Open Access

Engineering structures are an important part of our transport infrastructure. Their failure is associated with high safety risks and economic damage. Ensuring the availability of these constructions and guaranteeing their operational safety are thus important tasks. Currently, maintenance of engineering structures is a reactive process and therefore not yet a predictive process. Every 3 to 6 years, the structures are visually inspected, all damages are documented and a condition grade is assigned to the structure based on the detected damages. Continuous data-providing methods such as monitoring are used only very occasionally. With the help of monitoring, condition data about the structures are continuously collected, which can be used for a better assessment of the structures. On the one hand, this would increase safety of engineering structures, and on the other hand, it makes the shift towards predictive maintenance management based on real-time data and predictions, where the onset of damage is detected before it occurs, possible in the first place. Monitoring plays therefore an important role in the management of the infrastructure. It is a crucial a step towards the digitalisation of our infrastructure and existing processes. Although there are many use cases for monitoring that have already been successfully implemented, monitoring is not yet widely used by German road authorities due to several challenges that were also identified within the scope of the project. Therefore, a guide has been developed in which the current obstacles related to monitoring are identified and possibilities for integrating monitoring into existing processes are offered. To ensure optimal alignment with the needs of road authorities, both an online survey and a workshop have been conducted. The results are summarised in a brochure that is made available to authorities to improve the use of monitoring in Germany. This paper presents the guideline and the brochure.

The Nibelungen Bridge in Worms, Germany has been selected as a national demonstration structure for advanced non-destructive testing (NDT) and structural health monitoring concepts to extend the lifetime of civil structures and to optimize O&M actions. Parts of the research that involves this bridge as a demonstrator belong to the focus area program SPP100+. In this program, the bridges SHM System has been extended and combined with an additional setup of vibration sensors. The used digital smart sensor with pre-processing functions, the arrangement of the sensors at the structure and additional edge computing capability allows the investigation of transfer learning and other methods directly into the real structure. The living lab with seven triaxial accelerometers can be reconfigured in real-time and adjusted to the needs of AI models for classification. The comparison with the existing conventional SHM sensors has been made possible by hardware synchronization to the existing SHM System and collocating sensors at similar positions, so that a hardware exchange can be an investigated use-case for the transfer learning. During idle times, the system collects vibration data like a conventional SHM system.

In this investigation, we present a direct method employing UV-light radiation to induce point defects, specifically Ti3+ and VO, onto the surface of TiO2 nanosheets (TiO2-NSs) and efficiently decorate them with Pt particles. The addition of the Pt precursor is carried out during rest periods following UV-light cessation (light-induced samples, LI) and during UV-light exposure (photo-deposited samples, PD). The size and distribution of Pt particles on both LI and PD TiO2-NSs are systematically correlated with varying resting times, enabling precise control over Pt loading. The characterization of various TiO2-NSs is extensively conducted using microscopy techniques (FESEM, TEM, and HAADF-STEM) and spectroscopy (XPS). Gas chromatography is also employed for the evaluation of the H2 photocatalytic performance of various samples. Our findings reveal that Pt particles deposit on the TiO2-NSs surfaces as nanoparticles under illumination. After a 5 minutes resting time, a combination of Pt single atoms (SAs) and clusters, with a maximum loading of 0.37 at%, is formed. Extending the resting time to 60 minutes results in a gradual reduction in Pt SAs and clusters, leading to the deposition of Pt nanoparticles with lower loadings. Notably, Pt SAs and clusters exhibit superior performance in hydrogen evolution, showcasing a remarkable 4000-fold increase over pristine TiO2-NSs. Additionally, sustained UV radiation during Pt addition in the photo-deposited samples results in the formation of Pt nanoparticles with lower loading compared to LI samples, consequently diminishing photocatalytic hydrogen production. This study not only provides insights into the controlled manipulation of Pt SAs on TiO2-NSs but also highlights their exceptional efficacy in hydrogen evolution, offering valuable contributions to the design of efficient photocatalytic systems for sustainable hydrogen generation.

The low-temperature plasma (LTP) probe is a common plasma-based source used for ambient desorption–ionization mass spectrometry (MS). While the LTP probe has been characterized in detail with MS, relatively few studies have used optical spectroscopy. In this paper, two-dimensional (2D) imaging at selected wavelengths is used to visualize important species in the LTP plasma jet. First, 2D steady-state images of the LTP plume for N2+ (391.2 nm), He I (706.5 nm), and N2 (337.1 nm) emissions were recorded under selected plasma conditions. Second, time-resolved 2D emission maps of radiative species in the LTP plasma jet were recorded through the use of a 200 ns detection gate and varying gate delays with respect to the LTP trigger pulse. Emission from He I, N2+, and N2 in the plasma jet region was found to show a transient behavior (often referred to as plasma bullets) lasting only a few microseconds. The N2+ and He I maps were highly correlated in spatial and temporal structure. Further, emission from N2 showed two maxima in time, one before and one after the maximum emission for N2+ and He I, due to an initial electronic excitation wave and ion–electron recombination, respectively. Third, the interaction of the LTP probe with a sample substrate and an electrically grounded metallic needle was studied. Emission from a fluorophore on the sample substrate showed an initial photon-induced excitation from plasma-generated photons followed by electronic excitation by other plasma species. The presence of a grounded needle near the plasma jet significantly extended the plasma jet lifetime and also generated a long-lived corona discharge on the needle. The effect of LTP operating parameters on emission spectra was correlated with mass-spectral results including reagent-ion signals. Lastly, five movies provide a side-by-side comparison of the temporal behavior of emitting species and insights into the interactions of the emission clouds with a sample surface as well as an external needle. Temporally and spatially resolved imaging provided insights into important processes in the LTP plasma jet, which will help improve analyte ion sampling in LTP–MS.

The resonances of railway bridges have often been analysed for short bridges under periodical high-speed trains, for simply supported one-span bridges, for the fundamental bridge mode, and by time-domain analyses. Many time-consuming calculations have been performed to establish simplified rules for standards. In this contribution, the passage of different (existing, new and hypothetic) trains over different (simply supported, integral, multi-span, continuous) bridges will be analysed in frequency domain by using three separated spectra with the purpose to get a better physical insight in the phenomena. At first, the excitation spectrum of the modal forces is built by the mode shape and the passage time of the train over the bridge. The second spectrum is the frequency response function of the bridge which include the modal frequency, damping and mass. The third part is the spectrum of the axle sequence of an arbitrary train which is not limited to periodical or specific (conventional, articulated, regular or standard) trains and which does not include any bridge parameters. The final solution in frequency domain is obtained as the product of these three complex, strongly varying spectra for the dominating bridge mode or in general as the sum of these products over all relevant bridge modes. The time domain solution is obtained via the inverse Fourier transform, and the resulting time histories have been successfully compared with some measurement results. The method is applied to the vertical and torsional modes of a mid-long single-span bridge on elastomeric bearings under standard train speeds, to a short two-span bridge under high-speed traffic, and to a long three-span integral bridge under long periodical freight trains. Different resonance and cancellation effects have been found for systematically varied train speeds according to the axle sequence of the whole train which is dominated by the two locomotives in that case. To be more specific, the first torsional mode of the mid-span bridge is excited for a train speed of 100 km/h whereas the second bending mode is excited for a train speed of 160 km/h. In both cases, the other mode is suppressed by the minima of the axle-distance spectra. In addition, the case of the German high-speed train ICE4, a Maglev train on a viaduct, and the very high-speed hyperloop case will be discussed briefly. In general, it is shown that resonance effects are also worth to be studied for freight and passenger trains with lower speeds.