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Concrete Structures (concrete + structure)

Distribution by Scientific Domains

Engineering	87%

Selected Abstracts

A Risk-Cost Optimized Maintenance Strategy for Corrosion-Affected Concrete Structures

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2007
Chun-Qing Li
It is also observed that some severely deteriorated concrete structures survive for many years without maintenance. This raises the question of why and how to maintain corrosion-affected concrete structures, in particular in the climate of an increasing scarcity of resources. The present article attempts to formulate a maintenance strategy based on risk-cost optimization of a structure during its whole service life. A time-dependent reliability method is employed to determine the probability of exceeding a limit state at each phase of the service life. To facilitate practical application of the formulated maintenance strategy, an algorithm is developed and programmed in a user-friendly manner with a worked example. A merit of the proposed maintenance strategy is that models used in risk assessment for corrosion-affected concrete structures are related to some of the design criteria used by practitioners. It is found in the article that there exists an optimal number of maintenances for cracking and delamination that returns the minimum total cost for the structure in its whole life. The maintenance strategy presented in the article can help structural engineers, operators, and asset managers develop a cost-effective management scheme for corrosion-affected concrete structures. [source]

Bücher: Computational Modelling of Concrete Structures.

BAUTECHNIK, Issue 2 2009
By G. Meschke, H. Mang, N. Bicanic, R. de Borst
No abstract is available for this article. [source]

Buchbesprechung: Management of Deteriorating Concrete Structures (2008).

BETON- UND STAHLBETONBAU, Issue 12 2008
Von George Sommerville.
No abstract is available for this article. [source]

Fugenausbildung und -abdichtung bei wasserundurchlässigen Bauwerken aus Beton: Neue Regelwerke setzen Maßstäbe

BETON- UND STAHLBETONBAU, Issue 12 2004
Rainer Hohmann Prof. Dr.-Ing.
Fugen stellen bei wasserundurchlässigen Bauwerken aus Beton häufig eine Schwachstelle dar. Sie erfordern die besondere Beachtung des Planers und der Ausführenden. Eine fachgerechte Handhabung sowohl durch den Planer als auch durch den Ausführenden ist eine entscheidende Voraussetzung für eine funktionierende Abdichtung. Neue Regelwerke, wie die DAfStb-Richtlinie "Wasserundurchlässige Bauwerke aus Beton" und die DIN V 18197 "Abdichten von Fugen in Beton mit Fugenbändern" geben Hinweise, wie Abdichtungssysteme richtig einzusetzen und zu dimensionieren sind. In dem Beitrag wird auf die neuen Regelwerke und die wesentlichen Regelungen für die Abdichtung eingegangen. Joint Design and Joint Sealing in Waterproof Concrete Structures , New Regulations are setting New Sealing Standards In many cases joints in structures of waterproof concrete turn out to be a weak point. For this reason they demand the care and attention of the designer and the contractor. A professional application as well by the planner as by the contractor is a decisive precondition for an effective operation of the joint sealing. New regulations like DAfStb-code: "Waterproof concrete structures" and the German standard DIN V 18197: "Sealing of joints in concrete with waterstops" give details how the sealing systems should be used and dimensioned correctly. This article goes into the details of the new regulations and the basic rules for sealing. [source]

Test method for concrete spalling using small electric furnace

FIRE AND MATERIALS, Issue 4 2010
Ren Zhao
Abstract Concrete spalling can cause severe damage to concrete structure when exposed to fire. The spalling mechanisms are not very well understood. For the testing of spalling, full-scale structural members should be used, as spalling tests are sensitive to size effects. Full-scale testing in large furnace is costly and is not suitable for testing large number of concrete mixture trials. The standard and hydrocarbon fire time,temperature curves have rapid temperature rise during the initial phase. This temperature rise requires a gas furnace with high heating capacity and cannot be generated by electric muffle furnace commonly available in many laboratories. This paper presents a method to carry out spalling test in small-scale specimens with exposure to rapid temperature rise using a commonly available electric furnace in the laboratories. The tests are based on 150,mm diameter cylinders that are laterally confined to simulate full-scale structural members. The cylinder surface is exposed to rapid temperature rise by exposing through vertical and/or horizontal holes in pre-heated small electric furnace. Some unconfined 100,mm diameter cylinders were also exposed horizontally to test the performance of confinement. The paper shows that the hydrocarbon fire and standard fire exposure can be simulated by manipulating the exposure location of the surface of the concrete cylinder. Ordinary Portland cement concrete cylinders with different strengths were tested and different spalling patterns were observed. The spalling patterns matched the test results from a gas furnace fire test simulating the fire curves. The tests demonstrated that the method is an effective and convenient technique to predict the spalling risk of a concrete. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Coupled damage and plasticity modelling in transient dynamic analysis of concrete

