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- 2021 (5) (entfernen)
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Schlagworte
- Acoustic emission analysis (1)
- Bending (1)
- Betondickglasfenster (1)
- Carbonation (1)
- Concrete beam (1)
- Concrete-glass windows (1)
- Cracks (1)
- Dalle-de-verre (1)
- Digital image correlation (1)
- Distributed fibre optic sensor (1)
Organisationseinheit der BAM
Am Ende des 19. und zu Beginn des 20. Jahrhunderts wurden auch in Berlin vermehrt Bauwerke mit einer Fassadenverblendung aus Eifeler Tuffsteinen errichtet. Die Eifeler Tuffsteine zeichnen sich aufgrund ihrer hohen Porosität einerseits durch eine gute Verarbeitbarkeit aus. Andererseits sind sie nur schwach gebunden und besitzen deshalb eine geringe Verwitterungsbeständigkeit.
Concrete-glass windows or commonly referred to as “Dalle de Verre” windows are prevalent in historical monuments across Europe. “Dalle de Verre” windows were made by placing cut stained glasses, of various shapes and sizes, into a steel reinforced concrete frame. In addition to the steel reinforcement, a few steel wires run across the concrete elements to hold the glass windows into place. Much of these structures have been damaged due to carbonation of the thin concrete covers and consequent corrosion of the steel reinforcement; and exhibit several cracks due to the expansive nature of corrosion products formed at the steel–concrete interface. This study focussed on understanding the efficacy of electrochemical realkalisation in reinstating the passive state of the steel reinforcement embedded in such concrete glass windows. Simulant “Dalle de Verre” windows (representative of windows at Kaiser-Wilhelm Gedächtniskirche) were produced using different cements with a water/cement ratio of 0.6 and carbonated under accelerated conditions. Post carbonation, the concrete glass windows were electrochemically realkalised using a sacrificial anode. The influence of highly alkaline conditions due to electrochemical realkalisation on the glass-concrete interface has also been investigated. This study shows that the passive state of the steel reinforcement in “Dalle de Verre” windows, particularly at the Kaiser-Wilhelm Gedächtniskirche (memorial church) in Berlin, can be reinstated using the electrochemical realkalisation method.
Die Kaiser-Wilhelm-Gedächtniskirche (KWG) gilt als eine der wichtigsten Sehenswürdigkeiten Berlins in der City West und als ein herausragendes Beispiel für die „Dalle de Verre“ Verglasungen in sakralen Gebäuden. Der vorliegende Beitrag widmet sich der Fassade und den Glasfenstern des neuen Glockenturms, wobei die beschriebenen Szenarien aufgrund der annähernd gleichen Bauweise der restlichen neuen Baukörper in weiten Teilen starke Analogien aufweisen und insofern übertragbar sind.
Grouted connections are intensively used in offshore rigs, platforms as well as jacket and monopile offshore wind turbine structures. Being located in remote offshore conditions, these connections can experience considerable adverse loading during their lifetimes. Degradation was reported inside similar connections, which were installed in the last three decades. Grouting in the offshore sites may often be proven difficult, which eventually leads to reduced load-bearing capacity of connections in the long run. Thus, repair and rehabilitation of such connections should be planned ahead to minimize operational delays and costs. In this study, scaled grouted connections were manufactured using a novel mould, whose integrity were monitored using digital image correlation (DIC). The connections were loaded under static load to visualize the main failure pattern using distributed fibre optic sensors and acoustic emission (AE) analysis. Grouted connections were then repaired using a cementitious injectable grout. The effectiveness of the grout injection was monitored using dye penetration technique. Finally, specimens are reloaded to identify the potential of such repair for grouted connections.
Bending beams and slabs are typical examples for structural elements used for reinforced concrete structures such as bridge girders, T-beams and bridge decks. Their strength related failure modes at maximum loading can be divided into bending and shear failure. The failure of beams loaded in bending can occur with or without indication. Therefore, conventional design concepts aim on failure modes with sufficient indication (e.g. large deflections or cracks), as it occurs in the case of secondary flexural compression failure. These indicating factors can also be used for Structural Health Monitoring (SHM) of civil infrastructure systems (e.g. bridges) to identify structural changes. In this context, non-destructive testing (NDT) methods offer different techniques for measuring deflections or crack formation and opening. However, profound knowledge on the determining failure modes of bending beams and their detection by NDT methods is required for the reliable application of SHM. Different NDT methods have been used in this study for analysing the load-bearing behaviour of a reinforced concrete beam in bending. The different measuring techniques are briefly described and their applicability is discussed by means of experimental results. For this purpose, the load-bearing behaviour of a reinforced concrete beam having a span of 2.75 m was investigated in a four-point bending flexural test at laboratory scale. The focus is on the characterization of determining failure modes by optical NDT and the comparison with classical measuring techniques (e.g. deformation measurements by displacement transducers). The bending beam was equipped with two single-mode (SM) sensor fibres. One fibre served as Distributed Optical Fibre Sensor (DOFS), whereas the other fibre contained Fibre Bragg Grating (FBG) sensors. In addition, optical deformation measurements using Digital Image Correlation (DIC) and Stereophotogrammetry (SP) were conducted.