620 Ingenieurwissenschaften
Filtern
Dokumenttyp
Volltext vorhanden
- nein (3)
Gehört zur Bibliographie
- ja (3) (entfernen)
Schlagworte
- Deutschland (3) (entfernen)
Institut
In vielen Ländern mit hochbelasteten Verkehrsinfrastrukturen ist Bauen mit vorgefertigten Modulen anerkannter Stand der Technik und wird stetig eingesetzt. In der Regel sind es Überbauten mit einem einzelligen Stahlbetonhohlkasten, die, in Segmente aufgeteiltm vor Ort meist im Freivorbau zusammengefügt und mit externen Spanngliedern zusammengespannt werden. Modulbauweisen im Verbundbau sind die Ausnahme, bieten aber gegenüber dem Spannbeton in der Herstellung, beim Transport und der Montage erhebliche Vorteile, da die Fahrbahnsegmente auf die Längsträger einfach aufgelegt werden können. Mit der vorstellten VSM-Bauweise können robuste Überbauten vin Ein- und Mehrfeldbauwerken in kürzester Bauzeit mit geringster Verkehrbehinderung wirtschaftlich realisiert werden.
Roebling became acquainted with Navier's theory at the Berlin Bauakademie in 1824/25. During his road planning work in Westphalia, he developed several suspension bridge projects in 1828. Roebling's travels along the Rhein and Ruhr in the winter of 1828 were connected with these projects. Roebling supplemented his notes on Dietlein's bridge-building lectures at the Berlin Bauakademie with excerpts from newer literature on suspension bridges. Under the title "Remarks on Bridge Construction" he discussed the results of his studies. Four known bridge projects can be distinguished. Two are only elaborated as an idea, in one case the project is only known by official letters. Only in the case of the Freienohl Bridge is there an exact description of the project. None of them have been brought to realization. Security considerations of the Berlin Oberbaudeputation probably led to the decision not to execute Roebling's Finnentrop project. This decision ought to be understood within the context of a bridge collapse in Nienburg /Saale in December 1825. When Roebling immigrated to the United States, he used his knowledge in construction methods and experiences with an experimental approach. For this reason, it is interesting to compare the early German projects with his first American bridges. While Roebling's first canal aqueducts combined suspension bridges with trusses, the Niagara Bridge marks a radical step forward to another dimension and to a new approach that emphasized thinking in terms of "systems". Interestingly, he also consistently maintained his construction principle for attaining stability by using rigid, wrapped main cables, inclined stays and wooden trusswork. Although he later used wrought iron profiles, he continued to use wooden constructions in his basic plans for a long time. There is no evidence that he made any contribution to the theories of trusses in a manner comparable with Whipple, Culmann, Gerber or others. Roebling's special talent lay in his constructive gifts.
The German Association for Water, Wastewater and Waste e.V. (DWA) has published a new standard for the dimensioning, construction, and operation of constructed wetlands for treatment of domestic and municipal wastewater. The changes to the standard are based on a wide range of experience gained in recent years in Germany and Europe. For the first time ever, the standard has been officially translated and published in English. This paper summarizes the new standard for secondary treatment of domestic wastewater with classical one-stage unsaturated vertical flow (VF) wetlands, VF wetlands with lava sand for treatment of wastewater from combined sewer systems, and actively aerated VF and horizontal flow (HF) flow wetlands. Two-stage unsaturated VF wetlands treating raw wastewater (French VF wetlands), are also included in the new standard. HF wetlands are no longer described in the standard for secondary treatment of domestic wastewater. This does not exclude their application. Existing HF wetland systems in Germany may continue to be operated so long as effluent parameters are met and proper operations and maintenance is ensured. This paper gives an overview of the new design standard, including key information on wastewater type and loading, as well as primary attributes of each wetland design.