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 1 2002
Fabrice Gatuingt
Abstract In a concrete structure subjected to an explosion, for example a concrete slab, the material is subjected to various states of stress which lead to many modes of rupture. Closer to the explosive, a state of strong hydrostatic compression is observed. This state of stress produces an irreversible compaction of the material. Away from the zone of explosion, confinement decreases and the material undergoes compression with a state of stress, which is slightly triaxial. Finally, the compression wave can be reflected on a free surface and becomes a tensile wave, which by interaction with the compression wave, produces scabbing. We present, in this paper, a model aimed at describing these three failure modes. It is based on visco-plasticity and rate dependent damage in which a homogenization method is used in order to include the variation of the material porosity due to compaction. The model predictions are compared with several experiments performed on the same concrete. Computations of split Hopkinson tests on confined concrete, a tensile test with scabbing, and an explosion on a concrete slab are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Nonlinear Damping Identification in Precast Prestressed Reinforced Concrete Beams

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2009
P. Franchetti
Integrated static and dynamic experiments were carried out on three precast PRC beam specimens. The static loading induced different levels of damage to the beams. At each damage level, impulsive loading was applied to the beams and the free vibration response was measured. The dynamic response data were processed using different methods including the multi-input multi-output (MIMO) curve fitting and the Hilbert transform techniques. A strong correlation is observed between the level of concrete damage (cracks) and the amount of nonlinear energy dissipation that can be modeled by means of quadratic damping. The nonlinear damping can be extracted from the free vibration response for each vibration mode. The proposed method is suited for quality control when manufacturing precast PRC members, and can be further extended for in situ detection of damage in concrete structures under ambient vibration. [source]

A Risk-Cost Optimized Maintenance Strategy for Corrosion-Affected Concrete Structures

Influence of dynamic soil,structure interaction on the nonlinear response and seismic reliability of multistorey systems

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2007
Armando Bárcena
Abstract A set of reinforced concrete structures with gravitational loads and mechanical properties (strength and stiffness) representative of systems designed for earthquake resistance in accordance with current criteria and methods is selected to study the influence of dynamic soil,structure interaction on seismic response, ductility demands and reliability levels. The buildings are considered located at soft soil sites in the Valley of Mexico and subjected to ground motion time histories simulated in accordance with characteristic parameters of the maximum probable earthquake likely to occur during the system's expected life. For the near-resonance condition the effects of soil,structure interaction on the ductility demands depend mainly on radiation damping. According to the geometry of the structures studied this damping is strongly correlated with the aspect ratio, obtained by dividing the building height by its width. In this way, for structures with aspect ratio greater than 1.4 the storey and global ductility demands increase with respect to those obtained with the same structures but on rigid base, while for structures with aspect ratio less than 1.4 the ductility demands decrease with respect to those for the structures on rigid base. For the cases when the fundamental period of the structure has values very different from the dominant ground period, soil,structure interaction leads in all cases to a reduction of the ductility demands, independently of the aspect ratio. The reliability index , is obtained as a function of the base shear ratio and of the seismic intensity acting on the nonlinear systems subjected to the simulated motions. The resulting reliability functions are very similar for systems on rigid or on flexible foundation, provided that in the latter case the base rotation and the lateral displacement are removed from the total response of the system. Copyright © 2006 John Wiley & Sons, Ltd. [source]

An efficient three-dimensional solid finite element dynamic analysis of reinforced concrete structures

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2006
K. V. Spiliopoulos
Abstract Most of the finite element analyses of reinforced concrete structures are restricted to two-dimensional elements. Three-dimensional solid elements have rarely been used although nearly all reinforced concrete structures are under a triaxial stress state. In this work, a three-dimensional solid element based on a smeared fixed crack model that has been used in the past mainly for monotonic static loading analysis is extended to cater for dynamic analysis. The only material parameter that needs to be input for this model is the uniaxial compressive strength of concrete. Steel bars are modelled as uniaxial elements and an embedded formulation allows them to have any orientation inside the concrete elements. The proposed strategy for loading or unloading renders a numerical procedure which is stable and efficient. The whole process is applied to two RC frames and compared against existing experiments in the literature. Results show that the proposed approach may adequately be used to predict the dynamic response of a structure. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Earthquake-induced interaction between adjacent reinforced concrete structures with non-equal heights

