186,351 research outputs found
200 Years old cauchy concept pointed the route to optimizing concrete porosimetry in Virtual reality: Heron’s fountain 18
No full textThe solution of a technical problem is in many cases potentially available however probably somewhat hidden in the literature. At least, research engineers in concrete technology have the tendency not to search for it but to come up with their own ideas. Unfortunately, not always of the same standard as guaranteed by the original source. Interestingly, many powerful theoretical concepts relevant for concrete technology are of stereological nature, although in many cases (much) older than stereology itself (Stroeven and Hu, 2006; Stroeven et al., 2009). With the development of stereology as a science since the foundation of the society for stereology in 1963, old roots became apparent: stereology avant la lettre. As a concrete technologist the second author of this fountain enjoyed several playful discoveries over the years that in some cases constituted old but reliable milestones along the route to solving popular problems in our field. Baron Augustin-Louis Cauchy (21 August 1789 – 23 May 1857) formed such a milestone. He was a French mathematician reputed as a pioneer of analysis. He was one of the first to state and prove theorems of calculus rigorously. Of the extensive oeuvre of Cauchy, two formulas – almost two centuries old – are of significance for concrete technology (and other branches of science) (Cauchy, 1882; Stroeven and Hu, 2006)Applied Mechanic
Methodology of modeling fiber reinforcement in concrete elements
No full textThis paper’s focus is on the modeling methodology of (steel) fiber reinforcement in concrete. The orthogonal values of fiber efficiency are presented. Bulk as well as boundary situations are covered. Fiber structure is assumed due to external compaction by vibration to display a partially linear planar structure (Stroeven-concept), which can even be simplified in many practical situations to a partially planar system. The two unknown parameters can be experimentally assessed in a single vertical projection image by orthogonal line scanning. Several boundary conditions are distinguished and the practical case of a thin SFRC plate is evaluated. Advantages over a practical but very approximate proposal in the open literature are shown.Structural EngineeringCivil Engineering and Geoscience
Numerical assessment of concrete damage: procedures and pitfalls
No full textpeer reviewedThe paper focuses on the quality of predicting the damage characteristics of the loaded engineering structure by subjecting section images of cores supposedly drawn from the concrete of the structure to quantitative image analysis by sweeping test lines. Automation of this data acquisition stage is shown, generally leading to information that is biased to an unknown degree. This is accomplished mathematically and graphically according to Underwood. When the Stroeven/Saltikov (S/S)-concept of a partially linear-planar model for damage is accepted and (four-connexity) digitization is accomplished in a direction adjusted to the prevailing orientation direction of the cracks, the paper shows that orthogonal observations in vertical sections are sufficient for the unbiased assessment of total crack length per unit of area (2D), or specific crack surface area (3D), also when digitized images are employed. This is possible in situations where (uniaxial) compressive or tensile stresses dominate. The crack orientation distribution is however always biased when determined on digitized images in an automated set up when pixel directions are not compensated for, such as by the quantified S/S-concept of damage
Cordilleran ice sheet glacial cycle simulations continuous variables
No full textThese data contain a subset of time-dependent glacier model output variables:
Reference:
J. Seguinot, I. Rogozhina, A. P. Stroeven, M. Margold, and J. Kleman. Numerical simulations of the Cordilleran ice sheet through the last glacial cycle, The Cryosphere, 10(2):639–664, 10.5194/tc-10-639-2016, 2016.
File names:
ciscyc4.{10km|5km}.{forcing}.{ex.1ka|ts.10a}.nc
Horizontal resolution:
10km: 10 km horizontal resolution
5km: 5 km horizontal resolution
Temperature forcing:
epica: EPICA ice core temperature forcing
grip: GRIP ice core temperature forcing
ngrip: NGRIP ice core temperature forcing
odp1012: ODP 1012 ocean core temperature forcing
odp1020: ODP 1020 ocean core temperature forcing
vostok: Vostok ice core temperature forcing
Variable types:
ex.1ka: spatial diagnostics every thousand years
ts.10a: scalar time-series every ten years
Data format:
The data use compressed netCDF format. For quick inspection I recommend ncview. Spatial diagnostics (*.ex.1ka.nc) can be converted to GeoTIFF (and other GIS formats) e.g. using GDAL:
gdal_translate NETCDF:filename.nc:variable -b band filename.variable.band.tif
The list of variables (subdatasets) can be obtained from ncdump or gdalinfo. The band number equals 120 minus the age in ka. Band information can be displayed with:
gdalinfo NETCDF:filename.nc:variable
Variable long names, units, PISM configuration parametres and additional information are contained within the netCDF metadata.</p
How to measure path length?
