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- Rheology (2)
- Structural health monitoring (2)
- Aqueous phase of cement paste (1)
- BOFDA (1)
- Braking performance (1)
- Brillouin optical frequency-domain analysis (1)
- Cement (1)
- Concrete (1)
- Damage detection (1)
- Distributed Brillouin Sensing (1)
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- 7 Bauwerkssicherheit (3)
- 3 Gefahrgutumschließungen; Energiespeicher (2)
- 3.2 Gefahrguttanks und Unfallmechanik (2)
- 7.4 Baustofftechnologie (2)
- 8 Zerstörungsfreie Prüfung (2)
- 8.6 Faseroptische Sensorik (2)
- 5 Werkstofftechnik (1)
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- 6 Materialchemie (1)
- 6.6 Physik und chemische Analytik der Polymere (1)
The paper presents rheometric results and hydration curves for cementitious systems based on cement mixed with different aqueous phases at solid volume fraction of = 0.45. The varied aqueous phases were deionized water, limewater, the filter residue of a cement paste mixed at w/c = 2.0, and the filtrate of cement paste at solid volume fraction of 0.45. Each cementitious system provided different amounts and sizes of particles formed in the aqueous phase. The pastes were observed with and without polycarboxylate ether based superplasticizer. It was observed that the presence of particles causes higher PCE saturation dosages to achieve a minimum value, but the minimum value is only affected in the case of large particles. In all cases with and without PCE, the presence of small particles causes increased plastic viscosity. In addition, with decreased number and size of hydrates in the aqueous phase the hydration was retarded, which was specifically pronounced in the presence of PCE
The safety of any transport system depends on a multitude of conditions, parameters and circumstances. In this regard, the interaction of the carried Cargo with the carrying vehicle represents a factor influencing the overall safety of any transport. The effects of cargo on the vehicle have to do with the vibration or shifting of the cargo, affecting the lateral stability of the vehicles and the braking performance.
Such interaction has been associated to road crashes and maritime vehicles capsizing. Simulation of cargo-vehicle interaction thus represents an interesting Topic when a reduction in transport accidents is pursued. In this paper, the fundamentals principles for simulating the interaction of the liquid cargo and the carrying vehicle, is presented. In the case of a road transportation, the proposed simplified Simulation methodologies, show good agreement with a full-scale test.
This chapter gives an overview about polymer optical fiber (POF) sensors with the focus on structural and civil engineering applications. POF properties such as the high-strain range, the low Young’s modulus, and specific scattering effects open new fields for fiber-optic sensing applications. POF properties, sensitivities, and cross-sensitivities that are relevant for sensing are introduced. Advantages and limitations are discussed. State-of-the-art POF sensors and application examples are presented in subsections with regard to their underlying measurement principles.
Effective assessment and management of railway infrastructure for competitiveness and sustainability
(2018)
In this chapter the challenges facing railways have been illustrated through the description of two important events occurring in different geographical areas. While the explosion in Quebec, Canada, points out the importance of taking away the transportation infrastructure from highly populated areas; the disruption of the European railway network in Rastatt, Germany, describes the importance of designing alternative routes to critical railway segments, together with the need to have contingency plans to face extraordinary situations regarding the connectivity in a given transport network.
Future research efforts are recognized in relation with the railway car – track interaction, as the dynamic loads derived from such interaction could be reducing the life of such infrastructure. It is particularly important for infrastructures dedicated to the transportation of liquid hazardous substances.
Automatic vibration-based structural health monitoring has been recognized as a useful alternative or addition to visual inspections or local non-destructive testing performed manually. It is, in particular, suitable for mechanical and aeronautical structures as well as on civil structures, including cultural heritage sites. The main challenge is to provide a robust damage diagnosis from the recorded vibration measurements, for which statistical signal processing methods are required. In this chapter, a damage detection method is presented that compares vibration measurements from the current system to a reference state in a hypothesis test, where data9
related uncertainties are taken into account. The computation of the test statistic on new measurements is straightforward and does not require a separate modal identification. The performance of the method is firstly shown on a steel frame structure in a laboratory experiment. Secondly, the application on real measurements on S101 Bridge is shown during a progressive damage test, where damage was successfully detected for different damage scenarios.
The substantial progresses in fiber-optic communications in combination with the increasing economic and political interest in structural health monitoring have led to a commercial establishment of distributed Brillouin sensing. The sensor systems, mainly based on the time-domain techniques, have been successfully implemented in the areas such as pipeline leak detection, geohazard effects, and ground movement detection.
This chapter introduces a further advancement in the area of Brillouin sensing in the frequency domain. The so-called Brillouin optical frequency-domain analysis (BOFDA) offers crucial perspectives in terms of dynamic range and cost efficiency.
The main principle of the frequency-domain approach takes advantage of the reversibility between the time and frequency domain given by a Fourier transform in the analysis of linear systems. The hereby presented overview gives a summary of the benefits and challenges of frequency-domain measurements closely tied to the narrowband recording of the complex transfer function. This function relates the counterpropagating pump and probe laser light along the sensor fiber providing the pulse response of the measurement system by applying the inverse Fourier transform (IFT). The strain or temperature distribution can be then determined from the retrieved Brillouin frequency shift (BFS) profile along the fiber.
In order to observe the effect of the aggregate phases between 2 mm and 16 mm without overlap with rheological effects induced by the cement hy-dration and without interactions with a threshold fine sand particle size that affects both, paste and aggregates, rheological experiments were conducted on a limestone filler based paste mixed with aggregates up to 16 mm. Vari-ous aggregate fractions were blended and mixed with the replacement paste in different volumetric ratios.
The dry aggregates’ flow coefficients were determined and compared to yield stress and plastic viscosity values at different aggregate volume fractions. The results indicated that the flow coefficient is not a suitable parameter to predict the performance of the aggregates in the paste. It was shown that the yield stress of pastes is largely determined by the blend of different aggregate fractions, while the plastic viscosity to large extend depends upon the coars-est aggregate fraction.
Based on the results, ideal aggregate composition ranges for minimised yield stress are presented. For the plastic viscosity no such grading curves to achieve minimum values could be found, but high viscosity curves are identified.