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2005
Chris G. Karayannis
Abstract The influence of the structural pounding on the ductility requirements and the seismic behaviour of reinforced concrete structures designed to EC2 and EC8 with non-equal heights is investigated. Special purpose elements of distributed plasticity are employed for the study of the columns. Two distinct types of the problem are identified: Type A, where collisions may occur only between storey masses; and Type B, where the slabs of the first structure hit the columns of the other (72 Type A and 36 Type B pounding cases are examined). Type A cases yielded critical ductility requirements for the columns in the pounding area mainly for the cases where the structures were in contact from the beginning of the excitation. In both pounding types the ductility requirements of the columns of the taller building are substantially increased for the floors above the highest contact storey level probably due to a whiplash behaviour. The most important issue in the pounding type B is the local response of the column of the tall structure that suffers the hit of the upper floor slab of the adjacent shorter structure. In all the examined cases this column was in a critical condition due to shear action and in the cases where the structures were in contact from the beginning of the excitation, this column was also critical due to high ductility demands. It can be summarized that in situations of potential pounding, neglecting its possible effects leads to non-conservative building design or evaluation that may become critical in some cases. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Preface to computational mechanics of concrete and concrete structures

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7-8 2004
Nenad Bi
No abstract is available for this article. [source]

Numerical modelling for earthquake engineering: the case of lightly RC structural walls

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7-8 2004
J. Mazars
Abstract Different types of numerical models exist to describe the non-linear behaviour of reinforced concrete structures. Based on the level of discretization they are often classified as refined or simplified ones. The efficiency of two simplified models using beam elements and damage mechanics in describing the global and local behaviour of lightly reinforced concrete structural walls subjected to seismic loadings is investigated in this paper. The first model uses an implicit and the second an explicit numerical scheme. For each case, the results of the CAMUS 2000 experimental programme are used to validate the approaches. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Modelling of elastoplastic damage in concrete due to desiccation shrinkage

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2002
F. Bourgeois
We present a numerical modelling of elastoplastic damage due to drying shrinkage of concrete in the framework of mechanics of partially saturated porous media. An elastoplastic model coupled with isotropic damage is first formulated. Two plastic flow mechanisms are involved, controlled by applied stress and suction, respectively. A general concept of net effective stress is used in take into account effects of capillary pressure and material damage on stress-controlled plastic deformation. Damage evolution depends both on elastic and plastic strains. The model's parameters are determined or chosen from relevant experimental data. Comparisons between numerical simulations and experimental data are presented to show the capacity of model to reproduce mains features of concrete behaviour under mechanical loading and during drying shrinkage of concrete. An example of application concerning drying of a concrete wall is finally presented. The results obtained allow to show potential capacity of proposed model for numerical modelling of complex coupling processes in concrete structures. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Computational mechanics of the steel,concrete interface,

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 2 2002
M. R. Ben Romdhane
Abstract Concrete cracking in reinforced concrete structures is governed by two mechanisms: the activation of bond forces at the steel,concrete interface and the bridge effects of the reinforcement crossing a macro-crack. The computational modelling of these two mechanisms, acting at different scales, is the main objective of this paper. The starting point is the analysis of the micro-mechanisms, leading to an appropriate choice of (measurable) state variables describing the energy state in the surface systems: on the one side the relative displacement between the steel and the concrete, modelling the bond activation; on the other hand, the crack opening governing the bridge effects. These displacement jumps are implemented in the constitutive model using thermodynamics of surfaces of discontinuity. On the computational side, the constitutive model is implemented in a discrete crack approach. A truss element with slip degrees of freedom is developed. This degree of freedom represents the relative displacement due to bond activation. In turn, the bridge effect is numerically taken into account by modifying the post-cracking behaviour of the contact elements representing discrete concrete cracks crossed by a rebar. First simulation results obtained with this model show a good agreement in crack pattern and steel stress distribution with micro-mechanical results and experimental results. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Depassivation of steel reinforcement in case of pitting corrosion: detection techniques for laboratory studies

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2009
L. Bertolini
Abstract Methods for service life prediction of reinforced concrete structures exposed to chloride-bearing environments require, amongst other parameters, the knowledge of the chloride threshold for pitting corrosion initiation (Clth). Nowadays, although the main factors influencing the chloride threshold are well known, it is often difficult to quantify a value of the chloride threshold, partly because of its intrinsic high variability, and partly because of the different test methods that have been used to measure it. All the experimental tests rely on the detection of steel depassivation and simultaneous measurement of chloride content or steel potential. This paper deals with the methods that can be used to detect steel depassivation in relation with the determination of the chloride threshold. Tests in concrete-pore-simulating solutions as well as tests in concrete will be considered, and advantages and limitations will be discussed. [source]

