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Paper des Monats
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A long-term study was conducted on double-lap spruce wood-concrete joints to investigate their shear strength and stiffness over a 12-month period. These joints were manufactured using both wet and dry processes, each incorporating two adhesive types for bonding the wood to the concrete: a brittle epoxy and a ductile polyurethane (PUR). The experimental design exposed the joints to three specific long-term environments: (1) outdoor exposure, (2) indoor conditions with applied load, and (3) outdoor conditions with applied load. The wood concrete joints exposed to outdoor conditions were subjected to destructive shear testing at intervals of 0 (serving as the reference sample), 2, 4, 6, and 12 months, respectively. For joints subjected to both indoor and outdoor conditions with shear loading, the shear deformation of joints was monitored continuously over the 12 months before performing the destructive tests. A gradual reduction in the shear stiffness and strength of dry joints (produced using the dry bond method) exposed to outdoor conditions was observed over a 12-month period, primarily due to bond failure at the concrete-adhesive interface. The wet joints exhibited no degradation in shear stiffness and strength across long-term conditions over the same period. The bond failure observed in dry joints was predominantly associated with stresses arising from dimensional changes in the wood. No degradation was found in the cross-linking density of the adhesive or in the concrete’s compressive stiffness and strength.
Protection against terrorist or accidental scenarios in industrial settings requires suitable designs of structures to resist blast loads. Field testing as well as finite element simulations are among the techniques available to engineers in the understanding of the structural behavior against blast loading. As blast testing of complex scenarios can be very resource intensive, tests are generally performed for simplified scenarios. Numerical tools can be used to model these scenarios in order to get a better insight into blast loading, structural response and the resulting damage to the structure. In the next steps, the simplified scenario is successively modified in numerical simulations to incorporate complexities that cannot be covered in blast testing experiments. One of the conditions for this approach to work is that the original simplified numerical simulation is valid. The scopes and challenges encountered in such a validation are the focus of this presentation. A relatively ‘simple’ field test of a horizontal reinforced concrete (RC) slab subjected to blast loading is taken as an example for validation of the performance of numerical tools. The blast test incorporated various measurement techniques to quantify the blast load as well as the behavior of the RC slab. Blast load was measured using flush-mounted piezoelectric pressure gauges, whereas acceleration sensors and fiber-optic sensor cables were used to characterize the dynamic behavior of the slab under blast loading. Additionally, damage characteristics were ascertained also using fiber-optic sensing. The application of such measurement techniques, along with different numerical software available for the analysis of the scenario in question,
demonstrate the scope of our contribution.
A combination of neutron time-of-flight and neutron backscattering spectroscopy was used to investigate the molecular dynamics of Janus polynorbornenes (Janus poly(tricyclononenes)) on a microscopic level.
These Janus polynorbornenes, denoted as PTCNSiOR, have a semirigid backbone with −Si(OR)3 side groups attached to it. R represents the length of the alkyl side chain. Here side chain lengths of R = 3 (propyl) and R = 8 (octyl) were considered. It is worth mentioning that these polymers have some potential as active layers in gas separation membranes, especially for the separation of higher hydrocarbons. The combination of time-of-flight and backscattering will ensure a reasonably broad time window for analysis where the incoherent intermediate scattering function SInc(q,t) is considered. Previously, it was shown by X-ray investigations that the system undergoes a nanophase separation into alkyl side chain-rich domains surrounded by a backbone-rich matrix. For PTCNSiOPr (R = 3), the alkyl side-chain-rich domains are truly isolated in the backbone-rich matrix, whereas for PTCNSiOOc (R = 8) these domains percolate through the matrix. Further, it was also previously shown that the alkyl side-chain-rich domains undergo a glass transition. The advantage of neutron scattering experiments discussed here is that besides temporal also spatial information is obtained which will allow conclusions to be drawn about the type of molecular fluctuations. At the lowest measured temperature, the decay in Sinc(q,t) is due to the methyl group rotation. The methyl group dynamics is analyzed in terms of a modified jump-diffusion in a 3-fold potential and yields to a reasonable fraction of hydrogens which contribute to the methyl group rotation. At higher temperatures, the decay in SInc(q,t) is due to both the methyl group rotation and the segmental dynamics in the alkyl side-chain-rich domains. The segmental diffusion is modeled by a sublinear diffusion. For the analysis of the scattering function SInc(q,t) of PTCNSiOPr an elastic scattering due to the immobilized backbone-rich matrix must be taken into account. The analysis reveals that the segmental dynamics is confined by the finite size of alkyl chain-rich domains and that it is intrinsically heterogeneous in nature. Both effects are more pronounced for PTCNSiOPr in comparison to those of PTCNSiOOc.
Characteristics of environmental stress cracking of PE-HD induced by biodiesel and diesel fuels
(2024)
In the context of the increasing effect of carbon dioxide emissions on the global climate biodiesel produced from renewable sources has emerged as a promising contender replacing fossil fuels, especially in long-range transport vehicles, using existing engines and infrastructure.
High-density polyethylene is one of the prevailing materials for pipe and container applications for storage and transport of such fuels, both, from fossil and renewable resources. The contact with the respective fuels raises questions concerning material compatibility as biodiesel exhibits significant differences compared to conventional diesel fuel affecting its sorption and plasticization behavior in polyethylene. In this study, its behavior with respect to environmental stress cracking, considered one of the most frequent damage mechanisms leading to failure of polymer parts and packaging, was evaluated using the well-established Full Notch Creep Test. This
approach allows for a detailed fracture surface analysis using imaging techniques, such as optical and laser scanning microscopy, as well as infrared spectroscopy. Comparing the environmental stress cracking behavior in standard surfactant solutions with that in biodiesel and diesel, respective crack propagation rates, showing different levels of acceleration, were determined and details of the underlying mechanisms could be revealed.
Furthermore, the specific infrared absorption of the biodiesel’s ester functionality allows its semi-quantitative determination on the fracture surface of the tested specimens after failure. Thus, a preferred uptake of sorptive fluids in the fracture zone due to local morphological changes of the polyethylene could be directly evidenced by infrared spectroscopy.
The integration of advanced simulation models into industrial applications, especially in civil engineering, is a challenge that requires to develop new concepts. In particular, this is related to the validation of models using open access and FAIR data as well as objective methods for identifying model parameters and model comparison with the integration of both the models and their calibration into reproducible workflow systems.
The challenges are illustratively discussed for a variety of applications ranging from bridge monitoring over the structural behavior under blast loading up to the additive manufacturing of concrete. An important basis for model validation is the existence of machine-readable data structures for experimental data, e.g. based on semantic representations. In addition, platforms to share this structured data in a searchable format in addition with reproducible scientific workflows must be established.
Based on these tools, objective methods for model parameter estimation and validation of the models are a critical step in ensuring their accuracy and usefulness in industrial applications. Bayesian inference is one approach that can be used to optimize simulation parameters, improving the accuracy of the model while being able to estimate the uncertainty. Integrating these procedures in a real-time application with a bidirectional information exchange between the physical systems and the virtual simulation model leads to the concept of digital twins.
For complex simulation models, the computational efficiency is a significant barrier both for real-time applications and in the context of model calibration with potentially millions of required forward-model evaluations. As a consequence, reduced order modeling approaches such as the proper generalized decomposition method can be used to build an efficient to evaluate model - speeding up the online computation but requiring a precomputation in an offline phase.
Finally, a perspective for integrating material and structural design into a joint design optimization is given. The integration of advanced simulation models into industrial applications is a rapidly evolving field with significant potential for innovation and progress. From additive manufacturing of concrete to digital twins and reduced order modeling, there are many tools and approaches that can be used to improve industrial processes and drive progress in a variety of industries.
Innovation and scientific progress are often located in the synthesis of new flame retardants or in the compounding of new composites. Thus, although nearly everyone applies fire tests to ascertain the flame retardancy achieved, regular, cost-efficient fire testing is preferred, sometimes its reliability and meaningfulness are questioned. The goal of this revised chapter is to inspire the exploitation of the potential of fire testing beyond a soulless pass-and-fail or isolated number rating. Recommendations are given as to how fire behaviour can be investigated and how data can be evaluated faithfully and meaningfully. Backgrounds and benchmarks are discussed as thought-provoking impulses which could allow bench-scale fire testing to be exploited as a vital basis and powerful tool for science-based development.
Applying synergistic multicomponent systems is often key to efficient flame retardancy. Different flame retardants are combined or used together with fillers, adjuvants, or synergists to enhance their efficiency, reduce the worsening of other properties, or reduce the costs. Further, fibres and other reinforcing fillers contribute to fire properties crucially. Although the main flame-retardant modes of action are known, the scientific understanding usually falls short, when it comes to complex multicomponent systems, the crucial tiny optimizations, or quantifying in terms of specific fire properties. This book chapter illuminates the need for the multicomponent approach, the concept of synergistic flame retardants, and the main phenomena. Multicomponent systems are discussed in their capacity as general powerful strategy for achieving and optimizing future flame retardant polymeric materials.
This book presents the proceedings of the Thirteenth International Conference Structures in Fire. The conference took place at the Department of Civil Engineering, University of Coimbra, Portugal, from 19 to 21 June 2024, under the auspices of the SIF movement. Structural fire safety is a crucial aspect of the design of buildings and infrastructures. Significant advances in research have increased the knowledge on this topic. However, until the 1990s, there were few forums for structural fire engineers to exchange ideas and share research findings. SIF (Structures in Fire) specialised workshop series was conceived in the late 1990s and the “First International SIF Workshop” was held in Copenhagen, Denmark in 2000, followed by workshops in Christchurch, New Zealand (2002), Ottawa, Canada (2004) and Aveiro, Portugal (2006). The series of workshops evolved into conferences and the 2008 event in Singapore was the fifth International Conference on Structures in Fire. This was followed by events in East Lansing, USA (2010), Zurich, Switzerland (2012), Shanghai, China (2014), New Jersey, USA (2016), Belfast, UK (2018), Brisbane, Australia (2020) and Hong Kong, China (2022). Information about previous conferences, including complete proceedings, can be found at www.structuresinfire.com. The main mission of SIF conferences is to provide an opportunity for researchers and engineers from the global structural fire engineering community to participate, share and discuss the recent findings, innovations and developments with their peers in an open and international forum. Following the great success of the previous International Conferences, the University of Coimbra was selected to host the 13th International Conference on Structures in Fire. As with most of the recent conferences, the number of papers submitted far exceeds the number of papers that can be accommodated in the three-day programme, even with two parallel sessions. SIF 2024 received 249 abstracts before the deadline and accepted 172 abstracts after the review process by at least three reviewers from the scientific committee. These proceedings represent 132 full papers, collectively representing the state of the art in fundamental knowledge and practical application of structures in fire. Forty-two countries from around the globe have contributed to them. The papers are grouped into the following research topics: Applications of Structural Fire Engineering, Composite Structures in Fire, Concrete Structures in Fire, Timber Structures in Fire, Masonry Structures in Fire, Steel Structures in Fire, Experimental Research of Structures in Fire, Numerical Modelling of Structures in Fire, Other Topics Related to Structures in Fire. Finally, the Organizing Committee would like to thank the continuous support from the SIF Steering Committee chaired by Prof Jean-Marc Franssen. We also would like to thank to the Scientific Committee chaired by Prof Paulo Vila Real, the authors and all the supporting staff (and volunteer team) from the Institute for Sustainability and Innovation in Structural Engineering (ISISE) in Coimbra, for making SIF 2024 a successful conference.
Fire-induced spalling of normal strength concrete with different types of blended Portland cement
(2024)
The cement industry is looking to reduce its overall CO2 footprint. Greener manufacturing can be achieved by the introduction of more clinker-reduced cements. Concrete exposed to fire tends to show explosive spalling caused by thermomechanical and thermohydraulic processes. It is therefore essential to determine how concretes with clinker-reduced cements behave under fire exposure, especially for concretes containing calcined clays, as these are expected to be the supplementary cementitious material of the future.
In this paper, normal strength concretes with four different cements (CEM I, CEM II/A-LL, CEM III/A and CEM II/B-Q) were examined for their fire-induced spalling behaviour. In addition, a mix with PP fibres was investigated for each concrete. The experiments were conducted on ring-restrained cylindrical specimens exposed to the hydrocarbon fire curve. The results showed that the cement type influences spalling behaviour. Samples with CEM I spalled the least, followed by CEM II/A-LL and CEM III/A.
Finally, samples with CEM II/B-Q showed the most severe damage. It was found that the spalling behaviour of different concretes correlates with the moisture content before exposure to fire, meaning that higher moisture content leads to higher spalling susceptibility. The use of 2 kg/m³ PP fibres completely inhibited spalling regardless of the cement type used and therefore remains a successful avoidance strategy.
