Split cylindrical specimen after performing the RCM test under load. The chloride penetration front is lightly discoloured by indicator liquid. The area with cracking shows higher penetration depths.
Before a new structure is built, it must first be meticulously planned and designed. In the process, proof must also be provided that the structure will remain load-bearing and serviceable over its entire service life. To provide this proof, the verification concepts usually assume that the structures maintain their ideal condition after construction for the entire service life. In reality, however, the building materials used age and change their condition, which means that the properties of the structures as a whole also change over the course of their useful life. The reliability and quality of the structures decrease as a result and, in addition, the load-bearing safety and safety in use may even be impaired. The process of "change of state" in the ageing of building materials and supporting structures can have chemical or physical causes depending on the type of building material, such as wood, steel, concrete, and the exposure, and takes place on different spatial and temporal scales, such as from micro-cracks in steel to spalling on concrete. In the worst case, the impairment of load-bearing and service safety due to the age-related change in condition can result in catastrophic accidents. A tragic example of such an accident from the recent past is the collapse of the Morandi Bridge in Genoa in 2018. Apart from such catastrophic accidents, infrastructure structures, such as railway or motorway bridges, are becoming increasingly important for our daily lives and also our economy. At present, for example, the converted monetary value of the transport infrastructure alone in Germany is around €1,000 billion. It is therefore not surprising that the quality and also the environmental compatibility and sustainability of structures as well as the economic management of infrastructure structures are becoming increasingly important at all decision-making levels of the national economy. In order to be able to prevent catastrophic accidents in the future and even increase the service life of structures, it is important to learn more about the description, evaluation and prognosis of the future load-bearing and service safety of a structure through research.
A Research Training Group (RTG) funded by the German Research Foundation (DFG) is a research network in which various research institutions are usually involved and conduct topic-specific research in cooperation. The special feature of this research programme is that Research Training Groups offer university graduates an optimal environment for a doctorate through regular exchange, various further training measures and interdisciplinary supervision.
In the DFG-funded Research Training Group "Models for the Description of the Change of State during the Ageing of Building Materials and Supporting Structures", the various chemical and physical effects on the structures are first examined. These include, for example, high force effects due to storm gusts, frequently recurring loads such as car traffic over a bridge, strong temperature fluctuations or the effects of road salt or seawater on reinforced concrete. The phenomenon of ageing and the processes contributing to the change in condition are to be investigated both experimentally in laboratories and test halls and numerically by means of computer-aided simulations within the framework of the research network. From the knowledge gained, models are then to be developed in individual cases that allow a forecast of the change in condition and quality in the future. The prognosis models should not depict the various physical and chemical processes separately from each other, since in reality the various influences from inside and outside do not act in isolation, but rather together in the majority of cases. In order to develop prognosis models that are as close to reality as possible and enable a coherent statement about the serviceability of a structure, the interaction of the processes should therefore also be recorded. Furthermore, in contrast to currently existing models, the identified mechanisms are to be investigated and described on different spatial and temporal scales of the material structure, i.e. from nanometres to areas visible to the naked eye and from relatively short time units to years. Once the results on smaller scales have been validated by experiments, they can be used to develop the first simplifying engineering models for an application of the results at the structural level.
A more detailed description of the research project, the individual members and their research focus, dissertations already completed within the framework of the Graduate School 2075 and other interesting information can be found on the website of the Graduate School 2075.
Urbanisation is a worldwide phenomenon and improving air quality in urban areas is a prerequisite for an adequate quality of life. Many studies have shown that particulate matter in the air is of particular concern because it is the cause of various health problems. In order to reduce particulate matter pollution, there have been extensive discussions and decisions on the part of politicians to close individual roads within cities to motor vehicles in order to reduce the particulate matter problem.
The effectiveness of such measures is fundamentally unknown, and measurement campaigns are correspondingly time-consuming and cost-intensive. Numerical simulation offers a useful approach to estimate the potential success of the measures. The quality of the numerical results depends on several factors and parameters.
Overview of city district in Basel incl. wind directions and highlight on barrier road
While we have already been able to validate the flow solver for wind speed profiles developed at our institute [1], a traffic simulator based on the Nagel-Schreckenberg model was implemented in the course of a Bachelor thesis [2], which models the traffic in the streets of this urban quarter in a time-dependent manner. The neighbourhood is a densely built-up inner city area, which has an extension of approx. 500 x 500 m. The individual vehicles collide with each other depending on the driving conditions. The individual vehicles emit an individually weighted amount of particulate matter depending on the driving situation. The combination of this time- and vehicle-dependent generation of particulate matter and different wind situations provides a good overview of the influence that the measures discussed by politicians can have. For this purpose, a total of 4 hours of real time was simulated in combination with three different wind situations. In this way, the typical rush hour in the morning hours (06:00 - 10:00) was examined as an example.
[1] S. Lenz, M. Schönherr, M. Geier, M. Krafczyk, A. Pasquali, A. Christen and M. Giometto: Towards real-time simulation of turbulent air flow over a resolved urban canopy using the cumulant lattice Boltzmann method on a GPGPU, Journal of Wind Engineering and Industrial Aerodynamics, Vol. 189, pp. 151-162, 2019.
[2] "Development and integration of a Nagel-Schreckenberg model into a CFD solver for the simulation of pollutant dispersion in urban environments", Anna Wellmann, Bachelor thesis, 2019
