Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Dokumenttyp
Referierte Publikation
- nein (112) (entfernen)
Schlagworte
- UHPC (12)
- Alkali-Kieselsäure-Reaktion (9)
- Betonfahrbahndecke (9)
- Concrete (8)
- Durability (7)
- Beton (6)
- Fatigue (6)
- Hydrothermal treatment (6)
- Innenhydrophobierung (6)
- Zonation (6)
Organisationseinheit der BAM
- 7.1 Baustoffe (112) (entfernen)
Eingeladener Vortrag
- nein (43)
Die Ausführung von Abdichtungssystemen insbesondere an Ingenieurbauwerken der Verkehrsinfrastruktur greift in die unmittelbare Verfügbarkeit/Nutzbarkeit des Bauwerks ein und erfolgt deshalb i.a.R. unter höchstem Zeitdruck. Neuere materialtechnische Entwicklungen im Bereich der Flüssigkunststoff-Systeme erlauben kürzere Ausführungszeiten in einem erweiterten Einsatzspektrum. Zur Sicherstellung anforderungsgerechter Gebrauchseigenschaften des gesamten Brückenabdichtungssystems gibt die vorliegende Veröffentlichung Hinweise für die einzuhaltenden Baugrundsätze, bautechnologische Besonderheiten und Erfordernisse im Umgang mit Polymethylmethacrylat (PMMA) sowie qualitätssichernde Maßnahmen.
Acoustic emission testing
(2018)
Derzeit ist die Instandhaltung von großen Betontragwerken wie Brücken oder Windenergieanlagen problemorientiert und von einem reaktiven Vorgehen geprägt. Das bedeutet, erst wenn sichtbare Schäden vorliegen, werden diese meist unter Beeinträchtigung des Betriebs instand gesetzt. Im Hinblick auf die Entwicklung von prädiktiven Instandhaltungsstrategien, deren Fokus in der langfristigen Bauwerksüberwachung und der Vorhersage von Schädigungsentwicklungen liegt, wurde die Anwendung von Ultraschallverfahren für die Identifizierung der Degradationsprozesse von Betontragwerken unter Ermüdungsbeanspruchung untersucht. Hierzu fanden Arbeiten im vom Bundesministerium für Wirtschaft und Klimaschutz (BMWK) geförderten Verbundprojekt WinConFat zum "Einfluss der Probengeometrie und -größe auf die Ermüdung von Beton" an der Bundesanstalt für Materialforschung und -prüfung (BAM) und zu den "Methoden zur Zustandsanalyse von Windenergieanlagen" am Institut für Massivbau (IfMa) der Leibniz Universität Hannover (LUH) statt, welches zudem vom Deutschen Beton- und Bautechnik Verein e.V. (Forschungsvorhaben DBV-311) gefördert wurde. Dabei wurden verschiedene Einflussfaktoren auf die Schädigungsentwicklung unter Ermüdungsbeanspruchung wie die Probekörpergröße, das Belastungsniveau und die Betonfestigkeit untersucht. Als Schädigungsindikator und Vergleichsparameter wurden die Ultraschallgeschwindigkeit und der dynamische E-Modul des Betons verwendet. Um das Potential der Schädigungserfassung im Beton mittels Ultraschallprüfung umfassender zu bewerten, wurden zusätzlich Versuche an Betonproben unter monoton steigender Belastung, Kriechversuche, Temperaturversuche und Untersuchungen an großformatigen Balken durchgeführt.
In concrete pavements, damages occurred which are related to an Alkali-Silica-Reaction (ASR). Although the background for such an ASR has been studied extensively, special conditions in pavements increase this reaction significantly. These are especially the superposition of microstructural degradation caused by cyclic loading with an external alkali supply. Previous investigations of ASR focused mainly on the material itself (aggregates, cements, assessment of the concrete) while these special circumstances have not been considered. Concrete pavements are subjected to cyclic loadings by traffic and climate changes.
Within cooperative research projects the different interdependent influencing factors for a damaging ASR in concrete pavements are studied by experiments as well as by numeric modelling. On the micro-level the ASR-related processes within the aggregate, such as gel-formation or ion-transport, are investigated. On the meso-level, the project focuses on the characterization of degradation effects in the concrete microstructure due to cyclic loading. Further, special attention is paid to the transport behavior of fluids in such pre-damaged concrete structures with and without the effect of overrunning tires as well as the impact on the ASR itself. Finally, on the macro-level the risk of an ASR-damage is assessed.
