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Bearing Capacity (bearing + capacity)

Distribution by Scientific Domains

Engineering	92%
2 Other Domains	8%

Distribution within Engineering

Numerical Methods & Algorithms	55%
General & Introductory Architecture	40%

Kinds of Bearing Capacity

load bearing capacity

ultimate bearing capacity

Selected Abstracts

Tragverhalten von Flachdecken aus Stahlfaserbeton im negativen Momentenbereich und Bemessungsmodell für das Gesamtsystem

BETON- UND STAHLBETONBAU, Issue 8 2010
Julien Michels Dr.
Baustoffe; Berechnungs- und Bemessungsverfahren; Versuche Abstract Der vorliegende Artikel befasst sich mit dem Tragverhalten von Flachdecken aus Stahlfaserbeton im negativen Momentenbereich. Zugkräfte werden allein von den in der Betonmatrix eingebetteten Stahlfasern aufgenommen, letztere ermöglichen in einer Dosierung von 100 kg/m3 (1.3 % des Volumens) eine hohe Rotationsfähigkeit bei gleichzeitig hoher Tragfähigkeit. In einer ersten Phase kann anhand von Laborversuchen an Deckenausschnitten gezeigt werden, dass bei Flachdecken mit reiner Faserbewehrung und unter rotationssymetrischer Belastung kein Durchstanzen auftritt und sich ein Biegeversagen mit deutlicher Bruchlinienbildung einstellt. Neben den erhaltenen Informationen über Versagensart und -last konnte ebenfalls eine abfallende Faserwirksamkeit mit steigender Plattendicke festgestellt werden. Kombiniert mit den experimentellen Untersuchungen kann anhand nicht-linearer FE-Simulationen der Einfluss von Aussparungen bei lokalem Plattenversagen im Stützenbereich auf die Traglast beschrieben werden. Anhand der Festigkeitsstreuungen und einem semi-probabilistischen Sicherheitskonzept wird ein Sicherheitsfaktor hergeleitet, welcher es ermöglicht, einen Bemessungswert der Querschnittstragfähigkeit zu berechnen. Wegen dem experimentell festgestellten Biegeversagen wird die Bruchlinientheorie als Rechenmodell angewendet. Bearing Capacity of Steel Fiber Reinforced Concrete (SFRC) Flat Slabs in the Negative Bending Moment Area and Design Model for the Complete System The present paper deals with the bearing behaviour of steel fibre reinforced concrete (SFRC) flat slabs in the negative bending moment area. Tensile forces are carried only by steel fibers. The latter allow, due to a dosage of 100 kg/m3 (1.3% in volume), a high rotation capacity with simultaneously high bearing capacities. In a first step experimental analysis showed that under symmetrical loading no punching shear failure occurred. A bending behaviour with creation of yield lines was observed for all test specimens. Furthermore, a decreasing fibre orientation with growing plate height could be noticed. The effect of openings in the column area on the bearing capacity loss in a local failure were evaluated with the use of non-linear finite element software. Scatter in bending tensile strengths was used to calculate a safety factor by the means of a semi-probabilistic safety concept. Eventually, slab design is performed by using yield line theory. [source]

Bearing capacity of shallow foundations in transversely isotropic granular media

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2010
A. Azami
Abstract The main focus in this work is on the assessment of bearing capacity of a shallow foundation in an inherently anisotropic particulate medium. Both the experimental and numerical investigations are carried out using a crushed limestone with elongated angular-shaped aggregates. The experimental study involves small-scale model tests aimed at examining the variation of bearing capacity as a function of the angle of deposition of the material. In addition, the results of a series of triaxial and direct shear tests are presented and later employed to identify the material functions/parameters. The numerical part of this work is associated with the development and implementation of a constitutive framework that describes the mechanical response of transversely isotropic frictional materials. The framework is based on the elastoplasticity and accounts for the effects of strain localization and inherent anisotropy of both the deformation and strength characteristics. The results of numerical simulations are compared withthe experimental data. A parametric study is also carried out aimed at examining the influence of various simplifications in the mathematical framework on its predictive abilities. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Bearing capacity of two interfering footings

