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- Non-destructive testing (4)
- Concrete (3)
- Debonding (2)
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Organisationseinheit der BAM
The research project "Ultrasonic Net for Concrete Monitoring (UNeCOM)" aims at developing a methodology for an embedded ultrasonic network for the condition assessment of infrastructure constructions. Civil engineering structures made of concrete, which are located in tectonically active regions or undergo special loading conditions, may require continuous monitoring. It is important to assess the condition of the building and its stability to recognise and classify the effect of a seismic event or evolving damage at early stages before failure occurs. Embedded ultrasonic sensors offer the possibility to detect changes in the material and degradation mechanisms from inside the structure in areas which are difficult or impossible to inspect otherwise. In contrast to conventional ultrasonic testing methods, where the concrete surfaces are scanned with ultrasound probes, this new approach uses sensors, which are embedded into concrete, eliminating the effect of variable coupling conditions between sensors and concrete. This method allows an integral detection of changes in the concrete structure, for example due to seismic activities, to detect mechanical impacts, as well as degradation of the material due to overloading. Such methods have great relevance especially for the monitoring of constructions like power plants, bridges, offshore structures and other structures with high technical safety requirements. The sensor network can be controlled remotely through the internet which is also being used for data transfer. The embedded sensor network is designed to monitor structural damage and concrete degradation globally with high sensitivity.
Structural health monitoring contributes to early damage detection in the built infrastructure. During the last two decades, the sensor networks transferred from wired to wireless sensor networks.
Several methods exist to measure moisture in building materials. Most of the introduced commercial humidity measurement methods as provide information about the local or near surface moisture. A feasibility study is presented to demonstrate, how the Received Signal Strength Indicator (RSSI) of a BlueTooth® Low Energy (BLE) signal, transmitted from the BLE-module embedded in building materials with changing moisture content. The BLE-module communicates with a mobile Smart Device as tablet or mobile phone. The RSSI indicates to what extend the received signal strength is changed due to moisture, while the transmitted signal strength remains constant.
The presented development of a damping model is a research component of an experimental feasibility study about moisture in building materials measured with Bluetooth® Low Energy (BLE) signals. This study may be part of a structural health monitoring aiming on early damage detection in the built infrastructure and is increasingly focusing on wireless sensor Network technology. It is investigated, how the Received Signal Strength Indicator (RSSI) of a BLE signal, transmitted from the BLE-module embedded in building materials with changing moisture content is damped. The BLE-module communicates with a mobile Smart Device as tablet or mobile phone via 2.45 GHz-ISMfrequency band where water dipoles start to oscillate. If the BLE-signal transfers through a moist material, the moisture Content influences the RSS-Indicator. The damping model demonstrates this damping effect on RSSI by the abstraction of the reality observed in a real system.
Assessment of existing steel structures - A guideline for estimation of the remaining fatigue life
(2007)
Within the presented research project, experimental and numerical investigations were performed to develop a thin-shelled, modular, mobile element system made of a micro-reinforced ultra-high-performance ductile concrete (DUCON®). Material parameters were experimentally determined to adapt the material model within the numerical analysis applying the Drucker-Prager relationship. Afterwards, for validation of the numerical models, quasi-static and high-velocity impact tests were performed on plate-like structures. Finally, a suitable geometry of transportable barrier elements will be designed, which provides a maximum of resistance against impact by a minimum of weight and a maximum of mobility.
Monitoring accelerated corrosion in chloride contaminated concrete with ground penetrating radar
(2012)
In this research, laboratory experiments were carried out to investigate the feasibility of using ground penetrating radar (GPR) for corrosion detection and/or monitoring, and the mechanism of corrosion caused GPR signal changes, taking into account the influence of several parameters: Chloride, rebar size and cover depth. With the understanding of the mechanism, a novel method for detecting reinforcement corrosion in concrete with GPR is proposed, together with a series of signal processing toolkits for corrosion visualization and image comparison.