This paper presents an experimental study on the hydraulic failure of a submerged layer of cemented soil stressed by a localized upward water flow. Different mixtures of glass beads bonded with solid paraffin bridges were used as artificial material for the cemented granular soil. Variations in the cementation strength of the material were carefully introduced with different particle sizes and binder contents. The hydraulic fracture tests were then carried out with an upward flow injected at a controlled rate through a small section at the bottom of the samples. From a phenomenological perspective, the results reveal the existence of at least three modes of failure for a cemented soil layer: (1) overall block uplift, (2) block rupture by median crack at the inflow zone, and (3) progressive excavation of a fluidized path along the walls. The critical flow rate and pressure drop conditions at failure have been carefully quantified for the different mixtures and layer thicknesses, leading to a fair estimation of the hydraulic resistance of the samples, which here is found to be virtually independent of the grain size. However, the test results also showed inconsistent failure modes precluding so far the derivation of a simple phase diagram. Nevertheless, it was possible to rationalize all the measured data by employing appropriate modifications of the classical dimensionless numbers that describe the fluidization of purely frictional materials, whereby the cementation strength of the soil is quantified at the microscale through the yield tensile force of the intergranular bonds. Irrespective of its subsequent development, during which boundary conditions obviously play a major role, the initiation of the instability appears to take place very locally at the inlet when the drag force induced by the flow overcomes the cementation strength of the paraffin bonds. The results of this study thus appear to endorse the extension of the dimensional relationships of particulate systems in interaction with fluid flows to the case of cemented granular materials, in a similar vein as in recent previous studies.
Considering the existing challenges involved in the transfer of flame retardant (FR) formulations from epoxy (EP) resins to glass fiber reinforced composites (GFRCs), obtaining data on the post-fire flexural properties of such composites is even more challenging as this involves balancing test parameters with potential composite delamination. In this study, solvent-free FR additives: ammonium polyphosphate (APP), and inorganic silicate (InSi) were added at 10, 30% and 50% w/w loading to a Bisphenol A diglycidyl ether (DGEBA)-dicyandiamide (DICY)-Urone resin matrix. These resin formulations were transferred to bidirectional (BD) glass fiber composites via prepregs. A novel, but facile approach was developed to prepare the composite samples for furnace tests at 400 oC. The composites were also subjected to fire exposure at different heat fluxes and times via a bench-scale test and subsequently tested via three-point bending. At approximately 3.5% P content, the FRs significantly improve the fire performance of both the resins and composites. However, they also degrade the systems’ pre- and postfire flexural modulus and strength. Therefore, improving the flame-retardant mode of action of the FRs in the composites, contrastingly reduces their structural integrity post-fire leading to a trade-off effect.
Considering the existing challenges involved in the transfer of flame retardant (FR) formulations from epoxy (EP) resins to glass fiber reinforced composites (GFRCs), obtaining data on the post-fire flexural properties of such composites is even more challenging as this involves balancing test parameters with potential composite delamination. In this study, solvent-free FR additives: ammonium polyphosphate (APP), and inorganic silicate (InSi) were added at 10, 30% and 50% w/w loading to a Bisphenol A diglycidyl ether (DGEBA)-dicyandiamide (DICY)-Urone resin matrix. These resin formulations were transferred to bidirectional (BD) glass fiber composites via prepregs. A novel, but facile approach was developed to prepare the composite samples for furnace tests at 400 oC. The composites were also subjected to fire exposure at different heat fluxes and times via a bench-scale test and subsequently tested via three-point bending. At approximately 3.5% P content, the FRs significantly improve the fire performance of both the resins and composites. However, they also degrade the systems’ pre- and postfire flexural modulus and strength. Therefore, improving the flame-retardant mode of action of the FRs in the composites, contrastingly reduces their structural integrity post-fire leading to a trade-off effect.
The residual post-fire mechanical properties of fiber-reinforced epoxy (EP) composites are influenced by their fire residues after burning. This study uses intumescent/low-melting glass flame retardants (FRs) to tailor fire residues in epoxy resin. Processibility of prepregs, and their quality are analysed for transfer of the flame-retardant epoxy resins to layered glass-fiber reinforced composites (GFRCs). Minimal effects were found on the pre-fire flexural strengths of the composites due to low loading of the FRs. However, when transferred to GFRCS, the fire residues diminish significantly. Process, testing, and material adaptations are required to improve theoretical and experimental estimations of the post-fire mechanics of the composites.
Structural Health Monitoring (SHM) wird zunehmend zur kontinuierlichen Zustandsbewertung von Ingenieurbauwerken eingesetzt. Wichtige Bewertungsparameter sind globale Systemeigenschaften, wie z. B. Eigenfrequenzen, zu deren Bestimmung Beschleunigungssensoren eingesetzt werden. Häufig werden sog. MEMS-Sensoren (Micro Electro Mechanical Systems) verwendet, die jedoch ein hohes Rauschniveau aufweisen. Alternativ können rauschärmere IEPE-Sensoren (Integrated Electronics Piezo Electric) eingesetzt werden, die auch bei geringster Strukturanregung Schwingungen zuverlässig erfassen. Ferner besteht das Problem, dass Änderungen der Eigenfrequenzen infolge Bauwerksschädigung schwer von Änderungen der Eigenfrequenzen infolge Umwelteinflüssen zu unterscheiden sind. Letztere verändern die Eigenschaften der Struktur und die des Messsystems. Um Umwelteinflüsse auf das Messsystem im Anwendungsgebiet Ingenieurbau zu untersuchen, wurden IEPE-Beschleunigungsaufnehmer hinsichtlich ihres Übertragungsverhaltens im niederfrequenten Beschleunigungsbereich analysiert. Es zeigt sich, dass das Verhalten nicht nur frequenz-, sondern auch temperaturabhängig ist, während die Luftfeuchte keinen Einfluss hat. Diese für das Bauwerk unbedenklichen Einflüsse müssen für eine robuste Zustandsüberwachung kompensiert werden. Für die Anwendung im Ingenieurbau werden IEPE-Sensoren empfohlen, da sie ein hohes Signal-zu-Rausch-Verhältnis aufweisen und niederfrequente Bauwerksschwingungen zuverlässig erfassen.
Im Forschungsprojekt DiMoWind-Inspect wurde untersucht, welche Grundvoraussetzungen geschaffen werden müssen, um digitale Methoden für die Instandhaltung von Offshore-Windenergieanlagen einsetzen zu können. Daten aus allen Lebensphasen der Anlagen werden derzeit nur selten effizient dafür genutzt, um die sinnvollsten Instandhaltungsmaßnahmen am richtigen Ort, zum richtigen Zeitpunkt und mit den geringsten Kosten durchzuführen. Eine im Vorhaben entwickelte einheitliche Strukturierung der bisher häufig unstrukturierten Bau- und Instandhaltungsdaten ermöglicht ihre übergreifende, anwenderspezifische Verfügbarkeit. Hierfür werden Prinzipien des Referenzkennzeichnungssystems RDS-PP adaptiert. Es wird aufgezeigt, wie neben Bauteilen auch zusätzliche Informationen wie Instandhaltungsmaßnahmen oder Mängel strukturiert werden können. Dem Ansatz des Building Information Modeling folgend werden die Bauwerkskomponenten direkt mit den Informationen aus Inspektionen und weiteren Instandhaltungsmaßnahmen verknüpft. So können Informationen aus dem Betrieb über den Zustand der Struktur verarbeitet und für die maßgebenden Berechnungen und Nachweise zur Verfügung gestellt werden. Als Anwendungsfall wird ein zweistufiges Konzept vorgestellt, das zur Bewertung der Ermüdungslebensdauer eines korrosionsgeschädigten Konstruktionsdetails der Gründungsstruktur einer Offshore-Windenergieanlage mit Informationen aus der Instandhaltung eingesetzt wird.
This article presents woven carbon-fiber-reinforced polymer (CFRP) tubular mesh used as a reinforcement on the inner surface of hollow beams made of high-performance concrete (HPC). The tubular mesh was designed to serve as both the tensile and shear reinforcement of hollow beams intended for the construction of small self-supporting structures that could be assembled without mechanization. The reinforcement was prepared with a tri-axial weaving machine from carbon filament yarn and was homogenized using epoxy resin. The interaction of the composite reinforcement with the cementitious matrix was investigated, and the surface of the reinforcement was modified using silica sand and polyvinyl alcohol (PVA) fibers to improve cohesion. The sand coating enhanced bond strength, resulting in the significantly higher flexural strength of the hollow beam of 128%. The PVA fibers had a lower positive effect of 64% on the flexural strength but improved the ductility of the beam. Individual beams were connected by gluing steel parts directly inside the hollow core of the HPC beam. This procedure provides good interaction between the CFRP reinforcement and the glued steel insert and allows for the fast and simple assembly of structures. The weaving of additional layers of the CFRP reinforcement around HPC beams was also explored. A small structure made of the hollow HPC beams with inner composite reinforcement was constructed to demonstrate the possibilities of the presented technology.
Die Fourier-Transformations-Infrarotspektroskopie (FTIR-Spektroskopie) bietet eine herausragende Charakterisierungsmöglichkeit für Bitumen und bitumenhaltige Bindemittel. In Kombination mit multivariaten Analysemethoden und somit einem chemometrischen Ansatz erlaubt die FTIR-Charakterisierung Aussagen über verschiedene übergeordnete Eigenschaften, wie die Raffinerie, den Alterungszustand oder die Alterungsempfindlichkeit, eine Abschätzung verschiedener chemischer und physikalischer Kennwerte, wie z.B. den Asphaltengehalt, den Erweichungspunkt Ring und Kugel, die Nadelpenetration sowie den komplexen Schermodul und den Phasenwinkel sowie die Identifizierung verschiedener Additive wie Polymere oder Wachse.
We introduce a novel adaptive Gaussian Process Regression (GPR) methodology for efficient construction of surrogate models for Bayesian inverse problems with expensive forward model evaluations. An adaptive design strategy focuses on optimizing both the positioning and simulation accuracy of training data in order to reduce the computational cost of simulating training data without compromising the fidelity of the posterior distributions of parameters. The method interleaves a goal-oriented active learning algorithm selecting evaluation points and tolerances based on the expected impact on the Kullback-Leibler divergence of surrogated and true posterior with a Markov Chain Monte Carlo sampling of the posterior. The performance benefit of the adaptive approach is demonstrated for two simple test problems.
Nichtrostende Stähle sind in Tunnelbauwerken weitverbreitete Werkstoffe, die für Konstruktionsteile verschiedenster Art häufig verwendet werden. Von einfachen Hilfsbauteilen wie Kabelkanälen bis hin zu komplexen Konstruktionen von Schilderbrücken. Tunnel sind aus Sicht des Korrosionsschutzes sehr speziell und zählen in Mitteleuropa zu den korrosivsten atmosphärischen Umgebungsbedingungen. Grund hierfür ist die Kombination aus hoher Feuchtigkeit, Abgasen der Fahrzeuge (SO2, NOx) und dem winterlichen Streusalzeinsatz (Cl-). Die daraus entstehen-den feuchten Oberflächenfilme sind hochchloridhaltig und weisen durch Reaktionen mit Schwefeldioxid sehr niedrige pH-Werte auf. Durch die in Tunnelbauwerken gleichzeitige fehlende Abwaschung der Oberflächenfilme durch Regenereignisse können sich die Verunreinigungen an vielen Ausstattungsteilen über die Einsatzzeit aufkonzentrieren. Für metallene Bauteile und insbesondere auch für nichtrostende Stähle ist dadurch eine hohe Korrosionsbeanspruchung vorhanden, die bei der Werkstoffauswahl bzw. beim Korrosionsschutz zu berücksichtigen ist. Aufgrund der Gefahr für das Auftreten Spannungsrisskorrosion bei einigen nichtrostenden Stahlsorten in Tunnelatmosphären, sind Regeln für die Werkstoffauswahl in Tunneln aufgestellt worden, die seit vielen Jahrzehnten gültig sind. Diese Regeln waren bis 2015 national in der allgemeinen bauaufsichtlichen Zulassung Z-30.3-6 für nichtrostende Stähle festgehalten und werden seit 2015 im europäische Regelwerk DIN EN 1993 1 4 (Eurocode 3) verbindlich genormt. In den ZTV-ING für den Straßenbau wird in Abschnitt 4 auf diese Regelwerke Bezug genommen.