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2008
Jyant Kumar
Abstract By using an upper bound limit analysis in conjunction with finite elements and linear programming, the ultimate bearing capacity of two interfering rough strip footings, resting on a cohesionless medium, was computed. Along all the interfaces of the chosen triangular elements, velocity discontinuities were employed. The plastic strains were incorporated using an associated flow rule. For different clear spacing (S) between the two footings, the efficiency factor (,,) was determined, where ,, is defined as the ratio of the failure load for a strip footing of given width in the presence of the other footing to that of a single isolated strip footing having the same width. The value of ,, at S/B = 0 becomes equal to 2.0, and the maximum ,, occurs at S/B = ,Scr/B. For S/B,Scr/B, the ultimate failure load for a footing becomes almost half that of an isolated footing having width (2B + S), and the soil mass below and in between the two footings deforms mainly in the downward direction. In contrast, for S/B>Scr/B, ground heave was noticed along both the sides of the footing. As compared to the available theories, the analysis provides generally lower values of ,, for S/B>Scr/B. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Tragverhalten von Flachdecken aus Stahlfaserbeton im negativen Momentenbereich und Bemessungsmodell für das Gesamtsystem

Has Finance Made the World Riskier?

EUROPEAN FINANCIAL MANAGEMENT, Issue 4 2006
Raghuram G. Rajan
G20; G21; G22 Abstract Developments in the financial sector have led to an expansion in its ability to spread risks. The increase in the risk bearing capacity of economies, as well as in actual risk taking, has led to a range of financial transactions that hitherto were not possible, and has created much greater access to finance for firms and households. On net, this has made the world much better off. Concurrently, however, we have also seen the emergence of a whole range of intermediaries, whose size and appetite for risk may expand over the cycle. Not only can these intermediaries accentuate real fluctuations, they can also leave themselves exposed to certain small probability risks that their own collective behaviour makes more likely. As a result, under some conditions, economies may be more exposed to financial-sector-induced turmoil than in the past. The paper discusses the implications for monetary policy and prudential supervision. In particular, it suggests market-friendly policies that would reduce the incentive of intermediary managers to take excessive risk. [source]

Effect of spatial variability of cross-correlated soil properties on bearing capacity of strip footing

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 1 2010
Sung Eun Cho
Abstract Geotechnical engineering problems are characterized by many sources of uncertainty. Some of these sources are connected to the uncertainties of soil properties involved in the analysis. In this paper, a numerical procedure for a probabilistic analysis that considers the spatial variability of cross-correlated soil properties is presented and applied to study the bearing capacity of spatially random soil with different autocorrelation distances in the vertical and horizontal directions. The approach integrates a commercial finite difference method and random field theory into the framework of a probabilistic analysis. Two-dimensional cross-correlated non-Gaussian random fields are generated based on a Karhunen,Loève expansion in a manner consistent with a specified marginal distribution function, an autocorrelation function, and cross-correlation coefficients. A Monte Carlo simulation is then used to determine the statistical response based on the random fields. A series of analyses was performed to study the effects of uncertainty due to the spatial heterogeneity on the bearing capacity of a rough strip footing. The simulations provide insight into the application of uncertainty treatment to geotechnical problems and show the importance of the spatial variability of soil properties with regard to the outcome of a probabilistic assessment. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Coupled simulation of wave propagation and water flow in soil induced by high-speed trains

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 11 2008
P. Kettil
Abstract The purpose of this paper is to simulate the coupled dynamic deformation and water flow that occur in saturated soils when subjected to traffic loads, which is a problem with several practical applications. The wave propagation causes vibrations leading to discomfort for passengers and people in the surroundings and increase wear on both the vehicle and road structure. The water flow may cause internal erosion and material transport in the soil. Further, the increased pore water pressure could reduce the bearing capacity of embankments. The saturated soil is modelled as a water-saturated porous medium. The traffic is modelled as a number of moving wheel contact loads. Dynamic effects are accounted for, which lead to a coupled problem with solid displacements, water velocity and pressure as primary unknowns. A finite element program has been developed to perform simulations. The simulations clearly demonstrate the induced wave propagation and water flow in the soil. The simulation technique is applicable to railway as well as road traffic. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Bearing capacity of two interfering footings

Load-displacement and bearing capacity of foundations on granular soils using a multi-surface kinematic constitutive soil model

