References of "De Roeck, Guido"
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See detailHealth Monitoring based on Dynamic Flexibility matrix: Theoretical Models versus in-situ Tests
Schommer, Sebastian UL; Mahowald, Jean; Nguyen, Viet Ha UL et al

in Engineering (2017), 09(02), 37-67

The paper focuses on damage detection of civil engineering structures and especially on concrete bridges. A method for structural health monitoring based on vibrational measurements is presented and ... [more ▼]

The paper focuses on damage detection of civil engineering structures and especially on concrete bridges. A method for structural health monitoring based on vibrational measurements is presented and discussed. Experimentally identified modal parameters (eigenfrequencies, mode shapes and modal masses) of bridge structures are used to calculate the inverse stiffness matrix, the so-called flexibility matrix. By monitoring of the stiffness matrix, damage can easily be detected, quantified and localized by tracking changes of its individual elements. However, based on dynamic field measurements, the acquisition of the flexibility matrix instead of the stiffness matrix is often the only choice and hence more relevant for practice. But the flexibility-based quantification and localisation of damage are often possible but more difficult, as it depends on the type of support and the location of the damage. These issues are discussed and synthetized, that is an originality of this paper and is believed useful for engineers in the damage detection of different bridge structures. First the theoretical background is briefly repeated prior to the illustration of the differences between stiffness and flexibility matrix on analytical and numerical examples. Then the flexibility-based detection is demonstrated on two true bridges with real-time measurement data and the results are promising. [less ▲]

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See detailDamage assessment of concrete structures through dynamic testing methods. Part 2: Bridge tests
Maas, Stefan UL; Zürbes, Arno; Waldmann, Danièle UL et al

in Engineerig Structures (2012), 34

The present paper is split into two parts: in the first part the different dynamic damage indicators are defined and applied to beam and slab structures under laboratory conditions, whereas the present ... [more ▼]

The present paper is split into two parts: in the first part the different dynamic damage indicators are defined and applied to beam and slab structures under laboratory conditions, whereas the present second part deals with experiments carried out on two real post-tensioned bridges. The damage indicators defined in part one are based on swept sine excitation and esveal the drop of the eigenfrequencies, the changes in damping, the varying dependency range of the first eigenfrequency on excitation force amplitude and the occurrence of higher harmonics, which changed the Total Harmonic Distorsion (THD) and a special transfer-function called TF or FRFsmall. In the first part it was proved that the amount of nonlinearities varies with damage and that harmonic excitation is favorable for good test conditions. In the laboratory this can easily be done using an electric or hydraulic shaker, but on real bridges this kind of excitation becomes more complicated due to the higher forces and the necessity to provide counter bearing for any shaker system. That is why two machines were designed and used to excite big structures harmonically, e.g. real bridges in this part. The different indicators are applied to assess the state of two post-tensioned bridges, which had been in good order and condition before artificial damage in multiple steps was caused. It turns out that the decrease in the eigenfrequencies is the most important damage indicator, provided temperature and mass dependant effects can be eliminated. All other indicators may be used as supplements to give correct tendencies, but no strict limits. [less ▲]

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See detailDamage assessment of concrete structures through dynamic testing methods. Part 1 - Laboartory Test
Maas, Stefan UL; Zürbes, Arno; Waldmann, Danièle UL et al

in Journal of Engineering Structures (2012), 34

The present paper is split into two parts: Part 1 is about laboratory tests whereas the second part deals with experiments on real bridges. This article aims at summarizing several experimental dynamic ... [more ▼]

The present paper is split into two parts: Part 1 is about laboratory tests whereas the second part deals with experiments on real bridges. This article aims at summarizing several experimental dynamic testing methods with different damage indicators to evaluate the state of prestressed as well as of passively reinforced concrete structures. First the differences between prestressed and passively reinforced concrete are repeated for static behavior, before the transition to dynamics is made. As it will be proved in the following that the amount of nonlinearities increases with damage, harmonic excitation is favorable to realize good testing conditions. It is applied to visualize variations in linear as well as in non-linear structural characteristics, which are subsequently used as damage indicators, e.g. the drop of the eigenfrequencies, the changes in damping and modeshapes, the occurrence of higher harmonics and a varying dependency of the eigenfrequency on excitation force amplitude. These different indicators will be used on passively reinforced beam elements and industrially produced prestressed slabs in the first part and on two real post-tensioned bridges in the second part. All these structures were in good order and condition before artificial damage was applied in multiple steps and the sensitivity of each damage indicator was analyzed. [less ▲]

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See detailAmbient Vibration and Forced Excitation Tests of a Composite Bridge: Environmental influences and nonlinear effects on the dynamic properties
Bungard, Volker UL; Mahowald, Jean UL; Waldmann, Danièle UL et al

in Proceedings of the International Conference on Noise and Vibration Engineering, ISMA (2010)

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See detailComparison of linear and nonlinear static and dynamic behaviour of prestressed and non-prestressed concrete slab elements
Mahowald, Jean UL; Bungard, Volker UL; Maas, Stefan UL et al

in Proceedings of the International Conference of Noise and Vibration Engineering (2010)

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See detailDamage assessment of a gradually damaged pre-stressed concrete bridge using static load tests and non-linear vibration characteristic
Waltering, Markus UL; Bungard, Volker UL; Maas, Stefan UL et al

in International Conference on Noise and Vibration Engineering (2008)

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See detailNon-destructive Damage Assessment Using Non-linear Vibration
Waltering, Markus UL; Bungard, Volker UL; Maas, Stefan UL et al

in International Modal Analysis Conference, IMAC-XXVI (2008)

Detailed reference viewed: 62 (16 UL)