Die Entwicklungen des nichtrostenden Stahlmarktes in den letzten Jahren, insbesondere für den Bausektor, gehen hin zu den Duplexstählen, da diese aufgrund ihres legierungsspezifisch abgesenkten Nickelgehaltes häufig kostengünstiger als die vergleichbaren Austenite sind. Neben vorteilhaften mechanisch-technologischen Eigenschaften, wie zum Beispiel höhere Festigkeiten, weisen sie zudem auch ausgezeichnete Korrosionsbeständigkeiten auf. Hierzu wurden zahlreiche Studien und Forschungsarbeiten durchgeführt, die diese Vorteile bekräftigen konnten. In Tunnelanwendungen sind Duplexstähle bislang wenig untersucht und deren Korrosionsverhalten kann in dieser speziellen Atmosphäre daher nur bedingt eingeschätzt werden.
Das Forschungsprojekt soll diese Erkenntnislücke schließen und durch eine breit angelegte Parameterstudie Duplexstähle für Tunnelanwendungen qualifizieren. Dafür wurden die Korrosionsbedingungen in den Tunneln umfassend untersucht, die Korrosivität der Tunnelatmosphäre anhand normativer Regelwerke beschrieben und dem Korrosionszustand der Prüfkörper aus nichtrostenden Stählen gegenübergestellt.
This presentation is part of the Engineering Risk Analysis group open seminars. It aims to showcase the results of an ongoing study centered on developing a novel probabilistic methodology for 3D geotechnical site characterization. This methodology integrates data from Cone Penetration Tests (CPTs) and categorical borehole data. The presentation covers the mathematical details of the proposed Multivariate Gaussian Process model and demonstrates its application to a real geotechnical site in New Zealand.
Pressure-sensitive adhesive tapes are used in a variety of applications such as construction, aircrafts, railway vehicles, and ships, where flame retardancy is essential. Especially in these applications, phosphorus-based flame retardants are often chosen over halogenated ones due to their advantages in terms of toxicity. Although there are pressure-sensitive adhesives with phosphorus flame retardants available on the market, their flame-retardant modes of action and mechanisms are not entirely understood. This research article provides fundamental pyrolysis research of three phosphorus-based flame retardants that exhibit different mechanisms in a pressuresensitive adhesive matrix. The flame-retardants modes of action and mechanisms of a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivate, an aryl phosphate, and a self-synthesized, covalently bonded DOPO derivate (copolymerized) are investigated. The blended DOPO derivate is volatilized at rather low temperatures while the covalently bonded DOPO derivate decomposes together with the polymer matrix at the same temperature. Both DOPO derivates release PO radicals which are known for their flame inhibition. The aryl phosphate decomposes at higher temperatures, releases small amounts of aryl phosphates into the gas phase, and acts predominantly the condensed phase. The aryl phosphate acts as precursor for phosphoric acid and improves the charring of the pressure sensitive adhesive matrix. All flame retardants enhance the flammability of the adhesives depending on their individual mode of action while the covalently bonded flame retardant additionally improves the mechanical properties at elevated temperatures making it a promising future technology for pressure-sensitive adhesives.
Quantifying uncertainties in subsurface properties and stratigraphy can lead to better understanding of the ground conditions and enhance the design and assessment of geotechnical structures. Several studies have utilized Cone Penetration Test (CPT) data and employed Bayesian and Machine Learning methods to quantify the geological uncertainty, based on the Robertson’s soil classification charts and the Soil Behaviour Type Index (Ic). The incorporation of borehole data can reduce the stratigraphic uncertainty. Significant challenges can arise, however, mainly due to the intrinsic differences between field and laboratory-based soil classification systems, which can potentially lead to inconsistent soil classification. To this end, this study proposes a multivariate Gaussian Process model that utilizes site-specific data and: i) jointly models multiple categorical (USCS labels) and continuous (Ic) variables, ii) learns a (shared) spatial correlation structure and the betweenoutputs covariance, and iii) produces two types of dependent classification outputs. The results indicate that the integration of geotechnical and geological information into a unified model can provide more reliable predictions of the subsurface stratification, by allowing simultaneous interpretation of USCS and Ic profiles. Importantly, the model demonstrates the potential to integrate multiple variables of different types, aiming to contribute to the development of a methodology for joint modeling of geotechnical, geological and geophysical data.
Dieses Dokument beschreibt das Verfahren Schallemissionsanalyse zur Detektion von Spanndrahtbrüchen in Spannbetonbrücken im Rahmen einer kontinuierlichen Überwachung. Die Überwachung mit Schallemission liefert eine Aussage über die Anzahl von Spanndrahtbrüchen innerhalb des Überwachungszeitraumes und innerhalb der Reichweite der installierten Sensoren. Mit dem Verfahren können die Spanndrahtbrüche lokalisiert werden. Auf Basis einer weitgehend automatisierten Datenanalyse stehen Informationen über Drahtbrüche kurzfristig nach dem Ereignis zur Verfügung.
Der Anwendungsbereich des Dokuments umfasst Brücken- und Ingenieurbauwerke mit Spanndrähten mit sofortigem oder nachträglichem Verbund. Spannsysteme ohne Verbund fallen nicht in den Anwendungsbereich. Die beschriebenen Verfahren können auf Spannsysteme ohne Verbund übertragen werden. Mit dem Verfahren Schallemissionsanalyse ist es nicht möglich, Spanndrahtbrüche zu finden, die vor dem Beginn der Überwachung entstanden sind.
Das Dokument richtet sich an Baulastträger, Anbieter und Betreiber von Monitoringsystemen auf Basis der Schallemissionsanalyse sowie Ingenieurbüros, welche die Ergebnisse der Überwachung bewerten und Maßnahmen daraus ableiten. Es gibt Hinweise zur Planung, Ausschreibung, Installation und zum Betrieb von Monitoringsystemen zur Detektion von Spanndrahtbrüchen mit Schallemission sowie zur Überprüfung der Funktion installierter Systeme. Zur Funktionskontrolle werden Signale mit der Referenzquelle am Bauwerk ausgelöst. Diese Signale sind zu detektieren, innerhalb der vorgegebenen Genauigkeit zu
lokalisieren und die vorgegebene Alarmkette muss angestoßen werden.
Technik, Teamwork und Wirksamkeit - Ein Berufsleben als Ingenieur für die technische Sicherheit
(2024)
Der Vortrag beleuchtet verschiedene Aspekte einer ingenieurtechnischen Tätigkeit zur Gewährleistung der technischen Sicherheit. Er gibt Einblicke in die unterschiedlichen Herausforderungen und die Komplexität der Aufgabenstellungen. An Beispielen wird dargestellt, wie die Ergebnisse der Tätigkeit für die Gesellschaft wirksam werden.
The recommendation is based on the coauthors’ work organized by the RILEM TC 256-SPF ‘‘Spalling of concrete due to fire: testing and modelling’’. The Committee has defined two types of screening tests for characterization of concrete propensity to fire spalling: Material screening tests and Product screening tests. Definitions of both types of tests are given in the paper. The following recommendations apply to Material screening tests. The material screening tests described in these recommendations are a set of minimum requirements to test concrete spalling propensity (for example, the minimal specimen size). This document covers the aspects of concrete characterization, specimen geometries, storage conditions, test methods and measured parameters.
Since we are facing more extreme weathers, the occurrence
of wildfire has also increased accordingly. The EU project
TREEADS aims to adopt a holistic forest fire management
and an adaptive, collaborative governance approach based
on the deployment of a new systemic and technological
framework covering all three interconnected fire
management stages: prevention & preparedness, detection &
response, and restoration & adaptation.
As part of the task in the so-called German pilot, numerical
simulations are performed to investigate the influencing
factors for vegetation fires with fire dynamics simulator
(FDS). The characteristics of vegetation are strongly related
to the local weather and ecosystem. The investigation of the
fire behavior of vegetation must be based on the local
vegetation in Germany. Thus, the flame propagation of typical
vegetation in Germany (pine needles, oak leaves, European
beech leaves etc.) was investigated in small scale and medium
scale experiments. These results are used as validation case
studies for the further simulations.
Revolutionizing our polymer industry for adaption to a sustainable carbon circular economy has become one of today’s most demanding challenges. Exploiting renewable resources to replace fossil-fuel—based plastics with biopolymers such as poly(lactic acid) (PLA) is inevitable while using waste streams as a raw material resource at least is promising. When it comes to using PLA as technical polymer, its high flammability must be addressed by flame retardants compatible with the thermoplastic processing of PLA and its compostability. This study proposes microalgae enriched with phosphorus from wastewater (P-Algae) as an elegant way towards a kind of sustainable organophosphorus flame retardant. The concept is demonstrated by investigating the processing, pyrolysis, flammability, and fire behavior of PLA/P-Algae, while varying the P-Algae content and comparing P-Algae with four alternative bio-fillers (phosphorylated lignin, biochar, thermally treated sewage sludge, and metal phytate) with different P-contents as meaningful benchmarks.
The synergistic behavior of different silicon compounds is investigated in flame retardant biocomposites with aluminum trihydroxide (ATH) as the main flame retardant. The paper shows a new approach towards sustainable biocomposites through the implementation of thermoplastic starch (TPS), leather fibers from industrial waste streams, and non-hazardous flame retardants and synergists. In these multicomponent systems, the different components address different modes of action in the fire scenario. When ATH is partially substituted by glass frits or layered silicates, fire performance is enhanced without changing the total amount of filler in the polymer. In a biocomposite with 25 phr of fiber and 90 phr of ATH, substituting 5 phr of ATH for layered silicates increased the LOI from 31.5 vol % to 34.8 vol %, decreased the peak of heat release by 20%, and increased the UL 94 rating from V-1 to V-0.
Durch das alkalische Porenwassermilieu ist Stahl im Beton vor Korrosion geschützt. Unter ungünstigen Umgebungsbedingungen (Karbonatisierung, Chlorideintrag) kann die passive Deckschicht auf der Stahloberfläche zerstört werden. Im weiteren Verlauf können sich korrosionsbedingte Folgeschäden, wie Risse und Abplatzungen am Bauwerk ergeben. Um notwendige Sanierungsmaßnahmen sind frühzeitige und weitgehend zerstörungsfrei ermittelte Informationen über das aktuelle Korrosionsverhalten der Stahlbewehrung von großer Bedeutung. Die Potentialfeldmessung ist ein etabliertes und weit verbreitetes Verfahren zur Beurteilung des Korrosionszustandes der Bewehrung in Stahlbetonbauwerken. Mit Hilfe dieses Verfahrens können Bereiche aktiv korrodierender Bewehrung zerstörungsfrei lokalisiert werden. In der Regel kommt diese Messmethode bei der Detektion chloridinduzierter Korrosion zum Einsatz. Wie und unter welchen Randbedingungen dieses Messverfahren zielführend eingesetzt werden kann, ist im Merkblatt B 03 der dgzfp erörtert.
Electrochemical potential mapping is a recognized technique for the localization of corroding reinforcing steels. Areas of corroding reinforcement steel can be located in a non-destructive manner by means of this procedure. Half‐cell potential measurements are used in order to detect chloride‐induced corrosion. However, it is not recommended in order to assess the risk of carbonation‐induced corrosion. For this purpose, determining the carbonation depth and the concrete cover appears more appropriate. The content of this specification exclusively refers to the application of mobile, local variable reference electrodes, which are only placed on the concrete surface while measuring. The technique distinguishes itself thereby from the range of corrosion monitoring systems with stationary installed reference electrodes and sensor systems, respectively, whereby it is possible to continuously track measurements within the area of the installed electrodes. However, these methods are not dealt with in this specification.
DIN 4871
(2024)
The global plastic industry relies on fossil-based materials, presenting environmental challenges. A sustainable polymer namely poly(limonene carbonate) (PLimC), made of limonene and CO2 as two monomers from non-food sources, shows advances in various applications where additives such as flame retardants (FRs) are crucial to comply with fire safety measures.
The variety of FRs is wide, and therefore the approach involved conducting a comparative study of four different halogen-free flame retardant systems that are conventionally used in polycarbonates and polyolefins to understand which FR enhances the flame resistance of PLimC most effectively. The primary task of the project is to conduct experimental evaluations to analyze the thermal properties, flammability, and fire behavior of each system. This data will offer valuable insights towards the advancement of safer and more sustainable materials.
Infraleichtbeton zeichnet sich durch eine äußerst geringe Trockenrohdichte von maximal 800 kg/m³ aus, bei gleichzeitig ausreichender Festigkeit. Daraus resultieren geringe Wärme- und Schallleitfähigkeiten. Dies ermöglicht den Einsatz als Sichtbeton in Wandelementen ohne die Notwendigkeit einer zusätzlichen Dämmschicht.
