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Eingeladener Vortrag
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Practical applications of recent BAM-research results of NDT and monitoring in civil engineering
(2018)
Nondestructive testing and monitoring was of mayor interest in BAM-research related to the survey of civil engineering structures during the last two decades. Three case studies about research projects carried out at BAM were presented. All three projects focussed on the survey of parameters and safety related tasks in bridge engineering and inspection. First, the monitoring of the Berlin main station was presented with focus on the sensors developed specifically for this project. The second case study presented and application of guided ultrasonic waves to CFRP-strengthened bridges. The method was sucsessully applied to two of four different strengthening measures carried out min. 10 years ago. The last project presented the feasibility study of a network consisting of simple Bluetooth modules to survey changes in the moisture content in sand and massive concrete.
The book chapter first analyses the history of higher education in Europe. Second step describes the current Bologna process. Finally, the rule of the Bundesanstalt für Materialforschung und -Prüfung (BAM) in supporting PhD-students during their research and preparation of theire theses in cooperation with Universities is described
Current measurement methods for dertermination of moisture analyse near-surface moisture distribution. During an externally funded research project, microwaves in the Bluetooth(R) frequency band width were utilized for Setting-up a module network. Without additional sensors, the feasibility study confirmed that threedimensional data can collected to obtain a threedimensional data set as basis for the estimation of moisture distribution inside massive building materials.
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.
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- and long-term monitoring aiming at 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 aim of the modelling is the derivation of a damping equation for the formal model to determine the moisture damping exponent to finding a correlation.
Active thermography
(2017)
Active thermography is introduced as tool for diagnostics in civil engineering structures. Aside from basic information, examples for applications of active thermography in different types of structures was presented. Active thermography was applied in historic structures to reveal former components or even ancient openings. Other examples present active thermography as a tool for nondestructive detection of debonding in CFRP strengthened structures. The way is explained, how the system was optimized for different materials.
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.
The Berlin Main Station was built between 2000 and 2006. At the occasion of the 10th anniversary after the Berlin Main Station was officially opened to train traffic, a view back on eight years of monitoring was given. For the period of the construction with different load cases, the monitoring system was required by the Railway Authorities (Eisenbahnbundesam, EBA) to survey differential vertical displacements between neighbouring supports of the glas roof and the partially prestressed middle bridges. 128 sensors were installed.The data was published in the Internet with access restricted to the BAM scientists and the owner of the station, the German Railways DB AG.
Civil engineers, who are involved in nondestructive testing have to solve an essential task: the transfer of the results of NDT-research into practice. NDT in civil Engineering is a quite new discipline. The results must meet the needs of the infrastructure owners to convince them about the usefulness of NDT. The issue of reliability of the NDT-data was discussed.
The amount of new knowledge about bridges, materials they are made of, deterioration processes for the different materials, resulting defects, methods for early detection of them and related causes for damage increases day by day. Often the knowledge remains in the heads of ageing specialists leaving the inspection teams or universities. This paper presents a feasibility study about application of a new tool from artificial intelligence to model and organize bridge engineering knowledge from a domain expert´s view. Exemplarily, knowledge and not only data from bridge testing in the field and in the laboratory were formalized for the presentation of the functionality of ontologies.