A new approach towards performance-related design and scientific evaluation of joint sealing systems
(2020)
While there is a permanent improvement of concrete pavement mixtures and pavement construction types over the last decades, the state-of-the-art joint sealing materials and joint constructions seem to stagnate on an antiquated empirical level. This status has been reaffirmed in the latest European standard.
The consequences in the motorway network due to unsatisfying capability and durability of joint sealing systems are unacceptable. In addition, inadequate traffic performance (noise emissions, roll-over comfort) and traffic safety losses in the joint area of concrete pavements are existing challenges. These deficits and weaknesses reflect a demand for joint sealing materials and constructions whose approval requirements take functional aspects into account. Furthermore a sufficient analysis of decisive loads and a practice-oriented method to evaluate the requirements towards performance and durability is still missed.
In this contribution decisive loads to German highways are analyzed. The design of test specimen for representative functional testing of joint sealing systems is discussed. The focus is on the geometry of the test specimens and the used concrete mixture. Finally, a new approach for a function-orientated test concept that considers representative load functions is presented. The potential of this approach to validate the durability and capability of various joint sealing systems is also presented using an example.
While there is a permanent improvement of concrete pavement mixtures and pavement construction types over the last decades, the state-of-the-art joint sealing materials and joint constructions seem to stagnate on an antiquated empirical level. This status has been reaffirmed in the latest European standard. The consequences in the motorway network due to unsatisfying capability and durabilty of joint sealing systems are unacceptable. In addition, inadequate traffic performance (noise emissions, roll-over comfort) and traffic safety losses in the joint area of concrete pavements are existing challenges. These deficits and weaknesses reflect a demand for joint sealing materials and constructions whose approval requirements take functional aspects into account. Furthermore a sufficient analysis of decisive loads and a practice-oriented method to evaluate the requirements towards performance and durability is still missed. In this contribution decisive loads to German highways are analyzed. The design of test specimen for representative functional testing of joint sealing systems is discussed. The focus is on the geometry of the test specimens and the used concrete mixture. Finally, a new approach for a function-orientated test concept that considers representative load functions is presented. The potential of this approach to validate the durability and capability of various joint sealing systems is also presented using an example.
Algal biofilm façades are an alternative to traditional green façades which can help to improve biodiversity and air quality within cities. They present a low maintenance approach in which subaerial algae are grown directly on concrete substrates. The intrinsic bioreceptivity of the substrate is a critical factor in successful facade colonisation. Existing research has identified several environmental and material properties which influence concrete bioreceptivity, however a consensus has yet to be made on which properties are most influential and how the interaction between properties may promote algal biofilm growth under specific conditions.
Dynamic characterisation of historic bell-tower using a sensitivity-based technique for model tuning
(2018)
The most relevant results of the vibration-based investigations performed on a historic masonry tower in Italy namely the Santa Maria a Vico bell-tower is here presented. The first part of the study involves preliminary full-scale ambient vibration measurements in operational conditions and dynamics-based finite element (FE) modelling. At first, a manual tuning of the uncertain parameters of the model was carried out to adjust material properties, soil-structure interaction and constraining effect of the neighbouring structures. Then, based on the sensitivity analysis, only the most sensitive parameters were chosen as updating parameters. Finally, a model updating technique based on a sensitivity-based method was used to minimise the error between experimental vibration data and numerical response values. To this aim, a residual vector defined as the weighted difference between the measured quantities and calculated quantities was used. The uncertain structural parameters of the FE model were identified by minimising a robust penalty function. The calibrated model was used as an important tool for the seismic assessment of the structure using pushover analysis. Since the assumed value of the masonry compressive strength is the most sensitive parameter of non-linear behaviour, a sensitivity analysis was performed considering reference values in the range of interest. The seismic safety corresponding to increasing levels of the seismic hazard was finally investigated.
Utilisation of alkali-sensitive aggregates for concrete pavements by internal hydrophobisation
(2021)
In order to avoid the increased ASR damage to concrete pavements in the German motorway network in the future, the ARS 04/2013 introduced mandatory suitability tests to exclude alkali-sensitive aggregates in new construction measures. This resulted in a significant reduction of suitable aggregates. Against this background, borderline alkali-sensitive aggregates are to be made usable by adding an internal water repellent agent during concrete casting. The ASR avoidance strategy is based on the significant reduction of the penetration of water and de-icing salt solution into the concrete pavement. Laboratory tests show that, with a suitable active ingredient, the ASR damage process can be significantly reduced with internal hydrophobisation. The disadvantage is that this is associated with a deterioration of the mechanical properties and the resistance to freeze-thaw with de-icing salt. The aim of the ongoing research is to reduce these disadvantages through targeted modification of the hydrophobising agent and air-entraining agent.