Damage assessment of concrete structures through dynamic testing methods. Part 1 - Laboartory Test

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 ▲]

Influence of environmental changes on modal characteristics

in Federation for Structural Concrete (fib) (2011)

Condition assessment of concrete structures and bridges using vibration monitoring in comparison to changes in their static properties

Doctoral thesis (2010)

The thesis deals with the non-destructive condition assessment of civil engineering structures made of reinforced and prestressed concrete as well as bridges and concentrates on a comparison of static and ... [more ▼]

The thesis deals with the non-destructive condition assessment of civil engineering structures made of reinforced and prestressed concrete as well as bridges and concentrates on a comparison of static and dynamic investigation methods. The main questions discuss the sensitivity of changes in static as well as in dynamic properties during the mechanical lifetime of those types of structures under laboratory conditions, the sensitivity of these changes when testing in-situ and the dimension of undesired environmental influences on the dynamic properties. Therefore, a gradually loaded laboratory reinforced concrete beam (cp. chapter 7) and a reinforced as well as a prestressed concrete slab (cp. chapter 8) are investigated for changes in their static and dynamic parameters until reaching their ultimate loads. Furthermore, a successively damaged and stepwise loaded laboratory reinforced concrete slab and a prestressed concrete slab (cp. also chapter 8) are under investigation and also compared in changes in their static as well as in dynamic properties during their lifetimes. By means of static and dynamic tests on a successively damaged and stepwise loaded prestressed concrete bridge (cp. chapter 9) it was possible to investigate the amount of changes in static and dynamic properties for a real in-situ object. A long-term measurement of a composite bridge (cp. chapter 10) demonstrates the environmental influences on the static and dynamic properties of a system which have to be considered when conducting comparative non-destructive condition assessment techniques on real objects. All tests are calculated respectively simulated by the method of the integration of stress (cp. chapter 6) or the finite element method by using the softwares ANSYS and SOFISTIK. Furthermore, measured eigenfrequencies and modeshapes are used to adapt finite element models with the aim to improve the model or to locate and quantify damaged areas. The work is a contribution to the application of non-destructive static and dynamic condition assessment methods on civil engineering structures made of concrete in the sector of civil engineering. [less ▲]

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

in Beton- und Stahlbetonbau (2010)

Statische und dynamische Zustandsbewertung von Stahlbetonbauteilen

in Abstract book of 51. Forschungskolloquium des Deutschen Ausschusses für Stahlbetonbau (2010)

Non-destructive damage assessment of constructions in civil engineering using non-linear vibration characteristics.

in Concrete 21st Century Superhero (2009)

Non-destructive Damage Assessment Using Non-linear Vibration

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

Structural Health Monitoring of a Composite Bridge

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