No full textPath length measuring is a relevant engineering problem. Leonardo Da Vinci designed for the military appropriate equipment, the podometer, to do so. Modern equipment such as step meters and map meters are quite similar to Da Vinci?s design, despite geometrical statistical - stereological - methods based on theorems of Cauchy and Buffon that were potentially available for a long period of time for doing a better job. The theorems have moreover been applied earlier for the engineering purposes indicated in this paper. Even Saltikov?s reintroduction for quantitative image analysis purposes in 1945 was ignored. Gradually, the last half of a century, stereological methods became more popular in concrete technology. Nevertheless, the stereology-based global averaging operation required to make the step from materials technology to engineering properties is inherent to making errors, as the literature demonstrates. The methodological framework has been described in earlier papers by this author as to path length measurements in sections of cracked concrete and on X-ray images of steel fibre reinforced concrete (SFRC). By laying side by side in this paper the direct engineering approach (from Da Vinci to map meter) and the science (stereology)-based approaches, the profit in economy and reliability can nevertheless be stressed. Particularly the element of geometric averaging based on simple mathematical-statistical notions is highlighted, because the literature reflects still major violations to these scientific principles. Three-dimensional information in the indicated fields of materials engineering is also readily obtained, provided proper sampling is guaranteed.Structural EngineeringCivil Engineering and Geoscience
SPACE Approach to Concrete's Space Structure and its Mechanical Properties
No full textStructural properties of particulate materials can be described in densities of the particle packing, more generally denoted as particle composition. Obviously, this global measure does not offer information on the way particles are mutually arranged in space. This is associated with particle configuration. This terminology and the associated categories of material behaviour that rely on either one of these extremes of structural properties are elaborated in this paper. The range of such properties will be between structure-insensitive ones, like mass or stiffness (Young's modulus), and structure-sensitive properties like crack initiation and tensile strength. The establishment of an experimental basis for the dependence of a mechanical property on certain structural features (and the associated micro-mechanical properties) would require extensive, cumbersome and complicated testing: mechanical testing for defining the very property, quantitative (section) image analysis and stereological three-dimensional assessment of the relevant structural features. 'Realistic' simulation of material structure by computer would therefore offer an interesting alternative. This paper introduces the SPACE system (Software Package for the Assessment of Compositional Evolution) as the most recent development in this field. It has been developed to assess the composition as well as configuration characteristics of dense random packing situations in opaque materials. This paper presents an introduction to the system and will thereupon highlight by means of illustrative examples of typical applications on different levels of the microstructure the system's capabilities. Although only a single application can be presented in this framework, they all concern areas of major engineering interest.Structural MechanicsCivil Engineering and Geoscience
Low-cycle compression fatigue of reinforced concrete structures
No full textPaper reports on experiments performed in the low-cycle compression fatigue domain, considering two relatively high upper load levels and several lower ones. Two frequency levels were emphasized, i.e. 17.5 Hz and 0.175 Hz. An overview is given of characteristics of mechanical behaviour and of the state of damage close to fracture. Particular attention is given to the larger amplitude case of 17.5 Hz because of an order of magnitude drop in the number of cycles to fracture. The normal process of damage evolution is sketched as well as the process for this specific case, where damage evolution due to stress release is initiating premature fracture. Underlying mechanisms are outlined.Structural EngineeringCivil Engineering and Geoscience
Stereology of concrete reinforced with short steel fibres
No full textMechanical tests on steel fibre reinforced concrete (SFRC) can only be interpreted on the basis of a structural analysis. Stereological tools are available for that purpose. Results of recent investigations will be presented, revealing quite complex characteristics of the fibre dispersion in the matrix. Stereological reasoning can additionally be employed to solve theoretical problems. Such problems are encountered when the constitutive relationships for this type of omposites are formulated. Brief reference will be made to typical results obtained in this way.Structural MechanicsCivil Engineering and Geoscience
Micro- and Macromechanical Behaviour of Steel Fibre Reinforced Mortar in Tension
No full textStructural MechanicsCivil Engineering and Geoscience
Poissons' Ratio in Uniaxial Tension and Anticlastic Bending of Micro Concrete and Perspex
No full textStevin LaboratoryCivil Engineering and Geoscience
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