Vielversprechend erscheint der Einsatz von Leichtgranulaten in Infraleichtbeton, um seinen ökologischen Fußabdruck zu reduzieren und somit ein energieeffizientes und zugleich nachhaltiges Bauen zu ermöglichen. Die Leichtgranulate werden in einem thermo-chemischen Prozess aus gemischtem Mauerwerkbruch hergestellt. Ihre Verwendung bietet neben der Alternative zu herkömmlichen leichten Gesteinskörnungen auch die Möglichkeit, Abfallprodukte sinnvoll zu nutzen. In diesem Artikel werden die Leichtgranulate vorgestellt, ihre Anwendung in Infraleichtbeton geprüft und mit konventionellem Blähton verglichen.
Fire-induced spalling of normal strength concrete with different types of blended Portland cement
(2024)
The cement industry is looking to reduce its overall CO2 footprint. Greener manufacturing can be achieved by the introduction of more clinker-reduced cements. Concrete exposed to fire tends to show explosive spalling caused by thermomechanical and thermohydraulic processes. It is therefore essential to determine how concretes with clinker-reduced cements behave under fire exposure, especially for concretes containing calcined clays, as these are expected to be the supplementary cementitious material of the future. In this paper, normal strength concretes with four different cements (CEM I, CEM II/A-LL, CEM III/A and CEM II/B-Q) were examined for their fire-induced spalling behaviour. In addition, a mix with PP fibres was investigated for each concrete. The experiments were conducted on ring-restrained cylindrical specimens exposed to the hydrocarbon fire curve. The results showed that the cement type influences spalling behaviour. Samples with CEM I spalled the least, followed by CEM II/A-LL and CEM III/A. Finally, samples with CEM II/B-Q showed the most severe damage. It was found that the spalling behaviour of different concretes correlates with the moisture content before exposure to fire, meaning that higher moisture content leads to higher spalling susceptibility. The use of 2 kg/m³ PP fibres completely inhibited spalling regardless of the cement type used and therefore remains a successful avoidance strategy.
Wir stellen unseren Ansatz und unsere Methodik zur Simulation von Piping-Erosion vor, welche während des Installationsprozesses von Suction Bucket Fundamenten für Offshore-Windkraftanlagen auftreten kann und ein kritisches Versagen des Installationsprozesses darstellt. Wir zeigen die Ergebnisse mehrere Simulationen und analysieren die hydrodynamischen und Kontaktkräfte, die auf das granulare Medium wirken, sowie die Druckdifferenz der flüssigen Phase. Solche Simulationen können zum besseren Verständnis von Piping-Erosion und letztendlich zu dessen Verhinderung beitragen.
The Bundesanstalt für Materialforschung und -prüfung (BAM) collaborates with TNO to develop a software framework for automated calibration of structural models based on monitoring data. The ultimate goal is to include such models in the asset management process of engineering structures. As a basis for developing the framework, a multi-span road bridge consisting of ten simply supported steel box girders was selected as a test case. Our group measured output-only vibration data from one box girder under ambient conditions. From the data, we determined eigenfrequencies and mode shapes. In parallel, we developed a preliminary structural model of the box girder for the purpose of predicting its modal properties. In this contribution, we provide an overview of the measurement campaign, the operational modal analysis, the structural modeling and qualitatively compare the identified with the predicted modes. As an outlook, we discuss the further steps in the calibration process and future applications of the calibrated model.
Managing aging engineering structures requires damage identification, capacity reassessment, and prediction of remaining service life. Data from structural health monitoring (SHM) systems can be utilized to detect and characterize potential damage. However, environmental and operational variations impair the identification of damages from SHM data. Motivated by this, we introduce a Bayesian probabilistic framework for building models and identifying damage in monitored structures subject to environmental variability. The novelty of our work lies (a) in explicitly considering the effect of environmental influences and potential structural damages in the modeling to enable more accurate damage identification and (b) in proposing a methodological workflow for model‐based structural health monitoring that leverages model class selection for model building and damage identification. The framework is applied to a progressively damaged reinforced concrete beam subject to temperature variations in a climate chamber. Based on deflections and inclinations measured during diagnostic load tests of the undamaged structure, the most appropriate modeling approach for describing the temperature‐dependent behavior of the undamaged beam is identified. In the damaged state, damage is characterized based on the identified model parameters. The location and extent of the identified damage are consistent with the cracks observed in the laboratory. A numerical study with synthetic data is used to validate the parameter identification. The known true parameters lie within the 90% highest density intervals of the posterior distributions of the model parameters, suggesting that this approach is reliable for parameter identification. Our results indicate that the proposed framework can answer the question of damage identification under environmental variations. These findings show a way forward in integrating SHM data into the management of infrastructures.
Nowadays geotechnical engineering firms have powerful software tools to extent their consult-ing business also into dynamic soil-structure interaction, which before has been restricted to a rather small community of specialized experts in this field, and they certainly do. This is par-ticularly true with respect to non-seismic sources, that is all kinds of human induced vibrations. Hence, there is a demand from clients as well as from contractors to have guidance on the re-quirements as well as the limits of numerical modelling of soil-structure interaction. From the literature as well as from relevant standards, recommendations for the numerical modelling of soil-structure interaction problems involving seismic actions are well known, e. g. ASCE/SEI 4-16. There are, however, some particularities when dealing with human-induced vibrations, which are absent in seismic analyses. For human-induced excitations very little specific guid-ance has been published in the past. A machine foundation on a homogeneous half space ex-cited by harmonic loads with excitation frequency between 4 Hz and 64 Hz has been ana-lysed by means of several commercially available software packages. Parametric studies have been performed to verify if recommendations for seismic soil-structure analyses are valid for non-seismic analyses as well. This paper provides details on the benchmark example and the most important conclusions from the undertaken parametric studies.
ISO 14837-32:2015 and DIN EN 1998-1/NA:2021 as well as prEN 1997-2:2022 allow for us-ing correlations between the results of in-situ soil penetration tests and shear wave velocity (or shear modulus) to determine soil properties to be used in dynamic analyses. While the ISO and prEN standards even provide some recommendations on specific correlations to be used, the DIN standard does not. Due to the statistical nature of such correlations their general applica-bility has to be verified. We collected data sets from test sites from Germany as well as New Zealand at which cone penetration tests (CPT) as well as seismic site investigation methods were conducted. These sites comprise sandy soils as well as clayey soils, mixed soils as well as glacial soils. We compare the results of several correlations between CPT results and shear wave velocity. The accuracy of such correlations is assessed with respect to the accuracy of seismic in-situ tests. It turns out that for clean sands such correlations between CPT and Vs have a similar order of variability as seismic in-situ tests conducted at the same site. The higher the fines portion of the soil, the higher the variability of the statistical correlations, and conse-quently the less the general applicability. For glacial soils and other special soil types usage of statistical correlations to determine dynamic soil properties is not recommended.
Ausgehend von den Grundlagen der Korrosion stellt der Vortrag die Möglichkeiten des Korrosionsschutzes mit Zink vor. Dabei wird sowohl auf den kathodische Korrosionsschutz mit aktiven Zink-Anoden, als auch auf den Korrosionsschutz durch Deckschichtbildung an Zink und Zinküberzügen eingegangen. Veränderte Umweltbedingungen in Europa in den letzten Jahrzehnten, ermöglichen mit Schichtdicken um 80 µm einen Korrosionsschutz von über 100 Jahren, wenn konstruktive Randbedingungen beachtet werden.
The systematic transfer of solvent-free, additive flame retardant (FR) formulations from epoxy resins to glass fiber-reinforced epoxy composites (GFRECs) through prepregs is difficult. Additionally, obtaining data on their post-fire mechanics is often challenging. Utilizing melamine polyphosphate (MPP), ammonium polyphosphate (APP), and silane-coated ammonium polyphosphate (SiAPP) FRs with low-melting inorganic silicates (InSi) in an 8:2 proportion and 10% loading by weight in a diglycidyl ether of bisphenol A (DGEBA) resin, a systematic investigation of the processing properties, room-temperature mechanics, and temperature-based mechanics of the systems was performed. The resin was cured with a dicyandiamide hardener (DICY) and a urone accelerator. The results revealed no substantial impact of these FRs at the current loading on the resin's glass transition temperature or processability. However, the fire residues from cone calorimetry tests of the composites containing FRs were found to be only 15-20% of the thickness of the resins, implying a suppression of intumescence upon transfer. At room temperature, the decrease in the flexural modulus for the composites containing FRs was negligible. Exposure of the composites in a furnace at 400°C as a preliminary study before ignition tests was shown to cause significant flexural moduli reductions after 2.5 min of exposure and complete delamination after 3 min making further testing unviable. This study emphasizes the need for future research on recovering modes of action upon transfer of FR formulations from resins to composites. Based on the challenges outlined in this investigation, sample adaptation methods for post-fire analysis will be developed in a future study.
To safely dispose of nuclear waste in underground facilities, engineered barrier systems are needed to seal shafts and galleries. The material used in these barriers must be adapted to the host rock parameters. Shrinking and cracking must be avoided to provide a barrier with almost zero permeability. For repositories in salt rock environments, several types of salt concrete (SC) are possible construction materials. Within the project SealWasteSafe, we compared the behavior of an innovative alkali-activated material (AAM) with standard SC in their hydration and hardening phase. To monitor the microstructural changes within the two materials SC and AAM, acoustic emission (AE) signals have been recorded for up to ~250 days on 340-litercubic specimens. The phenomenon of AE is defined as the emission of elastic waves in materials due to the release of localized internal energy. Such energy release can be caused by the nucleation of micro-fracture, e.g., in concrete while curing or when exposed to load. The occurrence of AE events gives first rough indications of microstructural changes and potentially occurring cracking and thus, provides insights for structural health monitoring (SHM). The results show, that for the first 28 days after casting, less AE activity was detected in the AAM compared to SC. After 61 days, in the AAM material, the number of AE events exceeded those observed in the SC. However, the majority of the AE detected and located in AAM was related to surface effects, and not to microstructural changes or occurring cracks within the bulk volume. Additionally, the source location analysis indicated, that despite lower activity in SC, we observed some clustering of the events. In contrast, in AAM, the activity inside the specimen is randomly distributed over the whole volume. The monitoring results help to estimate the material’s sealing properties which are crucial to assess their applicability as sealing material for engineered barriers.
Manufacturing and Application of Lightweight Aggregates from Construction and Demolition Waste
(2024)
The objective of the REALight project is the development of a thermal process to produce lightweight aggregates in pilot scale and the implantation of a method to recover gypsum. Beside construction and demolition waste, various industrial by‐products are studied as raw materials. The raw materials have so far been unused or used in applications with lower quality requirements. To prove the performance of the lightweight aggregates, their technical properties are tested and their use in different applications is studied, e.g., for lightweight mortars as well as lightweight concretes.
The EU member states have set out ambitious long-term goals for deploying offshore wind energy. The installed offshore wind capacity is set to increase from 14.6 GW in 2021 to around 320 GW in 2050. This signifies the role of offshore wind energy as a major contributor to reaching the EU’s climate and energy goals. To ensure that the defined targets are met, a significant number of new wind farms has to be installed and existing wind farms reaching the end of their planned life need to be reused efficiently. Some of the relevant reuse alternatives are lifetime extension, repowering based on the existing support structures and repowering with new turbines.
As a basis of the decision-making regarding the reuse of existing offshore wind farm, the expected utility of each relevant option should be determined based on the associated expected rewards, costs and risks. The optimal concept maximizes the utility of the decision-maker and fulfills the existing constraints and requirements. To facilitate such a quantitative decision-making, models and methods have to be developed. In particular, models are required that enable predictions of (a) the condition and performance of the turbines and support structures and (b) the renumeration, costs and consequences of adverse events. These predictions have to consider (a) the governing uncertainties, (b) the available information from the planning, construction, installation and operating phase, (b) potential repair, retrofitting and strengthening schemes and (c) possible monitoring, inspection and maintenance regimes for the future operating phase.
Over the past years, several models, methods and tools have been developed at the Bundesanstalt für Materialforschung und -prüfung (BAM) to support the structural integrity management of offshore wind turbine substructures. These include:
(a) a prototype for reliability-based, system-wide, adaptive planning of inspections of welded steel structures in offshore wind farms,
(b) a method for monitoring and risk-informed optimization of inspection and maintenance strategies for jacket structures subject to fatigue, and
(c) a probabilistic cost model of inspection and maintenance of welded steel structures in offshore wind farms.