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2006
M. Banimahd
Abstract A finite element approach based on an advanced multi-surface kinematic constitutive model is used to evaluate the bearing capacity of footings resting on granular soils. Unlike simple elastic-perfectly plastic models, often applied to granular foundation problems, the present model realistically accounts for stress dependency of the friction angle, strain softening,hardening and non-associativity. After the model and its implementation into a finite element code are briefly discussed, the numerical difficulty due to the singularity at the footing edge is addressed. The bearing capacity factor N, is then calculated for different granular materials. The effect of footing size, shape, relative density and roughness on the ultimate bearing capacity are studied and the computed results compare very favourably with the general experimental trends. In addition, it is shown that the finite element solution can clearly represent counteracting mechanisms of progressive failure which have an important effect on the bearing capacity of granular foundations. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A homogenization method for estimating the bearing capacity of soils reinforced by columns

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2005
B. Jellali
Abstract The ultimate bearing capacity problem of a strip foundation resting on a soil reinforced by a group of regularly spaced columns is investigated in the situation when both the native soil and reinforcing material are purely cohesive. Making use of the yield design homogenization approach, it is shown that such a problem may be dealt with as a plane strain yield design problem, provided that the reinforced soil macroscopic strength condition has been previously determined. Lower and upper bound estimates for such a macroscopic criterion are obtained, thus giving evidence of the reinforced soil strong anisotropy. Performing the upper bound kinematic approach on the homogenized bearing capacity problem, by using the classical Prandtl's failure mechanism, makes it then possible to derive analytical upper bound estimates for the reinforced foundation bearing capacity, as a function of the reinforced soil parameters (volume fraction and cohesion ratio), as well as of the relative extension of the reinforced area. It is shown in particular that such an estimate is closer to the exact value of the ultimate bearing capacity, than that derived from a direct analysis which implicitly assumes that the reinforced soil is an isotropic material. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Direct assessment of structural resistance against pressurized fracture

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2003
G. Bolzon
Abstract The determination of the load bearing capacity of hydraulic structures such as dams, reservoirs and retaining walls requires the consideration of mixed-mode fracture, possibly driven by the fluid pressure, in correspondence to artificial and natural joints (or cracks, in the latter case). A friction-cohesive softening interface model with coupled degradation of normal and tangential strength is introduced here to account for the essential features of the joint behaviour; its predictive capability is assessed through extensive calculations. Alternative numerical techniques resting on the discrete-crack approach are considered, focusing on simplified approaches for the direct appraisal of the structural resistance. Comparison is made with the results of evolutionary analyses, based on a priori piecewise linearization of the interface model and on ,exact integration'. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Cyclic macro-element for soil,structure interaction: material and geometrical non-linearities

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2001
Cécile Cremer
Abstract This paper presents a non-linear soil,structure interaction (SSI) macro-element for shallow foundation on cohesive soil. The element describes the behaviour in the near field of the foundation under cyclic loading, reproducing the material non-linearities of the soil under the foundation (yielding) as well as the geometrical non-linearities (uplift) at the soil,structure interface. The overall behaviour in the soil and at the interface is reduced to its action on the foundation. The macro-element consists of a non-linear joint element, expressed in generalised variables, i.e. in forces applied to the foundation and in the corresponding displacements. Failure is described by the interaction diagram of the ultimate bearing capacity of the foundation under combined loads. Mechanisms of yielding and uplift are modelled through a global, coupled plasticity,uplift model. The cyclic model is dedicated to modelling the dynamic response of structures subjected to seismic action. Thus, it is especially suited to combined loading developed during this kind of motion. Comparisons of cyclic results obtained from the macro-element and from a FE modelization are shown in order to demonstrate the relevance of the proposed model and its predictive ability. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Lower bound limit analysis with adaptive remeshing