Potential mapping technique for the detection of corrosion in reinforced concrete structures: Investigation of parameters influencing the measurement and determination of the reliability of the method

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2009
Y. Schiegg
Abstract The potential distribution around a corrosion site in concrete was modeled by means of a simple mathematical model for a rod-shaped anode. Based on these calculations the influencing parameters and the limits of the potential mapping technique were determined. They demonstrate that the location of anodes depends on the anode length, the concrete coverage, and the measuring grid. Moreover small anodes with less than 1 cm length are virtually impossible to localize. Investigations on concrete elements without reinforcing steel showed that heterogeneous water content and chloride distribution can result in potential differences of up to 150 mV on the concrete surface. This effect was related to the streaming potential and the diffusion overpotential in the concrete. In order to determine the reliability of the potential mapping technique in the field application, the concrete on a tunnel wall was removed after the measurement of the potential distribution and the corrosion loss of the steel was determined. It was found that all corrosion sites with more than 2 mm material loss were detected by the potential mapping technique. Only some smaller corrosion sites were not found. Based on this investigation, the applicability of the potential mapping technique for detecting corrosion sites was confirmed. The observed high reliability of the potential mapping technique can be explained by a combination of the heterogeneous wetting of the concrete, the inhomogeneous contamination with chloride, and the macrocell formation. [source]

Monitoring the corrosion and remediation of reinforced concrete on-site: An alternative approach

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2005
N. Birbilis
Abstract Difficulties associated with the interpretation of site data collected over long periods of time from commonly used electrochemical corrosion monitoring techniques often make it difficult to assess the corrosion of reinforcing steel. An alternative approach for the interpretation of data is proposed, based on a model of the quality of passive film upon the steel surface. This model leads to a representation of the corrosion state by means of the relationship, over a long period of time, of the corrosion potential and the logarithm of the Linear Polarization Resistance, since both are functions inter alia of corrosion rate. It is shown that for the reinforced concrete panels tested, data points representing this relationship closely fitted a family of results; allowing the development of a "monitoring control diagram", MCD. The MCD reveals that for a fixed geometry and experimental conditions, a relationship between the corrosion potential and polarization resistance of steel exists, facilitating a useful monitoring tool for assessment of both the corrosion and remediation of reinforced concrete structures. Particular emphasis is placed on the latter in this work. [source]

One fragmentation procedure for brittle material cracking

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2006
S. H. Reese
Realistic modeling of 3D fragmentation procedures with minimal incorporation of restrictions to the crack path is still a challenge in modern computational engineering simulations. The presented approach is used to model failure and cracking in concrete structures, applying an explicit finite element integration scheme. Within this model the Strong Discontinuity Approach (SDA) is used to handle the failure process until the material is fully damaged. At stage an adaptive refinement technique is incorporated in ordner to introduce real cracks which are suitable for DEM / FEM coupling or contact formulations. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

MORTAR STUDIES TOWARDS THE REPLICATION OF ROMAN CONCRETE

ARCHAEOMETRY, Issue 6 2009
HELEN GOLDSWORTHY
The use of strong and durable materials is one essential ingredient leading to the survival of many monumental Roman concrete structures. Replicated concrete mortars with different lime to pozzolan ratios, encompassing the range likely to have been used by the Romans, have been studied here to determine their relative compressive strengths as a function of time. This has been supplemented by the use of the scanning electron microscope to delve into the structure and composition of the binders formed within the strongest and weakest mortars, leading to a deeper understanding of the reasons for the differences in compressive strength. [source]

Beitrag zur Berechnung der Durchbiegung von Stahlbetonbauteilen und Kritik an der ÖNORM B 4700

