1,809 research outputs found
The strength of concrete in historical bridges
No full textTo assess the performances of existing Reinforced Concrete (RC) bridges, the current structural analyses need the definition of material properties, and in particular of concrete strength. Such parameter is usually measured by means of destructive tests on concrete cores drilled form a bridge, or by means of indirect non-destructive analyses, such as the acoustic techniques or the rebound hammer test. Nevertheless, in several cases, a rough estimation of the compressive strength of concrete is sufficient, without performing any test on the structures. This is the case of some historical RC bridges, which date back to the early ages of last Century and are cur-rently in service in Italy. Accordingly, the strength-for-year curves have been introduced to calculate the aver-age strength (and the percentiles) of a concrete cast in a specific year. They are based on the results of tests performed on concrete cubes, and stored in a database available at the Politecnico di Torino (Italy). The use of the strength-for-year curves improves the effectiveness of the rapid assessment procedures. As a result, the priorities of retrofitting, necessary to mitigate the risks associated with the prolonged service of RC bridges, can be better identified
Analogies in fracture mechanics of concrete, rock and ice
No full textBoth in architecture and arts, the golden ratio has been taken into consideration most exclusively for its geometrical properties. Specifically, among all the proportions, the golden ratio can inspire beauty and aesthetic pleasure. Indeed, it has driven, in an implicit or explicit manner, the construction of buildings for centuries. Nevertheless, as discussed in the present paper, also fracture mechanisms in brittle and quasi-brittle materials call the golden ratio into play. This is the case of fracture energy and fracture toughness, in which the irrational number 1.61803 recurs when the geometrical dimensions vary. This aspect is confirmed by the results of different experimental campaigns performed on concrete and rock beams and ice sheets. In other words, it can be argued that the centrality of the golden ratio for quasi-brittle structures has profound physical meanings, as it can bring together the aesthetic of nature and architecture, and the equilibrium of stress flow in solid bodie
STRUCTURE OF THE ART-SPACE IN THE STORY "I" BY A.P. POTEMKIN
No full textThe author performs the analysis of the art space structure in A.P. Potemkin's story "I". Several interrelated spatial models are allocated and described: household space, natural space, social space, psychological space, transpersonal space
Pressure drop and turbulence statistics in transpired pipe flow
No full textMeasurements of turbulent flow in a horizontal pipe subjected to wall transpiration are presented. Results include data on global flow rates and pressure drop, and local mean and fluctuating velocity profiles. Two distinct flow transpiration rates are studied, = / = 0.0005 and 0.001. The effects of flow transpiration on the friction-coefficient are compared with theoretical predictions. The theory furnishes predictions accurate to 3\%
Fully Turbulent Mean Velocity Profile for Purely Viscous non-Newtonian Fluids
No full textThe characteristic near wall behavior of turbulent flow of purely-viscous non-Newtonian fluids is discussed for both power-law (P.-L.) and Herschel-Bulkley (H.-B.) rheological models. A proper scaling is presented for H.-B. fluids to establish an analogy with power-law fluids with same flow index. To provide reference data for turbulent flow of non-Newtonian fluids, DNS simulations of power-law fluids are conducted in a rectangular channel for a large range of power-law indices ( = 0.5, 0.69, 0.75, 0.9, 1, 1.2). The DNS data show that the mean velocity profile in the viscous and logarithmic layers follow expressions of the form and respectively, where shows a logarithmic dependency on the flow index.Comparison with some experimental data shows the above formulation to be valid for Reynolds numbers (based on shear velocity) as high as 1000
Author Correction: New perspectives on Neanderthal dispersal and turnover from Stajnia Cave (Poland)
No full textThe Author contributions section now reads:“W.N., A.N. and S.T. designed research; A.P., M.H., W.N., S.B., M.U., A.M., H.F., M.D.B., P.S., K.S., M.Ż., A.W., A.N. and S.T. performed research; A.P., M.H., W.N., S.B., M.U., A.M., H.F., M.D.B., P.S., K.S., M.Ż., A.W., A.N. and S.T. analysed data; A.P., M.H., S.T., W.N. and S.B. wrote the paper with the collaboration of all the co-authors.
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