Home About us Contact
|
Home About us Contact | ||
|
|
||
Concrete Slabs (concrete + slab)
Selected AbstractsCoupled damage and plasticity modelling in transient dynamic analysis of concreteINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 1 2002Fabrice 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] A new triangular layered plate element for the non-linear analysis of reinforced concrete slabsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2006Y. X. Zhang Abstract A new 3-node, 18-DOF triangular layered plate element is developed in this paper for the geometric and material non-linear analysis of isotropic plates and reinforced concrete slabs under service loads. The proposed model is a combination of Allman's 3-node, 9-DOF triangular membrane element with drilling degrees of freedom and the refined non-conforming 3-node, 9-DOF triangular plate-bending element RT9 in order to account for the coupling effects between membrane and bending actions. The element is modelled as a layered system of concrete and equivalent smeared steel reinforcement layers, and perfect bond is assumed between the concrete layers and the smeared steel layers. The maximum normal stress criterion is employed to detect cracking of the concrete, and a smeared fixed crack model is assumed. Both geometric non-linearity with large displacements but moderate rotations and material non-linearity, which incorporates tension, compression, concrete cracking and tension stiffening, are included in the model. An updated Lagrangian approach is employed as a solution strategy for the non-linear finite element analysis and a numerical example of reinforced concrete slab is given to demonstrate the efficacy of this robust element. Copyright © 2005 John Wiley & Sons, Ltd. [source] Innovative Betone für Holz-Beton-VerbundkonstruktionenBAUTECHNIK, Issue 11 2004Klaus Holschemacher Prof. Dr.-Ing. Die Holz-Beton-Verbundbauweise kommt gegenwärtig vor allem in Form von Deckenkonstruktionen, entweder bei Neubauvorhaben oder im Rahmen der Verstärkung von vorhandenen Holzbalkendecken, zur Anwendung. Das Tragverhalten der Holz-Beton-Verbunddecken wird durch die Materialeigenschaften der Betonplatte und der Holzbalken sowie die Effizienz des Verbundes zwischen diesen beiden Querschnittsteilen bestimmt. Da der Baupraxis mittlerweile ein großes Spektrum unterschiedlicher innovativer Betone für die verschiedensten Anwendungsmöglichkeiten zur Verfügung steht, ist es notwendig zu prüfen, welche dieser Betone für den Einsatz in Holz-Beton-Verbundkonstruktionen besonders geeignet sind. Im einzelnen wird auf selbstverdichtenden Beton, Stahlfaserbeton, konstruktiven Leichtbeton sowie hochfesten und ultrahochfesten Beton eingegangen und deren Vor- bzw. Nachteile unter Berücksichtigung statisch-konstruktiver Aspekte, wirtschaftlicher und bauphysikalischer Gesichtspunkte sowie Fragen der Bauausführung bewertet. Innovative concretes for timber-concrete composite constructions. Timber-concrete composite constructions are currently applied mainly for new buildings or when strengthening existing timber beam slabs. The load bearing capacity of timber-concrete composite slabs is essentially affected by the material properties of the concrete slab and timber beam itself as well as the efficiency of bond between both parts. As nowadays a wide spectrum of different innovative concretes is available their applicability for timber-concrete composite constructions has to be verified. In the following the focus is set for self-consolidating concrete, steel fibre reinforced concrete, structural lightweight concrete, high-strength and ultra high-strength concrete. The advantages but also disadvantages of these concretes will be explained considering structural, economic and processing aspects and building physics. [source] Anwendung von Trapezblechstegen im BrückenbauBETON- UND STAHLBETONBAU, Issue 9 2009Längsschubtragverhalten von Betondübeln in Kombination mit Trapezblechstegen Brückenbau; Entwurf und Konstruktion Abstract Trapezblechstege im Brückenbau kommen trotz der großen Vorteile, die diese Bauweise bietet, in Deutschland bisher nur an einem Pilotprojekt zur Anwendung. Durch die charakteristischen Eigenschaften des Trapezbleches entstehen konstruktive und wirtschaftliche Vorteile gegenüber herkömmlichen Brückenbauweisen. Allerdings lassen die aktuell gültigen Regelwerke aufgrund fehlender Kenntnis zum Tragverhalten und mangelnder Erfahrung keine wirtschaftliche Ausbildung zu. Dies zeigt sich am Beispiel des Pilotprojekts. Die Ausbildung der Verbundfuge wurde hier nur sehr unbefriedigend gelöst und verdeutlicht somit die Notwendigkeit einfacher und praktikabler Verbindungsmöglichkeiten. Am Institut für Leichtbau Entwerfen und Konstruieren der Universität Stuttgart wurde in Zusammenarbeit mit dem Institut für Konstruktion und Entwurf ein von der Forschungsvereinigung für Stahlanwendung e. V. (FOSTA) finanziertes Forschungsvorhaben bearbeitet, bei dem unterschiedliche Verbundfugenausbildungen numerisch und experimentell untersucht wurden. Der folgende Beitrag beschränkt sich auf die Verwendung von Betondübeln als Verbundmittel und stellt hierfür ein einfaches Bemessungskonzept für die Verbundsicherung unter Längsschubbeanspruchung im Grenzzustand der Tragfähigkeit vor. The use of corrugated steel webs in bridge constructions , Load bearing behaviour of concrete dowels in combination with corrugated steel webs under longitudinal shear Studies of the load bearing behaviour under shear force of integrated connections at composite bridge girders using corrugated steel webs. Up to now there is only one project in Germany, where the application of corrugated steel webs has been practiced in the field of composite bridges. Due to the characteristics of the corrugated steel web