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 14 2005
Andrei V. Lyamin
Abstract The objective of this work is to present an adaptive remeshing procedure for lower bound limit analysis with application to soil mechanics. Unlike conventional finite element meshes, a lower bound grid incorporates statically admissible stress discontinuities between adjacent elements. These discontinuities permit large stress jumps over an infinitesimal distance and reduce the number of elements needed to predict the collapse load accurately. In general, the role of the discontinuities is crucial as their arrangement and distribution has a dramatic influence on the accuracy of the lower bound solution (Limit Analysis and Soil Plasticity, 1975). To ensure that the discontinuities are positioned in an optimal manner requires an error estimator and mesh adaptation strategy which accounts for the presence of stress singularities in the computed stress field. Recently, Borges et al. (Int. J. Solids Struct. 2001; 38:1707,1720) presented an anisotropic mesh adaptation strategy for a mixed limit analysis formulation which used a directional error estimator. In the present work, this strategy has been tailored to suit a discontinuous lower bound formulation which employs the stresses and body forces as primary unknowns. The adapted mesh has a maximum density of discontinuities in the direction of the maximum rate of change in the stress field. For problems involving strong stress singularities in the boundary conditions (e.g. a strip footing), the automatic generation of discontinuity fans, centred on the singular points, has been implemented. The efficiency of the proposed technique is demonstrated by analysis of two classical soil mechanics problems; namely the bearing capacity of a rigid strip footing and the collapse of a vertical cut. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Nonlinear FEM Simulation of Air Cushion Vehicle (ACV) Skirt Joint Under Tension Loading

NAVAL ENGINEERS JOURNAL, Issue 2 2009
JIA ZHOU
The mechanical properties of an air cushion vehicle (ACV) skirt cloth, which is a nonlinear rubber-coated fabric, are tested on a Series IX 4465 electron tension machine manufactured by Instron Company. Compared with the Mooney,Rivlin and Ogden form, the second-order Mooney,Rivlin form agrees with the model test result better. The ultimate bearing capacity of an ACV skirt joint structure is tested on a mechanical tension machine and the ultimate load is recorded manually. Then, considering the contact effect of each assembly and the large-displacement of skirt elements, a nonlinear finite element method (FEM)-based simulation process of an ACV skirt joint structure under tension loading is presented. The simulation process comprises three steps: assembly of parts, bolts' tightening, and tensioning the skirt cloth. Under these loadings, the stress distribution and deformation of the skirt cloth, and the cloth broken locations and directions are obtained. These results agree well with the test results. As for the ultimate bearing capacity of the skirt joint, the simulation result is slightly smaller than the test result. Thus, this FEM-based simulation method is proven to be reliable and relatively conservative. [source]

Verfüllung des Rodewischhafens in Hamburg , Zur Technik der Flächenaufhöhung auf Weichschichten

BAUTECHNIK, Issue 12 2005
Reiner Knies Dipl.-Ing.
Der wachsende Flächenbedarf der Wirtschaft im Hamburger Hafen einerseits und die Flächenknappheit im Ballungsraum andererseits zwingen zu einem äußerst sorgsamen Umgang mit der Ressource Fläche. Eine Optimierung bereits in Nutzung befindlicher Flächen im Hamburger Hafen mit dem Ziel, den veränderten Ansprüchen gerecht zu werden, kann auch die Auffüllung ehemaliger, teilweise mit Schlick aufgefüllter, Hafenbecken erfordern. Die Überbauung stellt aufgrund der sehr geringen Tragfähigkeit des Schlicks hohe Anforderungen an die Entwurfsbearbeitung und die Bauausführung. In diesem Beitrag werden das Tragwerkskonzept unter Verwendung besonderer Geokunststoffe sowie die dafür erforderlichen Baugrunduntersuchungen und Bemessungen vorgestellt. Die ingenieurtechnische Entwurfsbearbeitung mündete in Empfehlungen zur Anwendung der Beobachtungsmethode während der Bauausführung. Die Ergebnisse der durchgeführten Verformungsbeobachtungen werden abschließend erläutert. Backfilling of the Rodewischhafen in Hamburg , to the technology of land reclaiming on soft layers. Concerning the increasing need of store and transportation areas of the economy in Hamburg on the one hand and the surface scarceness in the population centre on the other hand force to extremely careful handling with the surface resources. An optimization of already in use present surfaces in Hamburg port with the goal of becoming changed requirements fairly more and more land reclamation activities are necessary on former harbor basins, which had been partly filled up with dredged mud. The coverage of these basins makes high requirements to the geotechnical design and the execution of construction due to the very low bearing capacity of the mud. In this contribution the load bearing concept is presented by using special geosynthetic reinforcement products as well as the necessary ground investigations and construction designs. The engineering design lead into recommendations regarding the application of the observation method during the execution of construction. Finally the results of the deformation observations are described. [source]