BAUTECHNIK, Issue 5 2008
Zivilingenieur für Bauwesen i. R. Friedrich Schäfer Dipl.-Ing.
Im Folgenden wird eine Berechnung der Durchbiegung des Stahlbetons angegeben. Diese unterscheidet sich gegenüber früheren Durchbiegungsberechnungen der ÖNORM B4700 , Stahlbetontragwerke (EUROCODE-nahe Berechnung, Bemessung und konstruktive Durchbildung) , und ÖNORM B4200/8 dadurch, dass unter anderem Versuchsresultate berücksichtigt und die Vorgänge wirklichkeitsnah erfasst werden. Die nach den oben genannten ÖNORMEN berechneten und überhöhten Tragwerke in Österreich sind nach Jahrzehnten noch überhöht. Dies kann unter anderem als Indiz für eine falsche Durchbiegungsberechnung angesehen werden. Es wird daher empfohlen, die in der ÖNORM B4700 , Stahlbetontragwerke , angegebene Berechnungsmethode der Durchbiegung des Stahlbetons erstens aus der Norm zu entfernen, da diese, wie wir zeigen werden, nicht richtig ist; zweitens sich wie in der DIN 1045 auf eine Angabe der Schlankheiten zu beschränken und eventuell die Durchbiegung nach den hier angegebenen Überlegungen zu berechnen und drittens diese dem Bauingenieur zu überlassen und auf diese Weise auch die Qualen der Bauingenieure zu beenden. Da die Normen auch den Stand der Technik darstellen und eingehalten werden müssen, stellt dies zusätzlich ein rechtliches Problem dar. Wie gezeigt wird, beinhaltet die angegebene Methode der Berechnung der Durchbiegung in der ÖNORM B4700 schon im Ansatz schwere Gedankenfehler und falsche Voraussetzungen. A contribution to the calculation of the deflection of reinforced concrete members. Stated below you will find a calculation of the deflection of reinforced concrete. It differs from former calculations of the deflection according to the Austrian standard ÖNORM B4700 , reinforced concrete structures (EUROCODE-based calculation, dimensioning and constructive design) , and Austrian standard ÖNORM B4200/8 in that it takes into consideration, among others, the results of tests and represents the processes realistically. The load-bearing structures in Austria which were calculated according to the above-mentioned Austrian standards and feature a precamber still have a camber after decades. This may be regarded, among others, as an indication for an incorrect calculation of the deflection. It is therefore requested that the calculation method for the deflection of reinforced concrete specified in ÖNORM B4700 , reinforced concrete structures , firstly, be removed from this standard because it is not correct, as will be shown; secondly, restrict itself to stating the slendernesses, as is the case with DIN 1045, and to calculate the deflection according to the considerations contained in this paper, for example; and thirdly, to leave the calculation method to the structural engineers, which would also put an end to their anguish. Since the standards also represent the state of the art and have to be observed, this additionally poses a legal problem. As will be shown, the method for calculating the deflection according to ÖNORM B4700 contains serious errors of thought and wrong presuppositions in its basic approach, already. [source]

Zur Bemessung von Betonbauteilen auf Basis der Coulombschen Hypothese , Interpretation und Verifizierung experimenteller Daten

BAUTECHNIK, Issue 1 2007
Leonid Bussler Dr.-Ing.
Im Beitrag wird gezeigt, wie man die Coulombsche mehrachsige Betonfestigkeit im Zusammenhang mit der Spannungs-Dehnungs-Linie benutzt. Eine Durchführung der Differenzspannungsanalyse bei ein- und dreiachsigem symmetrischen Druck erlaubt, nicht ausreichende experimentelle Daten bei unsymmetrischem zwei- und dreiachsigen Druck richtig zu interpretieren. Dabei läßt sich eine reale und nichtproportionale Belastung in Konstruktionen besonders bei positivem mehrachsigen Druck auf die einfache proportionale Belastung ohne jegliche negative Folgen zurückführen. Dimensioning of concrete structures on the basis of Coulomb's hypothesis , Interpretation and verification of experimental data. The article shows the use of the multiaxial Coulomb concrete strength combined with the stress-strain diagram. The differential tensions analysis in case of uniaxial and three-axle symmetrical compression allows interpreting properly the insufficient experimental data in case of biaxial and three-axle asymmetrical compression. At the same time a real and non-proportional load in constructions especially in case of multiaxial compression can be attributed to a simple proportional load without any consequences. [source]

Dynamische Zustandsbewertung einer Verbundbrücke: Beobachtung äußerer und nichtlinearer Einflüsse auf die modalen Eigenschaften

