Table 3 - uploaded by Michael de Bouw
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During the 19th century various new construction materials became available in a short time. This paper deals with the quest for a methodology to differentiate wrought iron from mild steel by using a combination of several onsite non- destructive testing instruments. A mobile Vickers hardness tester and an optical microscope were used to determine...
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Context 1
... convert the hardness values into ultimate tensile strength, we used Uconeer [7], which is a program based on an extensive set of experiments on modern carbon steel and steel alloys, as conversion tables for historic steel do not exist (yet). Table 3 indicates that the ultimate tensile strength could be predicted from the hardness values within a margin of 11% for ingot samples. This might not be accurate enough for a structural calculation, but will enable engineers to determine whether the steel qualities of two structural elements are comparable. ...
Citations
... In addition, a layered structure with micro-cracks and a form of graphite (if any) can be detected by a scanning electron microscope [7,17]. To study the microstructure, grain size, and inclusions of the material, the specimens were mechanically prepared and investigated by optical microscopy analysis. ...
Focusing on heritage structures, various non-destructive tests (NDT) or minor-destructive techniques (MDT) can be applied while the application of destructive testing is limited. The probabilistic models for tensile and compressive strengths of historic cast iron are developed on the basis of destructive tests (DTs) and MDTs, respectively. NDT results are critically compared with DTs. It appears that numerous uncertainties affecting estimated resistance can be treated by statistical approaches along with the semi-probabilistic verification method. Non-destructive hardness tests can hardly be used to estimate strength of cast iron and must be supplemented by destructive tests.
p>The mechanical properties of historic metal materials exhibit a considerable scatter dependent on periods of construction and the region of a producer. Assessments of historic metal bridges then need to be based on measurements and tests. The use of non- or minor-destructive tests (NDTs) is often preferred over to destructive tests (DTs) to reduce the cost of structural survey. This contribution explores the measurement errors associated with common NDT hardness techniques and quantifies uncertainties in design (assessment) values of resistance. When deriving the partial factor, the uncertainty in geometry and model uncertainty is considered along with the variability of a material property and measurement error. Numerical studies reveal the effects of measurement error and model uncertainty (bending, buckling) on assessment values of resistance. A unity mean and coefficient of variation of 12% might be adopted for the measurement uncertainty of the hardness methods under study as a first approximation. On average, the true assessment resistance is by ~15% larger than that based on a NDT survey. Model uncertainty affects the partial factor for resistance of historic metal bridges.</p
Waiting for a train at London St Pancras railway station or reading a book on the Berlin underground are simple everyday actions. Conversely, preserving the service life of such historical metal structures enabling those routine actions is a challenge. The overall safety and stability of historical iron and steel structures and, more in particular, the state of their connections, are of concern to engineers, architects and heritage care specialists. Rivets were the primary fastener used to fabricate these connections through a technique called hot riveting. Although well developed in the nineteenth century, hot riveting fell into disuse when the welding technique was invented. Nowadays, the appraisal of riveted connections raises numerous theoretical and practical issues that remain to be solved. Therefore, we reviewed international historical literature and carried out experiments. This study unravels the technology and design of historical riveted connections built in France and Belgium (1840s-1940s).
Major evolutions occurred at the turn of the 20th century. The material iron was replaced by steel, rivets were not installed by hand anymore but with machines, and the design of riveted connections relied on a scientific approach. The appraisal of riveted structures of that period thus calls for additional care. The knowledge of past techniques and design methods can help engineers apprehend the assessment of riveted connections with more confidence. The study supports decisions-makers and workmen for inspection, structural assessment and intervention purposes. We should strive to preserve both the service life and the heritage value of historical metal structures belonging to the city's landscape for the decades and hopefully centuries to come.
