Deformation Area Difference (DAD)-Method in order to simplify and automatize at most the inspection process. The proposed DAD-Method is based on conventional static load deflection tests. It allows the localization of stiffness-reducing damage by using a very precise measurement of the deflection line and by combining this outcome to the deflection line generated by a simplified finite element model of the bridge. In order to investigate the condition of a bridge by the DAD-Method modern measurement techniques such as photogrammetry and laser scanning are used. In the framework of the conducted research, these techniques are also compared to traditional measurement systems such as total station and inductive displacement sensors as well as to digital levelling sensors. By theoretical examples and experimental tests, it can be shown that the DAD-Method is able to detect and localize damage when the damage level is dominant on the measurement noise. This paper investigates also the application of the method on a real bridge structure in Luxembourg. All of the above-mentioned measurement techniques were used, whereby the photogrammetry is applied using both, stable tripods and an autonomous flying drone. This allows examining the accuracy of the different measurement systems when applied on a real-size structure. [less ▲]

Static load deflection experiment on a beam for damage detection using the Deformation Area Difference Method

Scientific Conference (2018, October)

A reliable and safety infrastructure for both transport and traffic is becoming increasingly important today. The condition assessment of bridges remains difficult and new methods must be found to provide ... [more ▼]

A reliable and safety infrastructure for both transport and traffic is becoming increasingly important today. The condition assessment of bridges remains difficult and new methods must be found to provide reliable information. A meaningful in-situ assessment of bridges requires very detailed investigations which cannot be guaranteed by commonly used methods. It is known that the structural response to external loading is influenced by local damages. However, the detection of local damage depends on many factors such as environmental effects (e.g. temperature), construction layer (e.g. asphalt) and accuracy of the structural response measurement. Within the paper, a new so-called Deformation Area Difference (DAD) Method is presented. The DAD method is based on a load deflection experiment and does not require a reference measurement of initial condition. Therefore, the DAD method can be applied on existing bridges. Moreover, the DAD method uses the most modern technologies such as high precision measurement techniques and attempts to combine digital photogrammetry with drone applications. The DAD method uses information given in the curvature course from a theoretical model of the structure and compares it to real measurements. The paper shows results from a laboratory load-deflection experiment with a steel beam which has been gradually damaged at distinct positions. The load size is chosen so that the maximum deflection does not exceed the serviceability limit state. With the data obtained by the laboratory experiment, the damage degree, which can still be detected by the DAD method, is described. Furthermore, the influence of measurement accuracy on damage detection is discussed. [less ▲]

Krümmungsbasierte Methode zur lokalen Schadensdetektion von Brückenkonstruktionen

Presentation (2017, September)

Condition assessment and damage localisation for bridges by use of the Deformation Area Difference Method (DAD-Method)

in Performance-based approaches for concrete structures (2016, November)

Already today, a huge number of bridges are in an ailing condition due to their increasing age and due to an increased traffic volume, especially of heavy transport vehicles. To assess their load bearing ... [more ▼]

Already today, a huge number of bridges are in an ailing condition due to their increasing age and due to an increased traffic volume, especially of heavy transport vehicles. To assess their load bearing capacity and subsequently predict their remaining life span, every bridge needs to be analysed by con-dition assessment. The consequences of unreliable condition assessment should not be underestimated, as most bridge constructions constitute cost intensive and indispensable infrastructures. Thus, modern condition assessment methods, easy and obvious in their application, are needed in order to reduce future investigations. To offer an easy handling alternative to evaluate the condition of bridges, the Deformation Area Dif-ference Method has been developed. Hereby, the accruing deformation of bridges under a static load will be analysed with the help of modern measurement equipment. Therefore, the resulting defor-mation curves like the deflection, the inclination angle and the curvature curves, will be analysed in one diagram together with the results out of initial measurements or theoretically calculated defor-mation curves. The DAD-Method is then applied on the surface difference area between those two curves for the deflection, the inclination and the curvature. It will be demonstrated that a localisation of damage is possible, independent from the degree of damage. In this study, the applicability of the DAD-Method including the comparison of innovative measure-ment techniques using a laboratory specimen is investigated. For further explanation of the back-ground of the DAD-Method, the results from a FE-calculation are presented. [less ▲]

Investigation of temperature-dependent stiffness variation of a layer of asphalt and their possible effect on the deformation behaviour of concrete structures

in 6th International Conference on Experimental Vibration Analysis for Civil Engineering Structures, Duebendorf 2015 (2015, October)

In the time of increasing maintenance costs, the continuous inspection and the earliest possible damage detection become more and more important. In order to minimize future maintenance costs, the exact ... [more ▼]

In the time of increasing maintenance costs, the continuous inspection and the earliest possible damage detection become more and more important. In order to minimize future maintenance costs, the exact evaluation of the condition of the structure and the exact assessment of potential damages are of essential importance. Therefore the University of Luxembourg carries out projects to investigate an efficient application of different assessment methods taking into account praxis relevant test conditions. As a part of this project especially the changing temperatures which influence the stiffness of the materials are analysed. As a consequence, for the condition assessment of structures, the asphalt layer cannot only be taken into consideration as a mass applied as load on the structure. Due to bond effects of the asphalt layer to the load carrying element its changing stiffness induced by changing temperatures influences the stiffness of the whole structure. Within this paper this effect will be illustrated. First the load carrying behaviour and the stiffness of pre-stressed concrete slabs realized with and without an additional asphalt layer will be investigated in a climate chamber and the results will be compared for different temperatures. [less ▲]