This contribution provides an overview on these works and discusses how they can be adapted and extended to support the decision-making regarding lifetime extensions and repowering of offshore wind farms.
A common engineering practice is to optimize the geometry of a structure by an iterative process, in which an objective function is minimized by systematically choosing the value of design variables and computing the value of the objective function many times.
However, regarding multiscale problems, this direct numerical approach is not feasible for a number of reasons.
The model has to take into account both the structural and unit cell (UC) scale, because the objective function to be minimized is a global quantity, while the parameters are related to the shape or material parameters of the UC.
In the absence of a clear separation of scales, the direct resolution of both scales in the numerical model leads to a significant increase in computational cost, which makes it impossible to repeatedly evaluate the model during the optimization process.
The main goal of this contribution is to overcome the aforementioned limitations and develop a new efficient computational framework for the optimal design of lattice structures.
To this end, parametric MOR is combined with DD methods.
The change in geometry of each UC within the lattice is modelled by introducing a transformation that maps the reference to the physical domain.
In offline simulations, suitable localized approximation spaces, that account for the change in geometry of the UC and its neighbours, are constructed using the concept of oversampling and random sampling.
These are then integrated into a dual DD framework to derive a robust and scalable solver, i.e. a fast-to-evaluate reduced order model (ROM).
The ROM is validated on the example of optimizing a concrete arc or pre-stressed multi beam structure minimizing its mass.
Revolutionizing our polymer industry for adaption to a sustainable carbon circular economy has become one of today’s most demanding challenges. Exploiting renewable resources to replace fossil-fuel—based plastics with biopolymers such as poly(lactic acid) (PLA) is inevitable while using waste streams as a raw material resource at least is promising. When it comes to using PLA as technical polymer, its high flammability must be addressed by flame retardants compatible with the thermoplastic processing of PLA and its compostability. This study proposes microalgae enriched with phosphorus from wastewater (P-Algae) as an elegant way towards a kind of sustainable organophosphorus flame retardant. The concept is demonstrated by investigating the processing, pyrolysis, flammability, and fire behavior of PLA/P-Algae, while varying the P-Algae content and comparing P-Algae with four alternative bio-fillers (phosphorylated lignin, biochar, thermally treated sewage sludge, and metal phytate) with different P-contents as meaningful benchmarks.
A damaging action of HNO3-55% only occurs in combination with its decomposition into nitrous gases, which can be caused by UV radiation. In a laboratory test, transparent HDPE jerrycans have been exposed to both UV radiation and 55 wt-% nitric acid solution at (41 ± 2)°C, for up to 20 days. For comparison, UV radiant exposure (21 days) and nitric acid exposure (up to 6 weeks) were performed separately, at nearly equal temperatures. The respective damages are compared with FTIR spectroscopy in ATR and HT-gel permeation chromatography (GPC) on a molecular level and with hydraulic internal pressure testing as a component test. For the used jerrycans, relevant oxidation can only be found after the combined exposure. The gradual increase in oxidative damage shows the good reproducibility of the lab exposure. The decomposition of nitric acid into nitrous gases by UV radiation – as well as the jerrycan oxidation – is also observed at lower HNO3 concentration (28 wt- %). Similar results are obtained after outdoor tests. Again, the damage occurs only after combined exposure, in contrast to the exposures to UV only and to HNO3 only, which were conducted in parallel. Outdoor exposures are most readily accepted as they represent possible end-use conditions. However, the reproducibility of these exposures is poor due to the large temporal variations in weather. There are also several safety risks, which is why the number of replicates remains limited. Since the outdoor and lab exposure tests show the same qualitative results, it is appropriate to conduct systematic studies in the laboratory. After 6 days of lab exposure, the oxidation damage is rated as critical, which corresponds to about 1/10 year in Central Europe, according to the UV radiant exposure. It should be noted that this amount can also occur in two sunny weeks.
Polymers of intrinsic microporosity exhibit a combination of high gas permeability and reasonable permselectivity, which makes them attractive candidates for gas separation membrane materials. The diffusional selective gas transport properties are connected to the molecular mobility of these polymers in the condensed state. Incoherent quasielastic neutron scattering was carried out on two polymers of intrinsic microporosity, PIM-EA-TB(CH3) and its demethylated counterpart PIM-EA-TB(H2), which have high Brunauer–Emmett–Teller surface area values of 1030 m2 g-1 and 836 m2 g-1, respectively. As these two polymers only differ in the presence of two methyl groups at the ethanoanthracene unit, the effect of methyl group rotation can be investigated solely. To cover a broad dynamic range, neutron time-of-flight was combined with neutron backscattering. The demethylated PIM-EA-TB(H2) exhibits a relaxation process with a weak intensity at short times. As the backbone is rigid and stiff this process was assigned to bendand-flex fluctuations. This process was also observed for the PIM-EA-TB(CH3). A further relaxation process is found for PIM-EA-TB(CH3), which is the methyl group rotation. It was analyzed by a jump-diffusion in a three-fold potential considering also the fact that only a fraction of the present hydrogens in PIM-EATB(CH3) participate in the methyl group rotation. This analysis can quantitatively describe the q dependence of the elastic incoherent structure factor. Furthermore, a relaxation time for the methyl group rotation can be extracted. A high activation energy of 35 kJ mol-1 was deduced. This high activation energy evidences a strong hindrance of the methyl group rotation in the bridged PIM-EA-TB(CH3) structure.
Steel tension members with hollow sections are used in applications such as trusses. To ensure the fire resistance, the steel must be prevented from heating up too quickly. A suitable solution is the application of intumescent coatings. However, the approval-based scope of application of these products generally does not include steel tension members with hollow section. This is mainly due to the lack of a corresponding European test and assessment standard. To investigate the characteristics to be considered when testing these structural members and assessing the contribution of the intumescent coating to the fire resistance, several mechanically loaded fire tests were carried out using a special tension test furnace. The fire tests have shown that intumescent coatings can provide a significant improvement in the fire resistance of steel tension members with hollow section. However, this specific application generally places particularly high demands on the performance of the intumescent coating. This is partly due to the four-sided fire exposure and the mainly filigree cross sections, which both result in high section factors. In addition, there is an increased crack formation due to the tensile load. As a result, the thermal protection of the tested intumescent coating on the tension members decreased compared to columns with the same section factor and fire exposure. Consequently, the presence of a mechanical load in the fire test as well as the type of loading affect the thermal protective performance of the intumescent coating and shall be considered.
Vorstellung OWA VERBATIM
(2024)
Das Risiko von Pfahlfussbeulen ist ein wesentlicher Grund für hohe Pfahlwandstärken bei Monopiles. Das Projekt VERBATIM - Verifikation des Beulnachweises und –verhaltens großer Monopiles zielte darauf ab, Beulphänomene zu untersuchen, die sich sowohl auf die plastischen Verformungen der Pfahlspitze während der Installation als auch auf das Beulen des eingebetteten Pfahls in der Nähe des Seebodens beziehen.
Auf der Basis aufwändiger Versuche wurden numerische Modelle entwickelt und validiert. Dies ermöglicht ein besseres Verständnis des Beulverhaltens, um die Wanddicke zu reduzieren, was Kosteneinsparungen bei der Stahlmenge sowie die Entwicklung sicherer und optimierter Strukturen erlaubt. Die bisherigen Designverfahren konnten die erfolgreiche Installation der Monopiles gewährleisten. Da die Größe von Monopiles jedoch stetig zunimmt, wird die Entwicklung verbesserter Designverfahren für sichere und kostengünstige Fundamente immer wichtiger.
Der Rückenwind-Vortrag gibt eine Übersicht zu den durchgeführten Untersuchungen und Ergebnissen
It is an essential requirement for all building products to ensure durability of their fire safety. Throughout the working life of products, intumescent coatings are aged by certain climatic factors. To predict a lifetime of several years, generally the behaviour of the intumescent coating is extrapolated based on accelerated artificial ageing. The established German and European procedures to assess the durability assume a working life of at least 10 years. For a longer period, additional evidence is required; yet the procedure and the specifications to justify this are not described. In addition to addressing this formal lack, from a scientific point of view it is necessary to investigate the degradation of intumescent coatings in detail and to propose a reliable test concept to assess durability for more than 10 years. This paper summarises the existing knowledge about the ageing of intumescent coatings. The results of various demanding weathering approaches are presented for two intumescent coatings tested in a joint research project. Moreover, formulations with a reduced amount of functionally relevant components were analysed to gain insight into the associated effects. Derived from these research results and knowledge, recommendations are proposed to assess the durability of intumescent coatings for more than 10 years based on a combination of verifications.
The risk of pile base buckling is a major reason for high pile wall thicknesses in monopiles. The VERBATIM project - Verification of the buckling detection and behaviour of large monopiles - aimed to investigate buckling phenomena related to both the plastic deformation of the pile tip during installation and the buckling of the embedded pile near the seabed.
Numerical models were developed and validated on the basis of extensive tests. This enables a better understanding of the buckling behaviour in order to reduce the wall thickness, which allows cost savings in the amount of steel and the development of safer and optimised structures. The previous design procedures were able to ensure the successful installation of the monopiles. However, as the size of monopiles continues to increase, the development of improved design methods for safe and cost-effective foundations is becoming increasingly important.
The presentation provides an overview of the investigations carried out and the results.
Die Zielstellung des Forschungsprojekts REALight ist die Entwicklung eines Verfahrens zur Herstellung von Leichtgranulaten auf der Grundlage der Ergebnisse des BMBF-Projekts „Aufbaukörnungen“ unter Erweiterung der Technologie, um Gips zurückzugewinnen und weitere mineralische Einsatzstoffe zu nutzen. In einem thermischen Verfahren werden mineralische Bau- und Abbruchabfälle über ein rohstoffliches Recycling, d. h. einen thermisch-chemischen Stoffumwandlungsprozess, zu leichten Gesteinskörnungen verarbeitet. Dabei werden im Bauschutt vorhandene Sulfate zersetzt. In einer anschließenden Rauchgaswäsche werden die Sulfate abgetrennt. Sie können als Ersatz für REA-Gips verwendet werden. Dies ist Voraussetzung für die Übertragung der Produkt- und Verfahrensidee in die Praxis und für den Nachweis der Sulfatabtrennung und -rückgewinnung aus gipshaltigem Inputmaterial. Es werden Untersuchungen zur Verbreiterung der Rohstoffbasis durch Einkopplung spezifischer mineralischer Stoffströme durchgeführt, die im Ergebnis zu einer Reduktion des Blähmittelbedarfs und einer Absenkung der Brenntemperatur führen sollen. Die Herstellung ausreichender Mengen Leichtgranulate für eine umfassende Charakterisierung nach Norm und die Praxiserprobung in bekannten Anwendungen und neuen Einsatzfeldern ist ein weiteres Projektziel.
The present work deals with the recently confirmed widening of the weld pool interface, known as a bulging effect, and its relevance in high power laser beam welding. A combined experimental and numerical approach is utilized to study the influence of the bulge on the hot cracking formation and the transport of alloying elements in the molten pool. A technique using a quartz glass, a direct-diode laser illumination, a high-speed camera, and two thermal imaging cameras is applied to visualize the weld pool geometry in the longitudinal section. The study examines the relevance of the bulging effect on both, partial and complete penetration, as well as for different sheet thicknesses ranging from 8 mm to 25 mm. The numerical analysis shows that the formation of a bulge region is highly dependent on the penetration depth and occurs above 10 mm penetration depth. The location of the bulge correlates strongly with the cracking location. The obtained experimental and numerical results reveal that the bulging effect increases the hot cracking susceptibility and limits the transfer of alloying elements from the top of the weld pool to the weld root.
Unter Passivität versteht man den Korrosionsschutz durch dünne, festhaftende Schichten aus Korrosionsprodukten. Für den schadensfreien Einsatz nichtrostender Stähle ergeben sich daraus zwei grundsätzliche Anforderungen.
Erstens muss sich die Passivschicht vollständig ausbilden können. Dabei sind die Oberflächenausführung, die mechanische Bearbeitung, die Elementverteilung, Ausscheidungen, die Wärmeeinbringung z.B. bei der schweißtechnischen Verarbeitung, Anlauffarben, sowie die chemische Nachbehandlung bzw. Konditionierung der Oberflächen von großer Bedeutung. Zweitens muss die Repassivierung von Defektstellen unter den Einsatzbedingungen möglich sein. Für das Repassivierungsvermögen sind die Legierungszusammensetzung, mögliche kritische Betriebszustände, prozessbedingte Besonderheiten, wie etwa Stagnationsbedingungen und Reinigungsprozesse von Bedeutung.
