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Wide Span (wide + span)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Größere Spannweiten durch Flachdecken aus Konstruktions-Leichtbeton

BETON- UND STAHLBETONBAU, Issue 5 2006
Julia Stracke Dr.-Ing.
Konstruktions-Leichtbeton weist im Vergleich zu Normalbeton ein deutlich günstigeres Verhältnis von Eigengewicht zu Festigkeit auf. Es werden die hieraus resultierenden Möglichkeiten zur Optimierung von Flachdecken gerade im Hinblick auf größere Spannweiten aufgezeigt. Unter Berücksichtigung der baustoffspezifischen Eigenschaften des Leichtbetons und deren Auswirkungen auf das Tragsystem einer Flachdecke wird die Lösung einer Hohlkörperdecke entwickelt, bei der Leicht- und Normalbeton kombiniert eingesetzt werden. Damit können deutlich größere Spannweiten erreicht werden als mit herkömmlichen, nicht vorgespannten Normalbetondecken. Wide spans due to Flat Slabs with Structural lightweight aggregate Concrete Structural lightweight aggregate concrete (SLWAC) shows a much more favourable ration of dead weight to strength than normal weight concrete. The present report indicates the possibilities resulting out of this for the optimisation of flat slabs in view of wider spans. Considering the specific material properties of SLWAC and their consequences on the load bearing system of flat slabs the solution of a hollow body slab is developed in which SLWAC and normal weight concrete are used combined. Those slab systems reach clearly wider spans than conventional nonprestressed normal weight concrete slabs. [source]

Abrasiveness Testing, Quo Vadis?

GEOMECHANICS AND TUNNELLING, Issue 1 2008
A Commented Overview of Abrasiveness Testing Methods
The growing economic pressure on tunnelling and mining operations has lead to an increasing importance of investigation methods for assessing the abrasiveness of rock and soil. Such investigations can be based on a wide variety of testing procedures and standards covering a wide span of scale, ranging from real-scale tests on site to model tests with simplified tools and microscopic and chemical analyses of rocks and minerals. This paper gives an overview over some of the most important procedures, technical aspects of their application, classification of testing results and the current state of experience. Abrasivitätstest, quo vadis? Ein kommentierter Überblick über Abrasivitäts-Testverfahren Der stetig zunehmende wirtschaftliche Druck auf Tunnelbau und Rohstoffgewinnung führt zu einer steigenden Bedeutung von Untersuchungsverfahren zur Bewertung der Abrasivität von Fest- und Lockergesteinen. Derartige Untersuchungen können mit einer Vielzahl von Verfahren durchgeführt werden, die von Untersuchungen vor Ort im Realmaßstab über Modellversuche mit vereinfachten Werkzeugen bis hin zu mikroskopischen oder chemischen Untersuchungen eine weite Bandbreite an Untersuchungsmaßstäben einschließen. Der vorliegende Beitrag soll einen Überblick über die derzeit wesentlichsten Untersuchungsverfahren, versuchstechnische Aspekte, angewandte Klassifizierungsschlüssel sowie Einsatzerfahrungen mit den jeweiligen Verfahren geben. [source]

Tailoring viscoelastic and mechanical properties of the foamed blends of EVA and various ethylene-styrene interpolymers

POLYMER COMPOSITES, Issue 3 2003
I-Chun Liu
Foamed materials (EVA/ESI) have been prepared from blends of ethylene-vinyl acetate copolymer (EVA) and ethylene-styrene interpolymers (ESI) in the presence of various amounts of dicumyl peroxide (DCP). Four ESIs of different compositions were employed in this study; their styrene contents ranged from 30 to 73 wt% and their Tg ranged from ,2 to 33°C. It has been found that microcellular morphology, degree of crosslinking and expansion ratio were strongly affected by the DCP concentration and the type of ESI employed. A minimum degree of crosslinking was required for making good foams and the same degree of crosslinking could be achieved by employing a smaller amount of DCP for an EVA/ESI blend having a higher styrene content. In contrast to other EVA blends, such as EVA/LDPE, these EVA/ESI blends exhibited no existence of any optimum DCP concentration, and the , glass transition temperatures of the foams varied with the ESI type, covering a wide span from 0°C to 37°C. Therefore, it was possible to tailor the Tg of an EVA/ESI blend by choosing an appropriate type of ESI. Furthermore, by correctly tailoring the Tg, the EVA/ESI foam could be made into a rubbery material with a custom-designed damping factor. Tensile strength and modulus of the EVA/ESI foams increased generally with an increase in the styrene content, with the exception that ESIs with very low styrene content will confer on the blend a high modulus at small strain and a large elongation at break. [source]

Morphology and function of the lumbar spine of the Kebara 2 Neandertal

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2010
Ella Been
Abstract The morphology of the lumbar spine is crucial for upright posture and bipedal walking in hominids. The excellent preservation of the lumbar spine of Kebara 2 provides us a rare opportunity to observe a complete spine and explore its functionally relevant morphology. The lumbar spine of Kebara 2 is analyzed and compared with the lumbar spines of modern humans and late Pleistocene hominids. Although no size differences between the vertebral bodies and pedicles of Kebara 2 and modern humans are found, significant differences in the size and orientation of the transverse processes (L1 -L4), and the laminae (L5, S1) are demonstrated. The similarity in the size of the vertebral bodies and pedicles of Kebara 2 and modern humans suggests similarity in axial load transmission along the lumbar spine. The laterally projected (L2 -L4) and the cranially oriented (L1, L3) transverse processes of Kebara 2 show an advantage for lateral flexion of the lumbar spine compared with modern humans. The characteristic morphology of the lumbar spine of Kebara 2 might be related to the wide span of its pelvic bones. Am J Phys Anthropol 142:549,557, 2010. © 2010 Wiley-Liss, Inc. [source]