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Cast iron arch bridges were built in the late 18th and early 19th century across Europe. After the famous Iron Bridge in the Ironbridge Gorge in Coalbrookdale in England, being now part of the UNESCO world heritage, many cast iron bridges followed and substituted timber bridges. A series of cast iron bridges has been built in central Europe, in Laasan, Breslau, (now Wrocław), in Berlin, Potsdam, Bad Muskau and Schwerin. The paper gives an overview about the current state of some remaining cast iron arch bridges, typical damage cases, material properties and rehabilitation. Most of the old cast iron arch bridges serve as pedestrian bridges. Some of these bridges have been strengthened to increase the traffic load. Different rehabilitation measures as substitution of parts of the bridges and strengthening using Carbon Reinforced Polymers (CFRP) are discussed.
Experimental and analytical investigation of the TMF-HCF lifetime behavior of two cast iron alloys
(2016)
The superposition of small amplitude, high frequent loading cycles (HCF) to the slow, large amplitude, TMF loading cycles can significantly reduce the TMF life, i.e. the number of TMF blocks until failure. In this work, the combined TMF-HCF loading has been experimentally investigated for two cast iron alloys. Both alloys contain globular graphite nodules but the first one has a ferritic while the second one has an austenitic crystal structure. In particular, the influence of the HCF frequency, of the HCF loading amplitude and of the location of the superposed HCF cycles has been investigated. It was observed that the HCF frequency has a limited impact on the TMF fatigue life. In other words, the number of superposed HCF-cycles has only a slight influence on the TMF fatigue life, which contradicts the linear damage accumulation rule concept. On the other side, the HCF-strain amplitude has a highly non-linear influence on the TMF fatigue life.
The experimental results can be understood in terms of a fracture mechanics based damage mechanism [1]: Cracks readily initiate due to the TMF loading and the duration of the growth of the cracks up to a few mm controls the fatigue life. If HCF-loading cycles are superposed, cyclic crack propagation dramatically accelerates at some stage. This stage is related to the existence of a threshold for crack growth under pure HCF-conditions and largely controls the fatigue life of the combined loading.
The previous ideas have been expressed in a model that can be very simply applied to provide the fatigue life reduction factor due to the superposed HCF cycles. It only contains two additional adjustable parameters and can be combined with any TMF model.
Microbiologically Influenced Corrosion of Cast Iron Containers for High-Level Nuclear Waste Disposal
(2022)
Ductile and corrosion resistant cast iron is investigated as a potential container material to store high-level nuclear waste (HLW) in deep geological repositories (DGR) in claystone bedrock. The dynamic corrosion process is dependent on the conditions present in the DGR which are influenced and/or controlled by geochemical parameters (e.g., redox potential, pH, presence of and ionic concentration in (pore-)water), physical parameters (e.g., pressure), and the influence of metabolically active microorganisms. Cast iron corrosion will occur at the intersection of container and its decontaminable coating with the bentonite backfill material which contains natural microbial populations.
The conditions in a DGR are simulated in microcosm experiments to investigate the impact of microbiologically influenced corrosion (MIC); the microcosms contain: B27 bentonite, synthetic pore water, N2 or N2-CO2 atmosphere, cast iron coupons, as well as the bacterium Desulfosporosinus burensis (isolated from repository depth in Buré, France). Three coupon configurations will be used: untreated, coated with decontaminable coating, and coated with decontaminable coating which has been damaged to simulate possible damages. The microcosms will be examined for bio- and geochemical parameters, such as pH, redox potential, mineral phases, sulphate concentration, Fe(II):Fe(III), changes in microbial populations, and the corrosion process for formation of corrosion products, and potential microbial influence, after a 270-day incubation period at 25°C under anaerobic conditions. In subsequent experiments, the sorption behavior of lanthanides and actinides onto the membranes of viable cells and spores of D. burensis, as well as the surface of corroded cast iron coupons will be investigated.