BETON- UND STAHLBETONBAU, Issue 8 2010
Volker Bungard Dipl.-Ing.
Bauwerksüberwachung; Dynamische Einwirkungen/Erdbeben; Brückenbau; Versuche Abstract Bei der Anwendung dynamischer Untersuchungsmethoden zur Zustandsbewertung von Ingenieurbauwerken aus Stahl- und Spannbeton sowie Verbundbau spielen Veränderungen von Rand- und Umweltbedingungen auf die modalen Parameter eine wesentliche Rolle. Während man diese im Laborexperiment weitest gehend überwachen bzw. ausschließen kann, sind sie bei in-situ Versuchen nur schwer zu kontrollieren. Am Beispiel einer Verbundbrücke soll demonstriert werden, welche Größenordnung die Veränderung von Randbedingungen (z. B. Veränderung von anregenden Kräften) und Umwelteinflüsse (z. B. Temperatur) auf die dynamischen Parameter einer in-situ Struktur haben können. Die Größenordnung dieser Veränderungen wird mit Veränderungen, die aus wirklichen Strukturschäden resultieren können, verglichen und bewertet. Dynamic Condition Assessment of a Composite Bridge: Investigation of External and Nonlinear Influences on the Modal Properties Using dynamic investigation methods to assess the state of civil constructions like reinforced and prestressed concrete structures as well as composite structures, changes in boundary conditions and environmental influences play a decisive role. Under laboratory conditions it is possible to control respectively to exclude these influences but it is not always possible to control and to exclude them when testing in-situ. By means of dynamic measurements which are conducted on a composite bridge, possible changes in dynamic properties resulting from changes in the amplitude of the excitation force and resulting from changes in the temperature conditions are demonstrated. The dimension of these changes is compared with changes in modal properties resulting from real structural defects and structural damages. [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]

Das Druckgurtmodell für Stahlbetonbauteile

BETON- UND STAHLBETONBAU, Issue 8 2009
Der nachfolgende Beitrag erscheint aus Anlass des 60.
Berechnungs- und Bemessungsverfahren; Versuche Abstract In den vergangenen Jahren wurden verschiedene auf die Bemessung von Stahl- und Spannbetonbauteilen ausgerichtete theoretische Modelle entwickelt. Heute stehen das Zuggurtmodell, das Modell der gerissenen (Steg-)Scheibe und das Druckgurtmodell zur Verfügung, auf deren Grundlage Verformungsverhalten und Tragwiderstände umfassend beurteilt werden können. Auf das Druckgurtmodell wird im vorliegenden Beitrag detailliert eingegangen. Es berücksichtigt die Festigkeits- und Duktilitätssteigerung durch eine Umschnürungsbewehrung sowie die bruchmechanisch begründete Entfestigung des Betons und die damit einhergehende Verformungslokalisierung. Auf der Grundlage neuerer Versuchsergebnisse können für die komplexen Interdependenzen zwischen diesen Effekten plausible Beziehungen angegeben werden. Die mithilfe des Druckgurtmodells gewonnenen Erkenntnisse sind für die Baupraxis von Bedeutung: Das Verhalten von auf Druck beanspruchten Bauteilen (z. B. Druckplatten von Brückenquerschnitten, Stützen) lässt sich zuverlässig erfassen; darüber hinaus ergeben sich wichtige Hinweise für die konstruktive Durchbildung. Compression Chord Model for Structural Concrete In recent years, several theoretical models have been developed with the scope on the design of reinforced and prestressed concrete structures. Today, the tension chord model, the cracked membrane model and the compression chord model are available, with which the deformation behaviour as well as ultimate loads can be determined. In the present contribution the compression chord model is discussed in detail. The model takes the increase of strength and ductility due to a confining reinforcement into account and considers the softening as well as the localisation of deformations accompanying the fracture of concrete. On the basis of new test results plausible relations for the complex interdependencies between these effects are found. The results of the compression chord model are relevant for practical applications: The behaviour of compressed members (e.g. in bridge girders or columns) can be assessed reliably; moreover, hints for the detailing of reinforcement can be deduced. [source]

Verformungsvorhersage von vorgespannten und nicht vorgespannten Betonbauteilen

BETON- UND STAHLBETONBAU, Issue 6 2009
Wolfgang Krüger Prof. Dr.-Ing. habil.
Baustoffe; Berechnungs- und Bemessungsverfahren; Spannbeton Abstract Wie vergleichende Untersuchungen zeigen, führt eine Begrenzung der Verformung auf der Grundlage des Schlankheitsnachweises, wie er nach DIN 1045-1 bei Stahlbetonbauteilen möglich ist, nicht immer zu dem gewünschten Erfolg. In diesen Fällen und bei Spannbetonkonstruktionen ist grundsätzlich ein Nachweis der Verformungen erforderlich. Ausgehend von allgemeinen Betrachtungen zum Nachweis der Bauteilverformungen, werden wesentliche materialseitige Einflüsse auf die Verformungsvorhersage diskutiert. Es wird deutlich, dass eine genaue Berechnung der Verformung nur bedingt möglich ist. Im Anschluss wird für die tägliche Berechnungspraxis ein Näherungsansatz zur Vorhersage der Verformung bewehrter Betonbauteile formuliert. Im Rahmen von vergleichenden Betrachtungen wird die Genauigkeit des entwickelten Näherungsansatzes abgeschätzt. Hierbei zeigt sich eine gute baupraktische Übereinstimmung zwischen komplexen Berechnungen und dem vereinfachten Berechnungsansatz. Deformation Forecast of Prestressed and Non-Prestressed Concrete Members Comparative investigations have shown that the limitation of deformation, based on a permitted slenderness ratio as possible according to DIN 1045-1 for reinforced concrete elements, do not always achieve the desired success. An exact calculation of the structure deformation is absolutely necessary for prestressed components and in the case of a non-accomplished slenderness proof for reinforced concrete members. In this paper significant material influences of the deformation forecast will be discussed, proceeding from universal views of the component deformation proof. It will be clear, that an exact deformation calculation is only restricted possible. An approximation procedure for practical use to the forecast of deformations of reinforced and prestressed concrete structures will be formulated, afterwards. The accuracy of this developed approximation procedure will be estimated with the aid of comparative studies. At this, the results of the simplified formulation correlate well with the values of complex, numeric investigations in a range of practical use. [source]