Zum Einfluß der Temperatur auf die Bemessung von Kühlturmschalen aus Stahlbeton

BAUTECHNIK, Issue 11 2005
Michél Bender Dipl.-Ing.
Zwangsmomente aus Temperaturgradienten haben erheblichen Einfluß auf die Bewehrungsmengen in Kühlturmschalen aus Stahlbeton. Dabei spielen nicht nur charakteristische Temperaturrandwerte und deren Kombination mit weiteren Einwirkungen eine Rolle, sondern auch die bei linearen Schnittgrößenberechnungen angenommenen Steifigkeitsreduktionen zur pauschalen Berücksichtung zwangsabbauender Rißbildung. Im Rahmen einer Sensitivitätsanalyse wird der Einfluß von Temperatureinwirkungen auf die Bemessung der Kühlturmschale vorgestellt. Basis der Parametervariation sind die spezifischen Berechnungsvorschriften der Bautechnischen Richtlinie BTR für Kühltürme (2005). Die maßgebenden rechnerischen Bemessungsszenarien werden anschließend in materiell und geometrisch nichtlinearen Analysen der Schale nachvollzogen, um die zwangsabbauende Rißbildung, den Einfluß der Temperatur auf Grenzzustände sowie Stahl- und Betonspannungswerte realistisch abzuschätzen und rechnerischen Werten gegenüberzustellen. Temperature effects on the design of cooling tower shells. Bending moments caused by temperature constraints substantially influence required reinforcement quantities in cooling tower shells. Important parameters in linear structural analyses are the extents of characteristic thermal actions and their combinations as well as global reduction factors that account for the loss of stiffness by cracking. The sensitivity to variations in temperature scenarios is presented using numerical simulations of a representative cooling tower shell and the design specifications of "BTR-Kühltürme (2005)". The characteristic design-scenarios are simulated in geometrically and materially nonlinear computations to realistically estimate the loss of stiffness by cracking, the influence of temperature effects on the ultimate load bearing capacity as well as actual extents of steel and concrete stresses. [source]

Monopilegründungen von Offshore-Windenergieanlagen , Zum Ansatz der Bettung

BAUTECHNIK, Issue 1 2005
Jürgen Grabe Univ.-Prof.
Bei der Gründung von Offshore-Windenergieanlagen mit Monopiles stellt die große Momenten- und Horizontalkraftbelastung und deren zyklisches Auftreten eine besondere Herausforderung an die Prognose der Pfahlverformungen dar. Für ein System mit beispielhaften Abmessungen, Baugrundverhältnissen und Belastungen werden die konventionellen Verfahren zur Berechnung der horizontalen Pfahltragfähigkeit und -verformung, Bettungsmodulverfahren und API-Verfahren, mit den Ergebnissen einer 3D-FE-Analyse verglichen. Es zeigt sich, daß die konventionellen Verfahren für die Prognose der Verformungen im Gebrauchszustand, also deutlich unterhalb der Grenzlast, für dieses Beispiel unzureichend sind. Die Verteilung des Bettungsmoduls über die Tiefe wird mit keinem der Verfahren zutreffend abgebildet. Des weiteren wird die Veränderung des Bettungsmoduls über mehrere Zyklen für Schwell- und Wechselbelastungen untersucht. Vor allem bei einer Schwellast wird der auf den Ausgangszustand bezogene Bettungsmodul mit jedem Zyklus verändert. Die Verschiebung des Pfahlkopfs steigt auch nach 20 Belastungszyklen noch an. Der aus der ödometrischen Steifigkeit des Bodens abgeleitete Bettungsmodul ist zur Prognose der Pfahlverformungen insbesondere bei zyklischer Last fragwürdig. Hierfür besteht insbesondere in Anbetracht der geplanten Investitionen erheblicher Forschungsbedarf. Monopile foundations for Offshore-Wind Power Plants , approach of subgrade reaction. The large moments and horizontal forces and their cyclic occurrence represent a special challenge to the prognosis of the deformations of Monopiles as a foundation of offshore wind energy plants. The conventional procedures for the computation of the horizontal pile bearing capacity and deformation, subgrade reaction procedure and API procedure, are compared with the results of a 3D-FE analysis for a system with exemplary dimensions, soil conditions and loads. It is shown that the conventional procedures for the prognosis of the deformations in the serviceability limit state, thus clearly underneath the maximum load, for this example are insufficient. The distribution of the subgrade reaction modulus over the depth is sufficiently approximated with none of these procedures. Moreover the change of the subgrade reaction modulus is investigated for several cycles swelling and alternated loads. The modulus of subgrade reaction, referred to the initial pile position, changes especially under swelling loads for each loading cycle. The displacement of the pilehead still increases after 20 cycles. The modulus of subgrade reaction derived from the oedometric soil stiffness does not produce an accurate prognosis of the pile deformation particularly for cyclic loads. For this purpose further investigations are necessary. [source]

