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Load Capacity (load + capacity)
Selected AbstractsDurchstanzversuche mit Bewehrung mit hochfestem Verbund, innovative Traganalysen und BemessungsansätzeBETON- UND STAHLBETONBAU, Issue 8 2007Richard Rojek Prof. Dr.-Ing. Im vorliegenden Aufsatz wird über Durchstanzversuche berichtet, bei denen in die Stahlbeton-Versuchsplatten als Durchstanzsicherung Bewehrung mit hochfestem Verbund eingebaut wurde. Die Versuchsergebnisse zeigen, dass mit diesem System sehr gute Tragfähigkeiten erreicht werden. Aus den Rissbildern der nach den Versuchen aufgeschnittenen Versuchsplatten konnten interessante Rückschlüsse auf die Tragwirkung des Systems gezogen werden. Ein Vergleich dieser Rissbilder mit denjenigen von Versuchsplatten mit Doppelkopfankern als Durchstanzsicherung zeigt im Detail deutliche Unterschiede im Tragverhalten. Die Analyse der Versuchsergebnisse führt außerdem zu neuartigen Erkenntnissen über die Tragmechanismen im durchstanzgefährdeten Auflagerbereich von Stahlbetonplatten, die auch die Grundlage für einen Vorschlag bieten, die bestehenden Bemessungsregeln zu modifizieren. Slab Punching Tests with Reinforcement with High-Strength Bond In this paper there is given an account of punching tests, in which the tested concrete slabs were reinforced against punching by reinforcement with high-strength bond. The test results show that very good load capacities are obtainable. The pictures of the cracks, which were to be seen after the test slabs were cut up, gave interesting conclusions about the carrying behaviour of the system. Comparing these cracks with those of test slabs with double headed punching anchors clearly shows the differences of the carrying behaviours. The analysis of the test results also gives new knowledge about the carrying mechanisms at the critical punching zone of reinforced concrete slabs, which also build a basis for a proposal how to modify the existing design rules. [source] Full scale experiments for evaluating theoretical fire wall modelsFIRE AND MATERIALS, Issue 6 2004P. Clancy Abstract The aim of the research described in this paper was to provide experimental results for the evaluation of theoretical models for predicting the behaviour and time-to-failure of loadbearing and non-loadbearing wood framed walls in fire. References for thermal and mechanical properties of wood and gypsum board are given to provide comprehensive input for the evaluation of theoretical wall models. The scope of the research involved full-scale uninsulated cavity walls with well-controlled clearly known conditions including initial ambient vertical load capacity for benchmarking the reduction in capacity and stiffness, rotational stiffness of supports, eccentricity of vertical load, elastic moduli of wood and gypsum board in compression, stiffness of slip between gypsum board and studs and end stud effects. The experiments were repeated and they demonstrated that the controls led to high consistency in the results despite the inherent large variability of the mechanical properties of wood. The results include temperature distributions, initial vertical load capacity, load-deflection plots and times-to-failure. The results show that the temperatures in the studs are approximately uniform until all the moisture is vaporized. Thermal properties of wood will not vary significantly for consistent density, moisture content and species of wood. The main structural actions that should be modelled for different loading regimes are deduced. Copyright © 2004 John Wiley & Sons, Ltd. [source] Inclined load capacity of suction caissonsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2003C. P. Aubeny Abstract A simplified method of analysis for estimating lateral load capacity of suction caisson anchors based on an upper bound plasticity formulation is presented. The simplification restricts the analysis to caissons in uniform and linearly varying undrained strength profiles; nevertheless, its computational efficiency permits quick evaluation of a number of parameters affecting load capacity. The validity and limitations of the simplified formulation are demonstrated through comparisons to more rigorous finite element solutions. A series of sensitivity studies demonstrate the effects of various soil conditions and loading parameters. Copyright © 2003 John Wiley & Sons, Ltd. [source] A molecular dynamics simulation of air adsorption in single-walled carbon nanotube bundlesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2008Víctor Rojas Cervellera Abstract The physisorption of air in single-walled carbon nanotubes (SWNTs) is studied employing molecular dynamics. The effect of the nanotube diameter in the gas adsorption capacity of SWNT bundles has been investigated using (10,0), (15,0), and (20,0) SWNTs finding an increasing load capacity. The O2:N2 ratio in the nanotube bundles is analyzed in detail as well, comparing it to that in the gaseous bulk. The air contained in the carbon nanostructures has a larger content in O2 than the bulk air, thus providing a possible application of carbon nanotubes as molecular filters. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Surface roughness effects on thermo-hydrodynamic lubrication of journal bearings lubricated with bubbly oilLUBRICATION SCIENCE, Issue 1 2006A. M. A. El-Butch In this paper, the combined effect of surface roughness and bubbles content on the hydrodynamic performance of journal bearings is studied. In the analysis, it is assumed that the bearing and shaft surfaces are covered with homogeneous isotropic roughness, the air bubbles are evenly distributed through the lubricant and the bubble size is very small. The modified Reynolds equation governing the pressure generation in the bearing gap for compressible fluid is solved simultaneously with the energy equation. Temperature and pressure distributions, coefficient of friction, bearing load capacity and attitude angle as affected by surface roughness, bubble content and some bearing parameters are presented. Results showed that the bearing load carrying capacity is higher at higher values of average roughness and higher bubble content as a direct consequence of the higher pressure values attained, and the average roughness and the bubbles content had no significant effect