Buchbesprechung: fib Bulletin 38: Fire design of concrete structures , materials, structures and modelling

BETON- UND STAHLBETONBAU, Issue 9 2007
Frank Fingerloos
No abstract is available for this article. [source]

Kombiniertes Verfahren zur wirklichkeitsnahen Berechnung schlanker Stahlbetonstabtragwerke

BETON- UND STAHLBETONBAU, Issue 10 2006
Uwe Starossek Univ.-Prof.
Der wirklichkeitsnahen und damit nichtlinearen Berechnung von allgemeinen Stahlbetontragwerken kommt eine wachsende Bedeutung zu. Eine Kombination des allgemeinen Weggrößenverfahrens, des Übertragungsverfahrens und eines Querschnittsmoduls führt zu einem effektiven Berechnungsverfahren für allgemeine Stabtragwerke aus Stahl- und Spannbeton. Neben der stofflichen Nichtlinearität berücksichtigt das Verfahren auch geometrische Nichtlinearität mit großen Verformungen. Die übergeordnete Berechnung des Systems erfolgt inkrementell und iterativ mit dem allgemeinen Weggrößenverfahren. Auf Stabebene wird ein erweitertes Übertragungsverfahren zur Bestimmung der Stabendschnittgrößen und der Steifigkeitsmatrix eingesetzt. Die Formulierung des Übertragungsverfahrens erfolgt in einem rekursiven Schema für einen verformten Stab, der in Abhängigkeit vom Steifigkeitsgradienten in einzelne Abschnitte diskretisiert wird. Das nichtlineare Materialverhalten einschließlich Rißbildung, Entfestigung und Fließen der Bewehrung wird im Querschnittsmodul über eine Querschnittsintegration erfaßt. Combined method for a realistic analysis of slender reinforced concrete frames A more realistic and, hence, nonlinear analysis of reinforced concrete structures is becoming increasingly important. A combination of the displacement method, the transfer matrix method, and a cross section module is suggested which leads to an effective analysis method for general reinforced and prestressed concrete frames. The combined method considers both material and geometrical nonlinearities including large deformations. The first level computation of the system is incrementally and iteratively carried out by the displacement method. At element level, an extended transfer matrix method is used for determining both the internal forces at the element end nodes and the stiffness matrix. The transfer matrix method is recursively applied to the deformed element, which is discretized into individual segments whose number and lengths depend on the stiffness gradient. The cross section module is based on cross-sectional integration. It takes into account nonlinear material behavior including cracking, softening, and yielding of reinforcement. [source]

Schutz und Instandsetzung von Betonbauteilen mit genormten Produkten nach EN 1504