Although intense wildfire research has been done in the US and in Australia, it cannot be transferred directly to the situation in Europe as the local vegetation has a significant influence on the fire spread. The EU-funded project TREEADS and the so-called German pilot within the project are concentrating on wildfire in Europe. Extensive experimental research is done on local vegeta-tion in Germany and the experimental results are used to adjust the Fire Dynam-ics Simulator (FDS) to local vegetation as a fuel in the calculations. The particle model and the boundary fuel model are developed for the simulation of forest fires. Both models require the kinetic input for the dehydration, pyrolysis, and char oxidation process. This three-step simplified model describes the basic fuel combustion kinetic. Most published simulations use the default kinetic input of pine needles from FDS user manual.
To adjust the simulation to local vegetation, the corresponding kinetic parame-ters have been experimental investigated. Samples of pine needles, moss and other falling leaves were collected, air dried and grinded into powder. The TG analysis of all these samples were done under different heating rate of 5, 10 and 20K/min.
The activation energy and the corresponding pre-exponential factor were calcu-lated. The results show that fire spread depends significantly on the vegetation and comparison with small scale experiments show good agreement using the new kinetic parameters. The new model is applied to a larger scenario and will be compared to the results of large-scale experiments for further validation of the model.
Um die Ausbreitungsmechanismen von Vegetationsbränden und besonders bei Bodenbränden besser zu verstehen, wurden die Einflussfaktoren auf die Brandausbreitung näher untersucht. Da die Brandausbreitung auch in starkem Maße von der lokalen Vegetation abhängt, war eine Charakterisierung der lokalen Vegetation und der Bodenverhältnisse wichtig. Die Wetterverhältnisse spielen einerseits im Vorfeld des Brandes durch längere Dürreperioden als auch während des Brandes, z.B. durch den Windeinfluss, zusätzlich eine große Rolle.
Durch die numerische Simulation kann eine größere Variation der Einflussgrößen abgebildet werden als durch die zeitlich und finanziell begrenzten experimentellen Möglichkeiten. Für die Berechnungen wird der Fire Dynamic Simulators (FDS) mit dem Paket WFDS verwendet. Dadurch kann mit einem vereinfachten 3-Phasen-Reaktionskinetikmodell, bestehend aus Dehydrierung, Pyrolyse, Kohleoxidation, die Ausbreitung von Vegetationsbränden verschiedener Waldbodenarten untersucht werden. Es wurden dazu 6 typische Pflanzenarten und Bodenproben aus Kiefern-, Buchen und Eichenbeständen ausgewählt.
Die gesammelten Waldbodenproben wurden alle hinsichtlich des Wassergehalts, des organischen Gehalts, der Packungsdichte, der Dichte und der statistisch ermittelten Pflanzenartenverteilung charakterisiert. Das kinetische Abbrandverhalten wurde durch Thermogravimetrische Analyse (TGA) untersucht. Alle diese Daten wurden als Eingabeparameter für die Simulation verwendet. Die numerischen Simulationen werden mit Experimenten im kleinen, mittleren und Real-Maßstab validiert.
Um die Ausbreitungsmechanismen von Vegetationsbränden und besonders bei Bodenbränden besser zu verstehen, wurden die Einflussfaktoren auf die Brandausbreitung näher untersucht. Da die Brandausbreitung auch in starkem Maße von der lokalen Vegetation abhängt, war eine Charakterisierung der lokalen Vegetation und der Bodenverhältnisse wichtig. Die Wetterverhältnisse spielen einerseits im Vorfeld des Brandes durch längere Dürreperioden als auch während des Brandes, z.B. durch den Windeinfluss, zusätzlich eine große Rolle.
Durch die numerische Simulation kann eine größere Variation der Einflussgrößen abgebildet werden als durch die zeitlich und finanziell begrenzten experimentellen Möglichkeiten. Für die Berechnungen wird der Fire Dynamic Simulators (FDS) mit dem Paket WFDS verwendet. Dadurch kann mit einem vereinfachten 3-Phasen-Reaktionskinetikmodell, bestehend aus Dehydrierung, Pyrolyse, Kohleoxidation, die Ausbreitung von Vegetationsbränden verschiedener Waldbodenarten untersucht werden. Es wurden dazu 6 typische Pflanzenarten und Bodenproben aus Kiefern-, Buchen und Eichenbeständen ausgewählt.
Die gesammelten Waldbodenproben wurden alle hinsichtlich des Wassergehalts, des organischen Gehalts, der Packungsdichte, der Dichte und der statistisch ermittelten Pflanzenartenverteilung charakterisiert. Das kinetische Abbrandverhalten wurde durch Thermogravimetrische Analyse (TGA) untersucht. Alle diese Daten wurden als Eingabeparameter für die Simulation verwendet. Die numerischen Simulationen werden mit Experimenten im kleinen, mittleren und Real-Maßstab validiert.
Although intense wildfire research has been done in the US and in Australia, it cannot be transferred directly to the situation in Europe as the local vegetation has a significant influence on the fire spread. The EU-funded project TREEADS and the so-called German pilot within the project are concentrating on wildfire in Europe. Extensive experimental research is done on local vegeta-tion in Germany and the experimental results are used to adjust the Fire Dynam-ics Simulator (FDS) to local vegetation as a fuel in the calculations. The particle model and the boundary fuel model are developed for the simulation of forest fires. Both models require the kinetic input for the dehydration, pyrolysis, and char oxidation process. This three-step simplified model describes the basic fuel combustion kinetic. Most published simulations use the default kinetic input of pine needles from FDS user manual.
To adjust the simulation to local vegetation, the corresponding kinetic parame-ters have been experimental investigated. Samples of pine needles, moss and other falling leaves were collected, air dried and grinded into powder. The TG analysis of all these samples were done under different heating rate of 5, 10 and 20K/min.
The activation energy and the corresponding pre-exponential factor were calcu-lated. The results show that fire spread depends significantly on the vegetation and comparison with small scale experiments show good agreement using the new kinetic parameters. The new model is applied to a larger scenario and will be compared to the results of large-scale experiments for further validation of the model.
Lecture-like introduction in the topic. Fundamental aspects are discussed: Burning of polymers, fire risks, pyrolysis, combustion in the flame, physical chemistry of ignition, flame spread and steady state burning, flame retardancy mechanisms and groups of flame retardants, fire hazards (smoke, toxic products) and environmental concerns, fire testing.
Aspects of corrosion protection in the maritime sector– Focus of Current research of BAM for H2Mare
(2024)
Germany has set itself the task of becoming a world leader in the field of green hydrogen technologies and is promoting the transition to a hydrogen economy. The H2Mare flagship project is exploring the offshore production of green hydrogen and other power-to-X products. One of the most important goals is the safe and cost-efficient operation of offshore infrastructures, where a service life of at least 25 years is aimed at. However, the corrosive environment towards metallic materials presents challenges in marine areas. The atmosphere at one location could be affected by the distance to the sea level and does not have the same corrosivity for all exposed kinds of materials. The research of the durabilitty of different materials and corrosion protection systems by weathering campaigns and laboratory experiments aims to close this gap of knowledge. BAM‘s mandate is to make the data available to the responsible operators through standardisation to ensure safety and cost efficiency.
We present our approach and methodology for simulating piping erosion, which occurs during the installation process of suction bucket foundations for offshore wind turbines. We show several simulations and analyze the hydrodynamic and contact forces acting on the granular fabric and the differential pressure of the fluid phase. We demonstrate weak scaling performance on the LUMI supercomputer with a parallel efficiency of up to 90% for 4096 Graphics Compute Dies.
Sacrifice Few to Save Many: Fire Protective Interlayers in Carbon- Fiber-Reinforced Laminates
(2024)
The fire protection of carbon-fiber-reinforced polymer (CFRP) laminates often relies on flame-retardant coatings, but in some applications, their efficacy may diminish upon direct fire exposure due to rapid pyrolysis. This study introduces an innovative approach by integrating protective interlayers within the laminate structure to enhance the fire resistance. Various materials, including ceramic composite WHIPOX, titanium foil, poly(etherimide) (PEI) foil, basalt fibers, rubber mat, and hemp fibers, were selected as protective interlayers. These interlayers were strategically placed within the laminate layout to form a sacrificial barrier, safeguarding the integrity of the composite. Bench-scale fire resistance tests were conducted, where fire (180 kW/m2) was applied directly to the one side of the specimen by a burner while a compressive load was applied at the same time. Results indicate significant prolongation of time to failure for CFRP laminates with protective interlayers, which is up to 10 times longer. This innovative approach represents a potential advance in fire protection strategies for CFRP laminates, offering improved resilience against fire-induced structural failure.
Relation of craze to crack length during slow crack growth phenomena in high‐density polyethylene
(2024)
The craze‐crack mechanism occurring in high‐density polyethylene (HDPE) causing slow crack growth and environmental stress cracking is investigated in detail with respect to the relation of crack length and the related craze zone. This is essential for the understanding of the resulting features of the formed fracture surface and their interpretation in the context of the transition from crack propagation to ductile shear deformation. It turns out that an already formed craze zone does not inevitably result in formation of a propagating crack, but could also undergo ductile failure. For the examination, the full notch creep test (FNCT) was employed with a subsequent advanced fracture surface analysis that was performed using various imaging techniques: light microscopy, laser scanning microscopy, scanning electron microscopy, and X‐ray micro computed tomography scan. FNCT specimens were progressively damaged for increasing durations under standard test conditions applying Arkopal, the standard surfactant solution, and biodiesel as test media were used to analyze the stepwise growth of cracks and crazes. From considerations based on well‐established fracture mechanics approaches, a theoretical correlation between the length of the actual crack and the length of the preceding craze zone was established that could be evidenced and affirmed by FNCT fracture surface analysis. Moreover, the yield strength of a HDPE material exposed to a certain medium as detected by a classic tensile test was found to be the crucial value of true stress to induce the transition from crack propagation due to the craze‐crack mechanism to shear deformation during FNCT measurements.
Highlights
- Progress of crack formation in high‐density polyethylene is analyzed by different imaging techniques
- Determined growth rates depend on distinction between craze zone and crack
- The ratio of the present crack to the anteceding craze zone is validated theoretically
- The transition from crack propagation to ductile shear deformation is identified
- An already formed craze zone may still fail by ductile mechanisms
The present work addresses powder bed binder jetting additive manufacturing by selective magnesium phosphate cement activation. Despite the potential of this technology to aid the digitalization of the construction industry, the effect of processing parameters on the mechanical performance of printed materials has not yet been studied to generate a guideline for the further development of the technology. Statistical methodologies were used to screen the effect of four printing process parameters (printing speed, layer thickness, raster angle, and build direction on flexural and compressive strength). As the exploited technology works with constant fluid pressure, the physical interpretation of the effect of each factor can be considered taking into account the interactions between the binder materials in the powder bed. Analysis of variance (ANOVA) indicated that printing speed and layer thickness significantly affect mechanical performances. Furthermore, the layout of samples for the printing process is preferable to be parallel the printhead movement. An anisotropic behavior was observed, and the samples subjected to compressive forces parallel to the layer plane possessed lower strength values. This effect can be interpreted as a result of a weak area of low density in between layers, leading to a pronounced delamination under compression. Even though the strength of the printed material is not suitable for a structural concrete, it can be marginally improved by design of experiment and optimized for non-structural applications, such as for porous artificial stone. Design of experiment coupled with ANOVA methods can be used in the future to support the development of novel material mixtures, thus expanding the fields of application of this novel additive manufacturing technology.
Several investigation groups have studied the flame-retardancy modes of action and properties of epoxy resins in the past; nevertheless, the selection of suitable flame retardants for epoxy resins remains challenging, and the transfer to fiber composites is difficult. The addition of flame retardants and glass fibers (GFs) to a polymeric system in a fire scenario changes the polymer's pyrolytic path and burning characteristics, reduces the heat released in the combustion, and suppresses the modes of action in the condensed and gas phase. In this study, the thermal analysis, flammability, fire behavior, residue analysis, fire stability, and quantification of modes of action of three different systems with three halogen-free flame retardants (melamine polyphosphate (MPP), ammonium polyphosphate (APP), and silane ammonium polyphosphate (SiAPP)) and three different types of GFs (unidirectional (UD), bidirectional (BD), and woven roving (WR)) will be compared with pure epoxy resin as a reference.
