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Load-carrying Capacity (load-carrying + capacity)

Distribution by Scientific Domains

Engineering	100%

Selected Abstracts

Die Tragfähigkeit verleimter Brettschichtholzbinder in Abhängigkeit von der Temperatureinwirkung

BAUTECHNIK, Issue 6 2006
Horst Falkner Univ.-Prof.
Bei einem Bauvorhaben wurde als Tragstruktur für die Glasfassade eine Holzleimstruktur eingesetzt. Da nicht auszuschließen war, daß die Temperatur der Fassadenhölzer unter Sonneneinwirkung eine Größe von 60 °C erreichen konnte, wurde der Einfluß der Temperatur auf die Tragfähigkeit der Leimverbindung untersucht. Hierzu wurden aus dem Bauvorhaben einige Proben entnommen und am iBMB (Institut für Baustoffe, Massivbau und Brandschutz) der TU Braunschweig unter Variation der Bauteiltemperatur nach DIN 52186 geprüft. Dabei ergab sich bis zu einer Temperatur von 30 °C keine Veränderung der Tragfähigkeit. Bei höherer Temperatureinwirkung von 80 °C betrug die Tragfähigkeit nur noch 30% derjenigen unter Normaltemperatur. Hier wurde der Bruch durch ein Versagen der Leimfuge eingeleitet. Load-carrying capacity of glued laminated wood girders under temperature influence. For a building project, a load carrying structure for the glass façade consisting of glued laminated wood was chosen. As it could not be excluded that the temperature of the wood under solar radiation might reach up to 60 °C, the temperature influence on the load carrying capacity of the glued laminated wood had to be investigated. Samples were taken from the wooden structure and tested at the iBMB (Institute for Building Materials, Concrete Construction and Fire Protection) under temperature variation according to DIN 52186. No reduction in the load carrying capacity was observed for temperatures up to 30 °C. For a higher temperature of 80 °C a reduction of the load carrying capacity of 70% was observed. The fracture was induced by the failure of a glued joint. [source]

Failure Mechanism of Deformed Concrete Tunnels Subject to Diagonally Concentrated Loads

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2009
Wei He
Based on the experimental findings, an extended discussion is carried out to select a rational compressive model for concrete that represents the dominant failure modes of deformed concrete tunnels. Three main dominant final failure modes are described: structural failure due to the plastic rotation of softening hinges, tensile failure caused by localized cracks, and material failure due to concrete deterioration. A parametric analysis of the material properties of concrete shows that the compressive strength of concrete has a dominant effect on the load-carrying capacity, although the compressive fracture energy of concrete remarkably influences the post-peak deformation behavior of the tunnel. Moreover, the soil pressure, which is regarded as a distributed external load, plays an important role in controlling the final failure modes and the deformation behavior of concrete tunnels. The size effect on the load-carrying capacities of different-sized concrete tunnels is also discussed based on the numerical simulations. [source]

Tribological performances of heterocyclic-containing ether and/or thioether as additives in the synthetic diester

LUBRICATION SCIENCE, Issue 3 2009
Peipei Liang
Abstract The load-carrying capacity, wear and friction properties of 2-octoxyl methylthio-benzothiazole (DEOY) and 2-dodecylthio methylthio-benzothiazole (DEMB) added to a synthetic lubricant (diester) were evaluated using a four-ball test machine. The results indicate that the two compounds added to the diester possess good load-carrying capacities and excellent anti-wear and friction reduction properties. The thermal stability of the two compounds under nitrogen atmosphere was investigated by thermogravimetric analysis (TGA). It was found that the compounds DEOY and DEMB possess excellent thermal stability. The surface topography of the rubbed surface was investigated with scanning electron microscopy, the elemental chemical nature of the anti-wear films generated on steel counterface were investigated with X-ray photoelectron spectroscopy. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Failure Mechanism of Deformed Concrete Tunnels Subject to Diagonally Concentrated Loads

A design-variable-based inelastic hysteretic model for beam,column connections

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2008
Gun Jin Yun
Abstract This paper presents a design-variable-based inelastic hysteretic model for beam,column connections. It has been well known that the load-carrying capacity of connections heavily depends on the types and design variables even in the same connection type. Although many hysteretic connection models have been proposed, most of them are dependent on the specific connection type with presumed failure mechanisms. The proposed model can be responsive to variations both in design choices and in loading conditions. The proposed model consists of two modules: physical-principle-based module and neural network (NN)-based module in which information flow from design space to response space is formulated in one complete model. Moreover, owing to robust learning capability of a new NN-based module, the model can also learn complex dynamic evolutions in response space under earthquake loading conditions, such as yielding, post-buckling and tearing, etc. Performance of the proposed model has been demonstrated with synthetic and experimental data of two connection types: extended-end-plate and top- and seat-angle with double-web-angle connection. Furthermore, the design-variable-based model can be customized to any structural component beyond the application to beam,column connections. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Cyclic behavior of laterally loaded concrete piles embedded into cohesive soil