Q- und R-Matten aus Kunststoff für Bewehrungsaufgaben in der Geotechnik

BAUTECHNIK, Issue 9 2004
Georg Heerten Dr.-Ing.
Wachsende Güterströme und Warenverkehre im Zentrum eines wachsenden Europas und zunehmender Warenaustausch als Folge der Globalisierung der Weltwirtschaft stellen erhebliche Anforderungen an den Erhalt und Ausbau leistungsfähiger Infrastruktursysteme (Straße, Schiene, Wasserstraße). Nachhaltigkeitskonzepte bei der Bautätigkeit und Finanzierungsprobleme der öffentlichen Auftraggeber sind aktuelle Randbedingungen, denen mit Geokunststoff-Bauweisen optimal Rechnung getragen werden kann. Es können neben den technischen auch die ökonomischen und ökologischen Vorteile , Baukosten sparen, Baustoffressourcen schonen , parallel genutzt werden. Eine Stützwand als "Bewehrte-Erde-Konstruktion" kann ganz erheblich kostengünstiger als eine Stahlbeton-Stützmauer hergestellt werden. Die Ertüchtigung von wenig tragfähigen Böden mit flächig angeordneten Bewehrungslagen und/oder pfahlartigen geokunststoffummantelten Bodensäulen vermeidet umfangreichen Bodenaustausch, spart Kosten, verhindert umfangreichen Transport von Bodenmassen mit LKWs. Hierdurch werden knappe Baustoffressourcen wie Sand und Kies geschont sowie eine z. T. erhebliche Entlastung örtlicher Verkehrswege bewirkt. Q and R mats made of synthetics for reinforcement functions in the field of geotechnics. An increasing flow of goods in a growing central Europe, resulting from the globalisation of the world economy, makes high demands on the maintenance and development of an efficient infrastructure (road, railway, waterway). Sustainability concepts for the construction activities and funding problems of the contracting authorities are current boundary conditions which can be accommodated optimally with geosynthetic construction methods. At the same time, besides the technical advantages, the economical and ecological advantages can be used too , saving of construction costs and taking care of building materials resources. A retaining wall as "Reinforced-Earth-Structure" can be constructed at much lower cost than a retaining wall made of reinforced concrete. The improvement of subsoils with low bearing capacity, by using reinforcing layers in the area and/or soil columns similar to piles wrapped with geosynthetics, avoids a considerable exchange of soil, saves costs and avoids substantial soil transports by trucks. Thus, care is taken on rare building materials resources like sand and gravel and the traffic routes are partly released to a high extent. [source]

Experimentelle und numerische Untersuchungen zum Tragverhalten von Stahlbetondecken mit kugelförmigen Hohlkörpern