this construction method has constructive and economic advantages. However there is a lack of experiences and standards to fully utilize these advantages and to allow an economic application. Especially the first project in Germany expose some critical points. The design of the joint between the concrete slab and the corrugated steel web is actually not satisfactory and shows the need for simpler and more practicable connection methods. At the Institute for Lightweight Structures and Conceptual Design at Universität Stuttgart and together with the Institute of Structural Design, a research project, financed by Forschungsvereinigung für Stahlanwendung e. V. (FOSTA) was made. Within this project different types of composite joints were experimentally and numerically analysed. This paper deals only with the investigations of concrete dowels as connectors. On the basis of these studies simple design rules for shear connection in the ultimate limit state were developed. [source] Ductility of Reinforced Concrete Flat Slab-Column ConnectionsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2005Maria Anna Polak Post peak-load ductility of connections in reinforced concrete framed structures is essential for ensuring structural integrity and preventing local failure that may lead to progressive collapse of such systems. The importance of ductility for resistance against abnormal loading and the role of transverse reinforcement in providing ductility is discussed, and a new shear-strengthening technique, shear bolts, is presented. Shear bolts are a special type of reinforcement developed specially for retrofitting of existing, previously built, flat slabs. The results of an experimental work are presented which show how transverse reinforcement increases punching shear capacity and post-failure ductility of slab-column connections. The described work also applies a specially developed finite element formulation based on layered shell elements, to the analysis of continuous reinforced concrete slabs. The formulation is applicable for global structural analysis of slabs failing in flexure or punching modes. The finite element and experimental results are compared in the article. [source] Seismic performance evaluation of a 34-story steel building retrofitted with response modification elementsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2009Yuan-Tao Weng Abstract The original structural design of this case study consisted of five basement floors and a 34-story hotel tower in Kaohsiung, Taiwan. The construction started in 1993, and the erection of the entire steel frame and the pouring of concrete slabs up to the 26th floor were completed before 1996. However, construction of the original hotel was subsequently suspended for 10 years. Recently, this building has been retrofitted for residential purposes. Buckling restrained braces (BRBs) and eccentrically braced frames were incorporated into the seismic design of the new residential tower. This paper presents the seismic resisting structural system, seismic design criteria, full-scale test results of one BRB member and the as-built welded moment connections. Test results confirm that the two side web-plate stiffening details can effectively improve the rotational capacity of welded moment connection. The paper also discusses the analytical models for simulating the experimental responses of the BRB members and the welded moment connections. Nonlinear response history analyses (NLRHA) indicate that the inelastic deformational demands of the original and the redesigned structures induced by the maximum considered earthquakes are less than those found in the seismic building codes or laboratory tests. This paper also proposes a ground motion scaling method considering multi-mode effects for NLRHA of the example building. It is shown that the proposed scaling method worked well in reducing the scatter in estimated peak seismic demands. Copyright © 2008 John Wiley & Sons, Ltd. [source] A new triangular layered plate element for the non-linear analysis of reinforced concrete slabsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2006Y. X. Zhang Abstract A new 3-node, 18-DOF triangular layered plate element is developed in this paper for the geometric and material non-linear analysis of isotropic plates and reinforced concrete slabs under service loads. The proposed model is a combination of Allman's 3-node, 9-DOF triangular membrane element with drilling degrees of freedom and the refined non-conforming 3-node, 9-DOF triangular plate-bending element RT9 in order to account for the coupling effects between membrane and bending actions. The element is modelled as a layered system of concrete and equivalent smeared steel reinforcement layers, and perfect bond is assumed between the concrete layers and the smeared steel layers. The maximum normal stress criterion is employed to detect cracking of the concrete, and a smeared fixed crack model is assumed. Both geometric non-linearity with large displacements but moderate rotations and material non-linearity, which incorporates tension, compression, concrete cracking and tension stiffening, are included in the model. An updated Lagrangian approach is employed as a solution strategy for the non-linear finite element analysis and a numerical example of reinforced concrete slab is given to demonstrate the efficacy of this robust element. Copyright © 2005 John Wiley & Sons, Ltd. [source] Simulation of high velocity concrete fragmentation using SPH/MLSPHINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2003T. Rabczuk Abstract The simulation of concrete fragmentation under explosive loading by a meshfree Lagrangian method, the smooth particle hydrodynamics method (SPH) is described. Two improvements regarding the completeness