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2008
Rabin Tuladhar
Abstract Modern seismic design codes stipulate that the response analysis should be conducted by considering the complete structural system including superstructure, foundation, and ground. However, for the development of seismic response analysis method for a complete structural system, it is first imperative to clarify the behavior of the soil and piles during earthquakes. In this study, full-scale monotonic and reversed cyclic lateral loading tests were carried out on concrete piles embedded into the ground. The test piles were hollow, precast, prestressed concrete piles with an outer diameter of 300,mm and a thickness of 60,mm. The test piles were 26,m long. Three-dimensional (3D) finite element analysis was then performed to study the behavior of the experimental specimens analytically. The study revealed that the lateral load-carrying capacity of the piles degrades when subjected to cyclic loading compared with monotonic loading. The effect of the use of an interface element between the soil and pile surface in the analysis was also investigated. With proper consideration of the constitutive models of soil and pile, an interface element between the pile surface and the soil, and the degradation of soil stiffness under cyclic loading, a 3D analysis was found to simulate well the actual behavior of pile and soil. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Lower-bound limit analysis by using the EFG method and non-linear programming

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2008
Shenshen Chen
Abstract Intended to avoid the complicated computations of elasto-plastic incremental analysis, limit analysis is an appealing direct method for determining the load-carrying capacity of structures. On the basis of the static limit analysis theorem, a solution procedure for lower-bound limit analysis is presented firstly, making use of the element-free Galerkin (EFG) method rather than traditional numerical methods such as the finite element method and boundary element method. The numerical implementation is very simple and convenient because it is only necessary to construct an array of nodes in the domain under consideration. The reduced-basis technique is adopted to solve the mathematical programming iteratively in a sequence of reduced self-equilibrium stress subspaces with very low dimensions. The self-equilibrium stress field is expressed by a linear combination of several self-equilibrium stress basis vectors with parameters to be determined. These self-equilibrium stress basis vectors are generated by performing an equilibrium iteration procedure during elasto-plastic incremental analysis. The Complex method is used to solve these non-linear programming sub-problems and determine the maximal load amplifier. Numerical examples show that it is feasible and effective to solve the problems of limit analysis by using the EFG method and non-linear programming. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A general model for porous medium flow in squeezing film situations

LUBRICATION SCIENCE, Issue 2 2010
Mohamed Nabhani
Abstract The present paper deals with a numerical investigation of the hydrodynamic lubrication of a porous squeeze film between two circular discs. To this purpose, the thin film (reduced) Navier Stokes equations and a generalised porous medium model are solved. The numerical results show that the effect of the porous disc is to reduce the lubricating properties of the fluid film. This effect is increased during the squeezing action. In addition, it is shown that the film pressure, the load-carrying capacity and the velocity field based only on the Darcy model are predicted higher than those obtained from the generalised porous medium model. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Effect of wear on EHD film thickness in sliding contacts

LUBRICATION SCIENCE, Issue 1 2006
R. Michalczewski
Abstract A theoretical solution to the elastohydrodynamic (EHD) lubrication problem in sliding contacts, which takes into consideration the effect of the change in shape of the gap due to wear on the load-carrying capacity, is presented. The model of such a contact is based on assumptions of Grubin and Ertel (von Mohrenstein). The resultant dimensionless Reynolds and film profile equations have been solved numerically for a number of cases with several values of thickness of the worn layer. Iteration of the EHD film thickness is performed by means of the secant method. Values of the calculated dimensionless film thickness are presented as a function of dimensionless wear. The conclusions concern the influence of the linear wear on the film thickness in heavily loaded sliding contacts. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A study of the synergistic effect of a triazine-dithiocarbamate derivative with tcp in vegetable oil

LUBRICATION SCIENCE, Issue 4 2005
Z. Y. He
Abstract A novel, potential ashless S,N-style additive, 2-(N,N-dibutylamino)-4,6-bis-(dibutyldithiocarbamate)-1,3,5-triazine (DBTT), was synthesised and its synergistic tribological effect with a traditional additive, tricresyl phosphate (TCP), in rape seed oil was evaluated using a four-ball tester. The results show that the load-carrying capacity of the vegetable oil could be improved greatly by the presence of the TCP and/or DBTT additives; at certain mass ratios TCP and DBTT show a good synergistic effect in improving the tribological performance of the base oil. The elemental composition and chemical nature of antiwear films generated at a steel interface were investigated using Kevex energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. Scanning electron microscopy was also used to study the rubbed surface morphology. It was found that FeS, organosulphur compound, sulphate, phosphate, and nitrogen-containing compounds were present in the complex boundary lubrication film. [source]

An ESCA study of the effectiveness of antiwear and extreme-pressure additives based on substituted phosphorodithioate derivatives, and a comparison with ZDDP