BETON- UND STAHLBETONBAU, Issue 6 2010
Marcin Abramski Dr.-Ing.
Abstract Massive Flachdecken erweisen sich in Hoch- und Industriebau häufig als insgesamt überlegenes Deckensystem. Die hohe Eigenlast dieser Decken kann ihren Anwendungsbereich jedoch einschränken. Eine sinnvolle Abhilfe schafft dann die Integration von Hohlkörpern in der neutralen Zone, weil hierdurch eine spürbare Gewichtsreduktion eintritt. Neben der Eigenlast wird auch der Verbrauch der unter ökologischen Gesichtspunkten wesentlichen Ressourcen Betonstahl und Zement deutlich verringert. Die Hohlräume beeinflussen vor allem die Querkrafttragfähigkeit solcher Decken. Vier Versuchsserien, die mit kugelförmigen Hohlkörperdecken des Systems "cobiax" durchgeführt wurden, werden in diesem Beitrag beschrieben. Aus den Versuchen wird ein Abminderungsfaktor zur Beschreibung des Querkrafttragverhaltens abgeleitet, der auch in die kürzlich erteilte allgemeine bauaufsichtliche Zulassung des Deckensystems eingegangen ist. Die Nachrechnung der Versuche mit der Finite-Elemente-Methode zeigt eine gute Übereinstimmung von Numerik und Experiment, so dass in der Weiterentwicklung Parameterstudien auf dieser Grundlage zur Ergänzung von Versuchen hilfreich sein werden. Experimental and Numerical Investigation of the Bearing Behaviour of Hollow Core Slabs Massive flat slabs have proven to be the most appropriate ceiling system for structural and industrial engineering. However the high dead load of these slabs might reduce their field of application. This problem can be solved by void formers that are placed in the neutral zone. These block-outs cause a noticeable reduction of weight. Furthermore, the masses of ecologically important resources like reinforcement steel and cement can be reduced as well. The shear bearing capacity is significantly influenced by these block-outs. This article describes four test series with spherical void former floors of the system "cobiax". A reduction factor for the shear bearing capacity is derived from these tests. That factor was also introduced in the technical approval for this slab system which has been issued recently. A comparison to a calculation with the finite element method shows that the numerical results and the results of the tests are quite similar. In future research, parameter studies based on the finite element method might be helpful additional to further tests. [source]

Tragverhalten von Verbundbauteilen aus bewehrtem UHFB und Stahlbeton

BETON- UND STAHLBETONBAU, Issue 8 2009
Cornelius Oesterlee Dipl.-Ing.
Baustoffe; Bauwerkserhaltung/Sanierung; Bauausführung; Versuche Abstract Ultra-Hochleistungs-Faserbetone (UHFB) eignen sich aufgrund ihrer hohen Festigkeiten, des hohen Verformungsvermögens und der geringen Permeabilität zur Verbesserung und Instandsetzung bestehender Betonbauten. Mit dünnen Schichten von bewehrtem UHFB, die auf bestehende Stahlbetonbauteile aufgetragen werden, können der Tragwiderstand und die Gebrauchstauglichkeit deutlich gesteigert werden. In einer umfangreichen Versuchsreihe wurden die Eigenschaften von mit zusätzlich zu den Fasern auch mit Stabstahl bewehrtem UHFB untersucht. Die Bewehrung des UHFB mit Stabstählen ist vorteilhaft, um den Verfestigungsbereich des UHFB zu erweitern, seinen Tragwiderstand zu erhöhen und die Streuung seiner mechanischen Eigenschaften zu reduzieren. Zur Bewehrung können hoch- oder niederfeste Stähle mit unterschiedlichen Oberflächenstrukturen zum Einsatz kommen. Abschließend werden zwei Anwendungen vorgestellt. Structural Behaviour of Composite Elements Combining Reinforced Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) and Reinforced Concrete Due to their high strengths, high deformability and low permeability Ultra-High Performance Fibre-Reinforced Concretes (UHPFRC) are suitable for the improvement and rehabilitation of existing concrete structures. Thin layers of reinforced UHPFRC that are applied to existing concrete members, increase both the load bearing capacity and the serviceability. By comprehensive experimental studies the behaviour of UHPFRC with additional bar reinforcement was investigated. The reinforcement of UHPFRC is advantageous in order to increase the strain hardening capacity of UHPFRC, its load bearing capacity and to reduce the scatter of its mechanical properties. Low or high strength steel grades with various surface characteristics can be used as reinforcement of UHPFRC. Finally two on site applications are presented. [source]

Rißbildung in turmartigen Tragwerken: Schleuderbetonmast versus Stahlbetonschornstein