Revolutionizing our polymer industry for adaption to a sustainable carbon circular economy has become one of today’s most demanding challenges. Exploiting renewable resources to replace fossil-fuel—based plastics with biopolymers such as poly(lactic acid) (PLA) is inevitable while using waste streams as a raw material resource at least is promising. When it comes to using PLA as technical polymer, its high flammability must be addressed by flame retardants compatible with the thermoplastic processing of PLA and its compostability. This study proposes microalgae enriched with phosphorus from wastewater (P-Algae) as an elegant way towards a kind of sustainable organophosphorus flame retardant. The concept is demonstrated by investigating the processing, pyrolysis, flammability, and fire behavior of PLA/P-Algae, while varying the P-Algae content and comparing P-Algae with four alternative bio-fillers (phosphorylated lignin, biochar, thermally treated sewage sludge, and metal phytate) with different P-contents as meaningful benchmarks.
This presentation gives an overview of the recent achievements in simulating piping erosion during the installation process of suction bucket foundations for offshore wind turbines. The physical correctness of the code is validated, and the simulation code's performance on the LUMI supercomputer is presented. The simulation results are compared to experimental data.
An Trinkwasserrohren aus ferritischem Stahl (1.4521) sind bei einigen größeren Bauvorhaben massive Korrosionsschäden aufgetreten. Die Leckagen treten ausschließlich durch Spaltkorrosion in Pressverbindungen auf, wo konstruktionsbedingt ein mit Wasser gefüllter Spalt zwischen der Rohr-Außenseite und dem Pressfitting gebildet wird. Im Vortrag werden die gewonnenen Erkenntnisse aus verschiedenen Schadensfällen der jüngeren Vergangenheit vorgestellt.
We introduce a novel adaptive Gaussian Process Regression (GPR) methodology for efficient construction of surrogate models for Bayesian inverse problems with expensive forward model evaluations. An adaptive design strategy focuses on optimizing both the positioning and simulation accuracy of training data in order to reduce the computational cost of simulating training data without compromising the fidelity of the posterior distributions of parameters. The method interleaves a goal-oriented active learning algorithm selecting evaluation points and tolerances based on the expected impact on the Kullback-Leibler divergence of surrogated and true posterior with a Markov Chain Monte Carlo sampling of the posterior. The performance benefit of the adaptive approach is demonstrated for two simple test problems.
Efficient flame retardancy is often achieved only when applying synergistic multicomponent systems. Flame retardants are combined or used together with adjuvants or synergists to enhance their efficiency, reduce the amount required, or reduce the costs; fibers and fillers contribute to fire properties crucially. Although the main flame-retardant modes of action are known, the detailed scientific understanding usually falls short, when it comes to complex synergistic multicomponent systems, the important tiny optimizations, or quantifying in terms of specific fire properties. This paper tries to illuminate the concept of synergistic flame retardants. The need for the multicomponent approach and the main phenomena are described. Thought-provoking impulses are delivered on how the understanding of multicomponent systems promotes the evidence-based development of future flame retardant polymeric materials. Multicomponent systems are discussed in their capacity as general powerful strategy for achieving and optimizing flame retardant polymeric materials.
This paper is based mainly on the overall conclusions and concrete results of several projects performed in the group of the author. Thanks to my (former) students and co-operation partners in these projects. Thanks for financing to DFG (Scha 730/8-1 Scha 730/8-2, Br 3376/1-1, Scha 730/19-1), AiF IGF (438 ZN, 17833N/2, 19078 N/2), and BMBF (03X0111C, 01DN16040).
The development of standards that include simulation models is often based on heuristics that include experimental data that is used to calibrate and validate the simulation models. However, these data and the corresponding calibration procedures are usually not part of the publicly accessible documentation making it very difficult to identify gaps in the current standard or extend it to new innovative solutions. The poster shows an adapted procedure that integrates the complete process into a database and a workflow to be published alongside the standard.
Rotational rheometry test of Portland cement-based materials - A systematic literature review
(2024)
This study systematically reviews 62 papers on the use of rotational rheometry to assess the fresh state behavior of Portland cement-based materials. The research highlights the wide variation in test methods and aims to provide a comprehensive overview. Findings reveal that 50.0% of studies employed vane geometry, despite its limitations in providing transformation equations. Regarding dynamic shearing tests, 67.0% followed a consensus using a pre-shearing step and a step-wise routine with stabilization times ≥ 10 s. While the Bingham model is commonly used, the study emphasizes the importance of considering shear-thinning behavior in cementitious materials. Models like Herschel-Bulkley and modified Bingham may be more appropriate. This review offers insights into testing conditions for rotational rheometry of cementitious materials, serving as a foundation for future research in the field.
Replacing antimony trioxide (ATO) in flame retardant formulations is an urgent task due to its toxicity. There are indications that calcium hypophosphite (CaP) may be a promising replacement. This study investigates the decomposition, fire behavior, and smoke release of brominated flame-retarded acrylonitrile butadiene styrene (ABS) under various fire scenarios like ignition, developing fire and smoldering, while replacing ATO with CaP and CaP/talc. Adding 4 wt.-% of talc to CaP formulations showed beneficial effects on flammability due to changes in the viscosity and barrier properties. Synergism between 8 wt.-% talc and CaP improved the protective layer in the developing fire scenario, resulting in a ∼60 % decrease in the peak of heat release rate and reduction of ∼21 % in total smoke production (ref. ABS+Br+ATO). With a conventional index of toxicity (CIT) of below 0.75, ABS+Br+CaP passes the highest requirements according to EN 45545-2. Overall, the CaP/talc materials improve flame retardancy, show less smoke emission under forced flaming conditions, and prevent chronic intoxication and environmental pollution through smoke particles contaminated with antimony.
Early detection of fatigue cracks and accurate measurements of the crack growth play an important role in the maintenance and repair strategies of steel structures exposed to cyclic loads during their service life. Observation of welded connections is especially of high relevance due to their higher susceptibility to fatigue damage. The aim of this contribution was to monitor fatigue crack growth in thick welded specimens during fatigue tests as holistically as possible, by implementing multiple NDT methods simultaneously in order to record the crack initiation and propagation until the final fracture. In addition to well-known methods such as strain gauges, thermography, and ultrasound, the crack luminescence method developed at the Bundesanstalt für Materialforschung und -prüfung (BAM), which makes cracks on the surface particularly visible, was also used. For data acquisition, a first data fusion concept was developed and applied in order to synchronize the data of the different methods and to evaluate them to a large extent automatically. The resulting database can ultimately also be used to access, view, and analyze the experimental data for various NDT methods. During the conducted fatigue tests, the simultaneous measurements of the same cracking process enabled a comprehensive comparison of the methods, highlighting their individual strengths and limitations. More importantly, they showed how a synergetic combination of different NDT methods can be beneficial for implementation in large-scale fatigue testing but also in monitoring and inspection programs of in-service structures - such as the support structures of offshore wind turbines.
Durch Auslagerungs- und elektrochemische Tests im Labor kann das Korrosionsverhalten verschiedener metallener Werkstoffe beurteilt werden. Aus den Versuchsergebnissen, die in verschiedenen synthetischen Geothermalwässern im Labor erzielt wurden, lassen sich die folgenden Schlussfolgerungen ziehen:
• Die Anfälligkeit für Spaltkorrosion wurde als wichtigster Aspekt für die Werkstoffqualifizierung ermittelt.
• Der niedriglegierte Stahl 25CrMo4 zeigte bei niedrigem Salzgehalt in MB-Geothermalwasser eine gleichmäßige Korrosion unterhalb der akzeptierten Schwelle von 0,3 mm/Jahr. Daher kann er als geeignet für geothermische Bedingungen mit niedrigem Salzgehalt angesehen werden, wie sie für MB getestet wurden. Es besteht keine Notwendigkeit, auf höherlegierte (teurere) Werkstoffe auszuweichen. Ein niedrigerer pH-Wert (wie bei LHD) führt zu Korrosionsraten oberhalb der akzeptablen Grenzwerte, so dass die niedriglegierten Werkstoffe nicht für Flüssigkeiten mit niedrigem pH-Wert geeignet sind.
• Stark salzhaltige Geothermalwässer erfordern höherlegierte Werkstoffe, da die Korrosionsrate von niedriglegiertem Stahl zu hoch ist.
• Der Duplexstahl X2CrNiMo22-5-3 und der Superduplexstahl X2CrNiMoCuWN25-7-4 wurden aufgrund ihrer kritischen Anfälligkeit für örtliche Korrosion in Form von Loch- und Spaltkorrosion unter Betriebsbedingungen nicht als geeignet für geothermische Anwendungen in Geothermalwässern mit einer mit NDB und ORG vergleichbaren Zusammensetzung angesehen.
• Der superaustenitische Stahl X1CrNiMoCu32-28-7 eignet sich für ORG und salzarme Wässer. In NDB-Geothermalwasser wurde er bei 100 °C als geeignet angesehen. Jedoch schränkt seine Anfälligkeit für Spaltkorrosion seine Anwendbarkeit ein. Neben seiner guten Korrosionsbeständigkeit ist sein Repassivierungsverhalten für seine begrenzte Anwendbarkeit in Geothermalwässern mit niedrigem pH-Wert verantwortlich.
• Die Nickelbasislegierung NiCr23Mo16Al wurde als geeignet erachtet und stellt eine sichere Option für den Einsatz in geothermischen Anlagen dar, selbst wenn mit stark salzhaltigem Geothermalwasser gearbeitet wird.
Durch Auslagerungs- und elektrochemische Tests im Labor kann das Korrosionsverhalten verschiedener metallener Werkstoffe beurteilt werden. Aus den Versuchsergebnissen, die in verschiedenen synthetischen Geothermalwässern im Labor erzielt wurden, lassen sich die folgenden Schlussfolgerungen ziehen:
• Die Anfälligkeit für Spaltkorrosion wurde als wichtigster Aspekt für die Werkstoffqualifizierung ermittelt.
• Der niedriglegierte Stahl 25CrMo4 zeigte bei niedrigem Salzgehalt in MB-Geothermalwasser eine gleichmäßige Korrosion unterhalb der akzeptierten Schwelle von 0,3 mm/Jahr. Daher kann er als geeignet für geothermische Bedingungen mit niedrigem Salzgehalt angesehen werden, wie sie für MB getestet wurden. Es besteht keine Notwendigkeit, auf höherlegierte (teurere) Werkstoffe auszuweichen. Ein niedrigerer pH-Wert (wie bei LHD) führt zu Korrosionsraten oberhalb der akzeptablen Grenzwerte, so dass die niedriglegierten Werkstoffe nicht für Flüssigkeiten mit niedrigem pH-Wert geeignet sind.
• Stark salzhaltige Geothermalwässer erfordern höherlegierte Werkstoffe, da die Korrosionsrate von niedriglegiertem Stahl zu hoch ist.
• Der Duplexstahl X2CrNiMo22-5-3 und der Superduplexstahl X2CrNiMoCuWN25-7-4 wurden aufgrund ihrer kritischen Anfälligkeit für örtliche Korrosion in Form von Loch- und Spaltkorrosion unter Betriebsbedingungen nicht als geeignet für geothermische Anwendungen in Geothermalwässern mit einer mit NDB und ORG vergleichbaren Zusammensetzung angesehen.
• Der superaustenitische Stahl X1CrNiMoCu32-28-7 eignet sich für ORG und salzarme Wässer. In NDB-Geothermalwasser wurde er bei 100 °C als geeignet angesehen. Jedoch schränkt seine Anfälligkeit für Spaltkorrosion seine Anwendbarkeit ein. Neben seiner guten Korrosionsbeständigkeit ist sein Repassivierungsverhalten für seine begrenzte Anwendbarkeit in Geothermalwässern mit niedrigem pH-Wert verantwortlich.
• Die Nickelbasislegierung NiCr23Mo16Al wurde als geeignet erachtet und stellt eine sichere Option für den Einsatz in geothermischen Anlagen dar, selbst wenn mit stark salzhaltigem Geothermalwasser gearbeitet wird.
This study explores the acceleration of material design in the concrete industry, focusing on improving carbonation resistance, a key factor in the durability of concrete structures. Traditional tests for carbonation resistance are lengthy, but with the construction industry aiming for sustainable production, finding a balance between carbonation resistance and CO2 footprint is crucial. Our research employs two innovative methods: 1. Applying the Sequential Learning App for Materials Discovery (SLAMD), an AI materials design framework, to an extensive dataset of real-world concrete compositions to selectively test materials that meet market demands: maximum durability, optimal eco-durability, and the best cost-durability trade-off. 2. Investigating 1H Nuclear Magnetic Resonance (NMR) relaxometry as a quick alternative for characterizing carbonation behavior, as it saves time compared to traditional tests and assesses the complete material's pore space. Specific NMR features are then integrated into the material design model, with the model's performance compared against traditional approaches. The results of our study are compelling, demonstrating that materials can be precisely tailored to meet specific requirements with minimal data points. This marks a significant stride in the concrete industry, indicating that NMR-based, low-fidelity surrogate characterizations, combined with a focused, data-driven design approach, can substantially accelerate the development of durable, sustainable concrete mixtures.