LUBRICATION SCIENCE, Issue 2 2001
M. C. Jain
Ashless substituted dithiophosphoric acid derivatives (ADPs) are a new generation of multifunctional additives with promising antiwear (AW) and extreme-pressure (EP) characteristics. Three such additives synthesised in the authors' laboratory have been evaluated for their AW and EP properties by standard four-ball friction and wear tests. The friction-reducing properties of these additives were compared with those of a commercial zinc dialkyldithiophosphate (ZDDP). It was found that the phosphorodithioate compounds studied here possessed excellent AW/EP properties. Their AW characteristics were found to be comparable to those of ZDDP at low loads. However, at higher loads they show inferior AW characteristics in comparison to ZDDP. Nevertheless, ADP derived from cashew nut shell oil had a higher load-carrying capacity than ZDDP. The mechanism of the AW and EP behaviour exhibited by the different additives was investigated using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and scanning electron microscopy (SEM) of the worn surfaces formed during friction. XPS and AES analyses of the worn surfaces reveal that the tribochemical film formed on the ADP-tested surfaces consisted mainly of metal phosphates and only a small amount of metal sulphides, even though the ADPs contained twice the number of sulphur atoms than phosphorus atoms. The ZDDP-tested surface showed a mixture of metal sulphides and metal phosphates. Alkylamino substitution appeared to have no significant effect on the AW/EP properties of the additive. XPS and AES analyses also revealed that the tribochemical film formed on an ADP-tested surface was thicker than that present on the ZDDP-tested surface at low loads, whereas at higher loads the reverse was true. The higher weld load obtained for the blend containing cashew nut shell oil-derived ADP is attributed to the thicker adsorbed reaction film formed on the surface due to the long alkyl groups present in the original additive structure. Short-chain alkyl groups, however, form only a thin adsorbed layer, which may get rubbed off during the friction at high load. The low sulphide formation on ADP-tested surfaces was attributed to the absence of any metal atom in the additive, which would help in the formation of metal sulphides during tribofragmentation and further tribochemical reactions. [source]

Zur Druck-Zug-Festigkeit von Stahlbeton und stahlfaserverstärktem Stahlbeton

BETON- UND STAHLBETONBAU, Issue 8 2009
Ekkehard Fehling Prof. Dr.-Ing.
Versuche; Bemessungs- und Berechnungsverfahren Abstract Während die Druckfestigkeit des Betons durch gleichzeitig wirkenden Querdruck gegenüber der einaxialen Druckfestigkeit erheblich gesteigert werden kann, führen Querzugbeanspruchung und Rissbildung zu einer Abminderung der Tragfähigkeit. Dies gilt für unbewehrten Beton und Stahlbeton gleichermaßen. In den einschlägigen Regelwerken finden sich hierzu international sehr unterschiedliche Bemessungsansätze, wobei die vorgesehenen Abminderungsbeiwerte für denselben Anwendungsfall um das bis zu Zweifache differieren. Die Frage der Druck-Zug-Festigkeit von Stahlbeton wurde in den vergangenen 40 Jahren von zahlreichen Wissenschaftlern untersucht. Ihre Ergebnisse sind allerdings zum Teil ebenso widersprüchlich wie die aktuelle Normensituation. Basierend auf eigenen experimentellen Untersuchungen sowie einer kritischen Auswertung und Einordnung als richtungweisend angesehener, früherer Versuchsreihen wird ein Vorschlag zur Abminderung der Druckfestigkeit des gerissenen Stahlbetons entwickelt. Erstmals wird dabei auch der Einfluss einer Faserzugabe in Kombination mit Stabstahlbewehrung berücksichtigt. Ein Vergleich mit den in DIN 1045-1, CEB-FIP Model Code 1990, Eurocode 2 und ACI Standard 318-05 angegebenen Bemessungsregeln zeigt, dass allein DIN 1045-1 die in den Versuchen beobachtete maximale Abminderung der Druckfestigkeit durch Querzug und Rissbildung zum Teil erheblich unterschätzt, so dass eine konservative Auslegung der Tragwerke nicht immer sichergestellt ist. Biaxial Compression-Tension-Strength of Reinforced Concrete and Reinforced Steel Fibre Concrete The compressive strength of concrete can be substantially increased in relation to uni-axial compressive strength by transverse compression acting at the same time. In contrast, transverse tension and cracking lead to a reduction of the load-carrying capacity. This holds true for plain concrete as well as for reinforced concrete. In international standards very different calculation rules can be found on this subject, whereby the provided reductions differ up to a factor of two for the same application. The question of biaxial compression-tension-strength of reinforced concrete was examined in the past 40 years by numerous scientists. Their results are, however, partially contradictory in the same way as the current standard situation. Based on own experimental investigations as well as on a critical review and classification of former test series regarded as trend-setting, a proposal for the reduction of the compressive strength of cracked reinforced concrete is developed. For the first time, also the influence of fibres in addition to bar reinforcement is considered thereby. A comparison with the calculation rules in DIN 1045-1, CEB-FIP Model Code 1990, Eurocode 2, and ACI Standard 318-05 shows, that exclusively DIN 1045-1 underestimates sometimes substantially the maximum reduction of the compressive strength by transverse tension and cracking observed in the tests, so that a conservative design of structures cannot always be ensured. [source]