BETON- UND STAHLBETONBAU, Issue 7 2005
Piotr Noakowski Prof. Dr.-Ing.
Im Zeitalter des Mobilfunks dienen viele turmartige Bauwerke als Antennenträger. Viele davon stellen die besonders dafür konzipierten Schleuderbetonmaste sowie alte, entsprechend nachgerüstete Schornsteine dar. Manche dieser Tragwerke weisen auffällige Vertikalrisse auf, deren Auswirkung auf die Tragfähigkeit begutachtet werden muß. Bei dieser Aufgabe muß in Betracht gezogen werden, daß das im Erfahrungsbereich liegende Rißverhalten normaler Betontragwerke nur bedingt auf Schleuderbetontragwerke übertragbar ist. In diesem Sinne befaßt sich der vorliegende Beitrag mit der Erforschung der Unterschiede im Rißverhalten der hochfesten Schleuderbetonmaste gegenüber dem der niederfesten Betonschornsteine. Die entsprechenden Untersuchungsergebnisse wurden mit der Rißnachweismethode aus DIN V 1056, DIN EN 13084 und CICIND Model Code gewonnen und stellen einen wichtigen Teil der Qualitätssicherung von turmartigen Tragwerken dar. Crack Formation in Tower like Structures: Mast of centrifugal concrete vs. chimney of normal concrete Numerous tower like structures are used as antenna carriers in the age of cell phones. Most of them are for this aim designed masts of high strength concrete and old purposely equipped chimneys. Some of those structures show conspicuous vertical cracks which may affect the wind bearing capacity and thus, have to be assessed. In connection with this task the fact must be considered that the experiences with crack behavior of normal concrete structures are only conditionally valid for masts of centrifugal concrete. Regarding all this the differences in crack behavior of high strength masts and low strength chimneys are addressed in this paper. The investigation results were gained by the computation method from DIN V 1056, DIN EN 13084 and CICIND Model Code and represent an important part of the quality assurance of the tower like structures. [source]

Kurze Verankerungslängen mit Rechteckankern

BETON- UND STAHLBETONBAU, Issue 1 2004
Josef Hegger Prof. Dr.-Ing.
Abstract In der Zulassung Z-15.6-204 [1] des Deutschen Instituts für Bautechnik werden Halfen HDB-E-Anker mit rechteckigen Köpfen als Endverankerung in Rahmenknoten und Konsolen für die Anwendung gemäß DIN 1045-1 und DIN 1045 geregelt. Durch die schlupfarme Verankerung der Zuggurtbewehrung ergeben sich Vorteile hinsichtlich der konstruktiven Durchbildung, der Tragfähigkeit und der Bauausführung. In diesem Beitrag werden die Zulassungsregelungen erläutert. Rectangular Anchors with short Anchorage Length The technical approval Z-15.6-204 [1] of the Deutsches Institut für Bautechnik gives design rules for the use of Halfen HDB-E-headed studs in exterior-beam-column-joints and corbels. The anchorage with headed studs is characterized by a negligible slippage of the reinforcement and is advantageous regarding the load bearing capacity, the detailing and the handling on site. This paper describes the design rules, devided from comprehensive experimental and numerical investigations [2]. [source]

A study of the bone healing kinetics of plateau versus screw root design titanium dental implants

CLINICAL ORAL IMPLANTS RESEARCH, Issue 3 2009
Gary Leonard
Abstract Objective: This study was designed to compare the bone healing process around plateau root from (PRF) and screw root from (SRF) titanium dental implants over the immediate 12 week healing period post implant placement. Material and methods: 32PRF and 32SRF implants were placed in 8 beagle dogs at 12, 8, 5 and 3 weeks prior to enthanisation using a bilaterally balanced distribution. Undecalcified ground sections were prepared from the biopsies taken and histometric measurements of bone implant contact (BIC) and bone area fraction occupancy (BAFO) were made on the middle 5 mm portion of each 8 mm implant root length. Results: The analysis showed that although measurements of bone to implant contact (BIC) and bone area fraction occupancy (BAFO) tended to be greater for the SRF implants at all four time points, the differences in measurements between implant types did not reach statistical significance (P=0.07, P=0.06). The effect of time on BIC and BAFO was found to be strongly significant for both implant types thus indicating a statistically significant increase in BIC and BAFO overall with time (P=0.004, P=0.002). Furthermore, both PRF and SRF implants behaved similarly over time with measurements of BIC and BAFO progressing in parallel. Histomorphologic analysis of these sections demonstrated the prominent role of woven bone (callus) in the bone healing process around PRF implants. Conclusion: The results can be interpreted to indicate a comparable development of secondary stability for both PRF and SRF implant designs. However, as these parameters reflect the structural connection between implant and bone and not the functional properties of the bone to implant interface, they cannot be regarded as comprehensive measures of osseointegration. This particularly relevant given the reduced load bearing capacity of woven bone. [source]