BETON- UND STAHLBETONBAU, Issue 10 2006
M. Raupach Prof. Dr.-Ing.
Die Europäische Normenreihe EN 1504 für Schutz und Instandsetzung von Betonbauteilen steht unmittelbar vor ihrer Fertigstellung. Sie besteht aus 10 Hauptnormen und 62 zugehörigen Europäischen Prüfnormen. Die Hauptnormen EN 1504-2 bis 7 regeln die Produktgruppen Oberflächenschutzsysteme, Mörtel, Klebstoffe für Verstärkungen, Riß- und Hohlraumfüllstoffe, Ankermörtel sowie die Stahlbeschichtungen. Die Prinzipien für den Gebrauch der Produkte sowie die Anwendung der Produkte auf der Baustelle mit zugehöriger Qualitätssicherung sind in den Teilen 9 und 10 enthalten. Ferner ist die Qualitätssicherung der Produkte in Teil 8 geregelt. Somit liegt in Kürze ein umfassendes Normenwerk für Schutz und Instandsetzung von Betonbauteilen vor. Derzeit wird beraten, wie dieses Normenwerk in Deutschland eingeführt wird. Aus verschiedenen Gründen wurde beschlossen, daß die Teile für Planung und Anwendung in Deutschland nicht eingeführt werden, weil mit den bestehenden Richtlinien des DAfStb "Schutz und Instandsetzung von Betonbauwerken" sowie der ZTV-ING langjährig bewehrte Regelwerke vorliegen. Um die Europäisch zukünftig mit CE-Zeichen markierten Produkte für Schutz und Instandsetzung von Betonbauwerken verwenden zu können, wurden für den Oberflächenschutz, die Mörtel, Rißfüllstoffe und die Stahlbeschichtungen inzwischen entsprechende Restnormen (DIN V 18026 bis 18028) erarbeitet, während die Kleber und Ankermörtel wie bisher in Zulassungen geregelt werden. In diesem Beitrag wird beschrieben wie zukünftig in Deutschland Schutz und Instandsetzung von Betonbauteilen mit genormten Produkten nach EN 1504 erfolgen soll. Repair and protection of concrete structures using products according to the standard EN 1504 The European series of standards EN 1504 for protection and repair of concrete structures is actually more or less finished. It consists of 10 main standards and 62 European test standards. The main standards EN 1504-2 to 7 refer to the product classes surface protection systems, mortars, adhesives for strengthening, materials for filling of cracks and voids, anchoring products as well as protection materials for the steel surface. The principles for the use of the products and systems as well as the application of the products on site including quality assurance are regulated in parts 9 and 10. Furthermore the quality assurance for the products is described in part 8. In this way within the next months an extensive set of standards for protection and repair of concrete structures is available. Actually it is discussed, how this set of standards will be introduced in Germany. Due to different reasons it has been decided, that the parts for design and application will not be introduced in Germany, because the existing standards of the DAfStb "Protection and repair of concrete structures" as well as the ZTV-ING have been used successfully for several years. To be able to use the European CE-marked products for protection and repair of concrete structures in future in Germany, for surface protection, mortars, materials for filling of cracks and voids as well as steel coatings in the meantime additional standards (DIN V 18026 to 18028) have been worked out, while the adhesives and anchoring products will be handled via approvals as before. This paper describes, how protection and repair of concrete structures will be carried out in Germany with CE-marked products according to EN 1504. [source]

Die neue Anwendungsnorm DIN V 18197 "Abdichten von Fugen in Beton mit Fugenbändern": Fugenbänder fachgerecht geplant, ausgewählt und eingebaut

BETON- UND STAHLBETONBAU, Issue 11 2005
Rainer Hohmann Prof. Dr.-Ing.
Fugenbänder werden seit Jahrzehnten erfolgreich zur Abdichtung von Bewegungs- und Arbeitsfugen in wasserundurchlässigen Bauwerken aus Beton eingesetzt. Mit der DIN V 18197 "Abdichten von Fugen in Beton mit Fugenbändern" wird nun sowohl dem Planer als auch dem Ausführenden ein Regelwerk zur Verfügung gestellt, in dem neben relevanten Hinweisen für die Planung und eine fachgerechte Handhabung von Fugenbändern auf der Baustelle auch Auswahldiagramme zu finden sind, mit denen der Planer in Abhängigkeit von der Beanspruchung auf einfache Art Fugenbänder auswählen kann. Dieser Beitrag geht auf die wesentlichen die Fugenabdichtung mit Fugenbändern betreffenden Regeln ein und zeigt an ausgewählten Beispielen, wie der Planer das auf seine Belastungen abgestimmte Fugenband mit Hilfe der Auswahldiagramme der DIN V 18197 auswählen kann. The new German Standard DIN V 18197 "Sealing of joints in concrete with waterstops" , waterstops correctly designed, dimensioned and used For decades, waterstops are successfully used for the waterproofing of movement and construction joints in watertight concrete structures. The DIN V 18197 "Sealing of joints in concrete with waterstops", provides a set of rules for both, the planner and the contractor. In addition to relevant details for the design and the professional handling of waterstops on the construction site, selection diagrams are included which, in a simple way, allows the planner to select waterstops in dependence of the loads. This article addresses to the essential rules concerning the joint waterproofing with waterstop and explains by means of several examples and the DIN V 18197 selection diagrams, how the planner can specify a waterstop complying with the loads. [source]