on the attitude angle. Copyright © 2006 John Wiley & Sons, Ltd. [source] Concept for a New Hydrodynamic Blood Bearing for Miniature Blood Pumps,ARTIFICIAL ORGANS, Issue 10 2004Thomas Kink Abstract: The most crucial element of a long-term implantable rotary blood pump is the rotor bearing. Because of heat generation and power loss resulting from friction, seals within the devices have to be avoided. Actively controlled magnetic bearings, although maintenance-free, increase the degree of complexity. Hydrodynamic bearings for magnetically coupled rotors may offer an alternative solution to this problem. Additionally, for miniature pumps, the load capacity of hydrodynamic bearings scales slower than that of, for example, magnetic bearings because of the cube-square-law. A special kind of hydrodynamic bearing is a spiral groove bearing (SGB), which features an excellent load capacity. Mock-loop tests showed that SGBs do not influence the hydraulic performance of the tested pumps. Although, as of now, the power consumption of the SBG is higher than for a mechanical pivot bearing, it is absolutely contact-free and has an unlimited lifetime. The liftoff of the rotor occurs already at 10% of design speed. Further tests and flow visualization studies on scaled-up models must demonstrate its overall blood compatibility. [source] Die neue Schneelastnorm DIN 1055-5, kritisch hinterfragtBAUTECHNIK, Issue 10 2009Wolfgang Schwind Dipl.-Ing. (FH) Die neue Schneelastnorm DIN 1055-5:7/2005 brachte vor allem in den höhergelegenen Orten der Zone 3 erhebliche Erhöhungen der Schneelast, die bis zum Zweifachen der bisher anzusetzenden Belastung reicht. Auch die neuen Formeln für die Belastung von aneinandergereihten Dächern, von Shed- und Tonnendächern sowie die Behandlung von Höhensprüngen und Trauflasten erscheint problematisch. In diesem Beitrag wird versucht, Unstimmigkeiten der Norm aufzuzeigen. The current snow load standard DIN 1055-5 , a critical review. The current snow load standard DIN 1055-5:7/2005 caused a considerable increase of snow load, particularly in more elevated areas located in zone 3. It doubles the amount of snow load capacity , compared to the old standard. The new equations for calculating snow loads for adjacent roofs, shed roofs and arched roofs as well as the handling differences in altitude and gutter load seems problematic. This paper tries to show the inconsistencies of current standard. [source] Beton unter hohen Temperaturen , eine Frage der TunnelsicherheitBETON- UND STAHLBETONBAU, Issue 2 2006Konrad Bergmeister Prof. Dipl.-Ing. Die Sicherheit in den Tunnels wird einerseits durch das Verhalten der Benützer und andererseits durch die Konstruktion und Ausstattung bestimmt. Neben der Modellierung des Verhaltens und der Anwendung von Sicherheitstheorien in Tunnel gilt es, organisatorische und erzieherische Maßnahmen in der Planungs-, Ausführungs- und Betriebsphase zu setzen. Durch die extreme Hitzeentwicklung können die Einbauten und das Tunneltragwerk beschädigt werden. Dabei kann es zu Betonabplatzungen (spalling) und zum Ablösen von Betonstücken bzw. Verankerungen kommen. In diesem Beitrag werden unterschiedliche Spritzbetone -experimentell unter hohen Temperaturen untersucht. Dabei zeigt sich, daß die Dichte und die Porenverteilung sowie die Zugkapazität der Betonformulierung von ausschlaggebender Bedeutung sind. Concrete exposed to high Temperatures , a safety Issue of tunnels The safety of tunnels is related to the behaviour of the users as well as to the construction and the equipment, which may be damaged due to heat impact. Concrete spalling decreases the effects of corrosion protection and the bonding of the reinforcement, and the load capacity is also diminished. Predictions about possible concrete spalling and failure mechanism often are based on experimental research. The crucial parameters for concrete spalling are the gas pressure in the pores, the physical properties e. g. water absorption at 20 °C and after 1000 °C and the mechanical resistance. In a full scale fire test in a highway tunnel there have been investigated various shotcrete mixtures. Pore size and distribution have been determined with the Mercury Intrusion (MIP) Porosimeter, whereas the permeability was calculated using the results of the MIP at different temperatures. It could be shown, that the moisture in the pore system and the physical and chemical adsorpted water in the matrix as well as in the aggregates evaporates under external increase of temperature and thus leading to higher pressure. Fire resistant shotcrete for use in tunnel shells should exhibit a certain volume of open pores in order to equalize the vapour pressure. [source] Adsorption of SO2 on Activated Carbon for Low Gas ConcentrationsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007P. Zhang Abstract Adsorption experiments of SO2 on activated carbon has been carried out for low concentrations (about 100,ppm) at room temperature (15 to 33,°C) with varying humidity in the air. The breakthrough curves show that at high relative humidity or relative higher SO2 concentration, the load capacity increases with respect to temperature. The humidity of the air is also of benefit to the load capacity of SO2. When an adsorption process is interrupted and the activated carbon is kept closed for a while, the SO2 concentration at the exit of a fixed-bed adsorber is similar to that of the fresh activated carbon and begins at a very low value. It appears that the sorption potential has been refreshed after the storage period. Analysis of desorption experiments by simultaneous thermal analysis combined with mass spectrometry (MS) after loading, shows that the physisorbed SO2 and H2O are desorbed at low temperatures. At higher temperatures, the MS peak of SO2 and H2O occur at the same time. Compared with desorption immediately after loading, after one day, the desorption peak due to the physisorbed SO2 disappears. From this, it can be concluded that the refreshment of the loading capacity of the activated carbon after storage is mainly due to a change in the nature of the SO2 from a physisorbed state to a chemisorbed form. The same mechanism leads to a continuous refreshment of the sorption potential by means of a chemical reaction during the adsorption process. [source] | |||||||||||||