The presentations discusses a use case for the optimization of concrete structures where structural and material design are integrated in a computational workflow. The workflow is based on both physics-based and data-based models and experimental data is used to calibrate/train these models with a specific focus on the integration of ucertainties.
Concretes produced from salt aggregate and hybrid alkaline cements, an alkali-activated slag/fly ash blend, or a Portland cement were exposed to a magnesium chloride-rich saline solution ([Mg2+] = 3.6 m, [Cl−] = 8.3 m), representing a solution formed after contact of surface water with evaporite rock (rock salt) in a nuclear waste repository. The hydration and deterioration of the concretes were studied with X-ray diffraction, thermogravimetric analysis, pH mapping and permeability measurements. The results show that calcium silicate hydrate (C-S-H) or sodium-substituted calcium aluminium silicate hydrate (C-N-A-S-H) and Friedel's salt were the major reaction products in the concretes prior to exposure to the saline solution. During exposure to the saline solution, increasing amounts of C-S-H/C-N-A-S-H dissolved, and gypsum and a secondary AFm phase formed. The durability of the concretes improved with increasing amounts of Portland clinker in the cements, due to the associated differences in permeability and chemical resistance. Nevertheless, a massive increase of permeability occurred for all concretes, likely caused by crack formation due to the formation of gypsum from anhydrite in the salt aggregate. Thus, the behavior of the concretes differed from, and was more complex than, the behavior of plain cement pastes.
Oxidative aging induces significant stiffening of asphalt binders that leads to a pronounced reduction in the overall durability of asphalt pavements. The strategic implementation of antioxidant additives provides a potential solution to alleviate this issue. This work presents results from the second phase of the global consortium for antioxidants research aimed at investigating the effectiveness of potential antioxidants in increasing the durability of asphalt binders. Sixteen laboratories around the world participated in this effort and a total of 28 binders from diverse geographical regions were tested. Two promising antioxidants, namely zinc diethyldithiocarbamate (ZDC) and kraft lignin were evaluated in this phase and blended with the binders at specific proportions. Subsequently, a comprehensive investigation was conducted to assess rheological characteristics and chemical properties of the various blends, utilising Dynamic Shear Rheometer (DSR) measurements and Fourier Transform Infrared (FTIR) Spectroscopy. The findings indicate that additives such as ZDC hold considerable promise as an effective antioxidant, particularly when considering a wide diversity of binders. In general, its incorporation does not compromise the rutting performance of the binders and significantly improves fatigue performance. Therefore, research efforts should be focused on exploring additional facets to assess its practical applicability in field.
Chloride binding by the hydrate phases of cementitious materials influences the rate of chloride ingress into these materials and, thus, the time at which chloride reaches the steel reinforcement in concrete structures. Chloride binding isotherms of individual hydrate phases would be required to model chloride ingress but are only scarcely available and partly conflicting. The present study by RILEM TC 283-CAM ‘Chloride transport in alkali-activated materials’ significantly extends the available database and resolves some of the apparent contradictions by determining the chloride binding isotherms of layered double hydroxides (LDH), including AFm phases (monosulfate, strätlingite, hydrotalcite, and meixnerite), and of alkali-activated slags (AAS) produced with four different activators (Na2SiO3, Na2O·1.87SiO2, Na2CO3, and Na2SO4), in NaOH/NaCl solutions at various liquid/solid ratios. Selected solids after chloride binding were analysed by X-ray diffraction, and thermodynamic modelling was applied to simulate the phase changes occurring during chloride binding by the AFm phases. The results of the present study show that the chloride binding isotherms of LDH/AFm phases depend strongly on the liquid/solid ratio during the experiments. This is attributed to kinetic restrictions, which are, however, currently poorly understood. Chloride binding by AAS pastes is only moderately influenced by the employed activator. A steep increase of the chloride binding by AAS occurs at free chloride concentrations above approx. 1.0 M, which is possibly related to chloride binding by the C–(N–)A–S–H gel in the AAS.
Ground Granulated Blast-Furnace Slag (GGBFS), a by-product of the iron-making process, has gained significant attention as a supplementary cementitious material and has become increasingly popular in recent years due to its remarkable properties. GGBFS can significantly reduce the environmental impact of cement production when it comes to building concrete structures. GGBFS can either be blended with ordinary Portland cement (OPC) (up to a 90% replacement), or it can be used in the production of alkali-activated materials (AAMs). However, a comprehensive understanding of the pore solution composition is necessary for understanding various aspects of cementitious materials and their durability, including corrosion behavior, passivation of steel, and resistance to deteriorative processes. In the present work, the pore solutions of seven different GGBFS-containing cements (alkali-activated slag, alkali-activated slag/fly ash blends, a hybrid alkaline cement, CEM III/C, and CEM III/B) were extracted and analysed by inductively coupled plasma-optical emission spectroscopy, ion chromatography, pH, redox potential, and conductivity measurements. For comparison, a Portland cement pore solution was analysed similarly. The Concentrations of reduced sulfur were noteworthy in all GGBFS-containing cements, particularly in alkali-activated cements, where concentrations were notably higher compared to standard cements. The redox potentials of the pore solutions were primarily dictated by the concentrations of reduced sulfur, although other factors may contribute. Additionally, sulfur species in the pore solutions had an impact on pH, electrical conductivity, and other properties pertinent to the corrosion of reinforcements.
Es werden die Ergebnisse eines mehrjährigen Forschungsvorhabens der BAM in Zusammenarbeit mit Straßenbauverwaltungen der Länder und Industriebeteiligten zur betriebstechnischen Ausrüstung von Straßentunneln präsentiert. Schwerpunkte waren die Bestimmung der Korrosivität der Atmosphäre von 3 ausgewählten Straßentunneln, die Analyse korrosionsrelevanter Ablagerungen und von Klimadaten. Die Auswirkungen dieser Einflussgrößen auf die Dauerhaftigkeit von Konstruktionen aus nichtrostenden Stählen wurde ermittelt und in Abhängigkeit verschiedener Einflussparameter dargestellt. Die Ergebnisse der systematischen Untersuchungen an Prüfköpern decken sich mit Beobachtungen an realen Bauteilen. Spaltbehaftete Konstruktionen aus Werkstoffen der CRC III führen demnach in Zeiträumen zwischen 10 und 15 Jahren zu Korrosionserscheinungen, welche die technische Sicherheit beeinträchtigen können und die erwartete Dauerhaftigkeit nicht erfüllen. Die Folge sind zusätzliche Sperrungen und ein vorzeitig notwendiger Unterhaltsaufwand, die erhebliche Kosten verursachen. Im Ergebnis ist eine Überarbeitung des aktuellen Regelwerkes erforderlich, um die angestrebte Dauerhaftigkeit von 30 Jahren zu gewährleisten.
The corrosion behavior of galvanized steels and zinc components under atmospheric exposure depends mostly on the corrosion product‐based cover layer formation under the prevailing conditions. The use of agar‐based gel electrolytes makes it possible to use electrochemical methods to obtain a characteristic value from these cover layers that describe their current and future protective capacity. It is shown here that different states of galvanized steel can be distinguished very well under laboratory conditions and that this method is also suitable for use under practical conditions. Based on the characteristic values and assuming future time of wetness, it is very easy to draw up a forecast for the future corrosion rate, which provides plausible values.
To combat climate change the share of renewable energy production must increase drastically. Offshore energy production – offshore wind and power-to-X – are crucial to achieving climate targets. However, the impact of these offshore constructions – wind turbines and production platforms – on the marine environment remains unclear in many aspects. Potential sources of chemical emissions are corrosion protection systems, remobilization of contaminants from old sediments during construction, the brine of desalination plants and increased shipping for maintenance and transportation. In order to minimize the environmental impact of renewable energies, close monitoring is essential. The goal of this project is the development of a monitoring concept for an offshore power-to-X production platform.
Maritime exposure poses particular challenges for corrosion
protection in plant construction. In addition to the right choice
of materials, special design features that can have an impact
on corrosion resistance must also be taken into account to
ensure long-lasting corrosion protection. In practice, structural
crevice arrangements are unavoidable, and therefore the
crevice corrosion resistances of stainless steels are of
particular importance. These and other influences are being
investigated in this joint project.
While alkali-activated binders offer certain advantages over traditional Portland cement binders, particu¬larly in terms of resistance against chemical attacks and potentially environmental footprint, their degra¬dation mechanisms remain incompletely understood at present, specifically carbonation. Thus, this study investigates the impact of natural and accelerated carbonation (1% and 4% CO2) on three different compositions of alkali-activated concretes: 100% calcined clay (C100) binder, 100% ground blast furnace slag (S100) binder, and a 40% calcined clay and 60% blast furnace slag blend (C40S60). C100 concretes exhibit faster carbonation kinetics, with five times greater natural carbonation depths than S100. This difference diminishes under accelerated carbonation, showing a 1.5 times difference for 1% CO2 and complete carbonation for 4% CO2 at 90 days. The results thus confirm that accelerated carbonation testing of low-Ca alkali-activated concretes yields results that are not representative of natural carbonation. The C40S60 sample demonstrates a carbonation profile similar to a CEM I concrete, i.e., a high carbonation resistance. Microstructure analysis indicates the formation of three polymorphs of calcium carbonate for S100 (calcite, vaterite, and aragonite), with a higher CO2 concentration favouring aragonite over vaterite. C100 exhibits no calcium carbonates; instead, sodium carbonates form, including trona for 4% CO2 and natrite for both accelerated tests. C40S60 shows calcium and sodium carbonates, although to a lesser extent, containing predominantly calcite and minor signals of natrite. Suitable compositions, like C40S60, prove as effective during natural or accelerated carbonation tests as conventional Portland cement concrete.
3D concrete printing is an innovative new construction technology offering the potential to enable an efficient production of individual structures with less consumption of resources. The technology will mainly shape the future construction philosophy, automate the build process and help reaching the climate goals in civil engineering. From the design of a structure to the printed component, many individual steps based on different software are required which must be repeated for each new or changed structure. First, the geometry of the structure is created in a CAD program. Second, the print path is defined in a slicer software creating the machine code for the printer (G-Code). Finally, the structure can be printed. Furthermore, a numerical model of the printed structure is necessary for process optimization and control. In that way the number of test prints can be reduced, costs can be saved, and the component behavior can be predicted. For those purposes, an automated workflow allowing to run all steps or individual steps without interacting with each individual software program is required. Furthermore, changes in parameters or the exchange of parts (using a different design or different printer) must be possible in a simple manner. In the presented work, such an automated workflow based on the example of a parametrized wall element for extrusion-based concrete printing is developed. The investigated wall structure is parametrized using the global geometry parameters: height, width, thickness, radius, kind of infill structure (honey-comb, zig-zag) and number of repeated infills. All above mentioned steps are implemented via python interfaces using pydoit as workflow tool. General interfaces with prescribed input and output files are defined allowing adaptations for different software and tools. The described workflow is tested by performing a test series investigating the influence of the in-fill structure on the mechanical properties of the test walls.
Interlaboratory studies are common tools for collecting comparable data to implement standards for new materials or testing technologies. In the case of construction materials, these studies form the basis for recommendations and design codes. Depending on the study, the amount of data collected can be enormous, making manual handling and evaluation difficult. On the other hand, the importance of the FAIR (findable, accessible, interoperable, and reusable) principles for scientific data management, published by Wilkinson et al. in 2016, is constantly growing and changing the view on data usage.
The benefits of using data management tools such as data stores/repositories or electronic laboratory notebooks are many. Data is stored in a structured and accessible way (at least within a group) and data loss due to staff turnover is reduced. Tools usually support data publishing and analysis interfaces. In this way, data can be reused years later to generate new knowledge with future insights. On the other hand, there are many challenges in setting up a data repository, such as selecting suitable software tools, defining the data structure, enabling data access, and understanding by others and
ensuring maintenance, among others.
This talk discusses the advantages and challenges of setting up and applying a data repository using the interlaboratory study on the mechanical properties of printed concrete structures carried out in RILEM TC 304-ADC as example. First, the definition of a suitable data structure including all information is discussed. The tool-dependent upload process is then described. Here, the data
management system openBIS (open source software developed by ETH Zurich) is used. Since in most cases an open compute platform allowing access from different organisations is not possible or available due to data protection and maintenance issues, tool-independent export options are discussed and compared. Finally, the different query and analysis possibilities are demonstrated.