of the SPH-method are examined, first a normalization developed by Johnson and Beissel (NSPH) and second a moving least square (MLS) approach as modified by Scheffer (MLSPH). The SPH-Code is implemented in FORTRAN 90 and parallelized with MPI. A macroscopic constitutive law with isotropic damage for fracture and fragmentation for concrete is implemented in the SPH-Code. It is shown that the SPH-method is able to simulate the fracture and fragmentation of concrete slabs under contact detonation. The numerical results from the different SPH-methods are compared with the data from tests. The good agreement between calculation and experiment suggests that the SPH-program can predict the correct maximum pressure as well as the damage of the concrete slabs. Finally the fragment distributions of the tests and the numerical calculations are compared. Copyright © 2003 John Wiley & Sons, Ltd. [source] A field study of critical chloride content in reinforced concrete with blended binderMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2009L. Tang Abstract This paper presents the results from the investigation of chloride-induced reinforcement corrosion in concrete slabs after over 13 years exposure in the marine environment. In the beginning of 1990s over 40 reinforced concrete slabs with different types of binder and water/binder ratios were exposed in a marine environment at Swedish west coast. In this study a new rapid technique was used for non-destructive measurement of corrosion. Based on the results from the non-destructive measurement, the actual corrosion of steel bars in five concrete slabs was visually examined and the chloride profiles in the penetrating direction as well as at the cover level were measured. The results show that the visible corrosion normally occurred about 10,20 cm under the seawater level, where the oxygen may be sufficiently available for initiating the corrosion. It is also found that chloride may easily penetrate through a poor interface between concrete and mortar spacer and initiate an early corrosion. As a conclusion, although the chloride level 1% by mass of binder may not be the same as the conventionally defined threshold value, it can be taken as the critical level for significant on-going corrosion that is visible by destructive visual examination, despite types of binder. [source] Durchstanzversuche mit Bewehrung mit hochfestem Verbund, innovative Traganalysen und BemessungsansätzeBETON- UND STAHLBETONBAU, Issue 8 2007Richard Rojek Prof. Dr.-Ing. Im vorliegenden Aufsatz wird über Durchstanzversuche berichtet, bei denen in die Stahlbeton-Versuchsplatten als Durchstanzsicherung Bewehrung mit hochfestem Verbund eingebaut wurde. Die Versuchsergebnisse zeigen, dass mit diesem System sehr gute Tragfähigkeiten erreicht werden. Aus den Rissbildern der nach den Versuchen aufgeschnittenen Versuchsplatten konnten interessante Rückschlüsse auf die Tragwirkung des Systems gezogen werden. Ein Vergleich dieser Rissbilder mit denjenigen von Versuchsplatten mit Doppelkopfankern als Durchstanzsicherung zeigt im Detail deutliche Unterschiede im Tragverhalten. Die Analyse der Versuchsergebnisse führt außerdem zu neuartigen Erkenntnissen über die Tragmechanismen im durchstanzgefährdeten Auflagerbereich von Stahlbetonplatten, die auch die Grundlage für einen Vorschlag bieten, die bestehenden Bemessungsregeln zu modifizieren. Slab Punching Tests with Reinforcement with High-Strength Bond In this paper there is given an account of punching tests, in which the tested concrete slabs were reinforced against punching by reinforcement with high-strength bond. The test results show that very good load capacities are obtainable. The pictures of the cracks, which were to be seen after the test slabs were cut up, gave interesting conclusions about the carrying behaviour of the system. Comparing these cracks with those of test slabs with double headed punching anchors clearly shows the differences of the carrying behaviours. The analysis of the test results also gives new knowledge about the carrying mechanisms at the critical punching zone of reinforced concrete slabs, which also build a basis for a proposal how to modify the existing design rules. [source] Größere Spannweiten durch Flachdecken aus Konstruktions-LeichtbetonBETON- UND STAHLBETONBAU, Issue 5 2006Julia Stracke Dr.-Ing. Konstruktions-Leichtbeton weist im Vergleich zu Normalbeton ein deutlich günstigeres Verhältnis von Eigengewicht zu Festigkeit auf. Es werden die hieraus resultierenden Möglichkeiten zur Optimierung von Flachdecken gerade im Hinblick auf größere Spannweiten aufgezeigt. Unter Berücksichtigung der baustoffspezifischen Eigenschaften des Leichtbetons und deren Auswirkungen auf das Tragsystem einer Flachdecke wird die Lösung einer Hohlkörperdecke entwickelt, bei der Leicht- und Normalbeton kombiniert eingesetzt werden. Damit können deutlich größere Spannweiten erreicht werden als mit herkömmlichen, nicht vorgespannten Normalbetondecken. Wide spans due to Flat Slabs with Structural lightweight aggregate Concrete Structural lightweight aggregate concrete (SLWAC) shows a much more favourable ration of dead weight to strength than normal weight concrete. The present report indicates the possibilities resulting out of this for the optimisation of flat slabs in view of wider spans. Considering the specific material properties of SLWAC and their consequences on the load bearing system of flat slabs the solution of a hollow body slab is developed in which SLWAC and normal weight concrete are used combined. Those slab systems reach clearly wider spans than conventional nonprestressed normal weight concrete slabs. [source] Einfluß der Elementfugen auf die Durchbiegung von FlachdeckenBETON- UND STAHLBETONBAU, Issue 3 2006Manfred Curbach Prof. Dr.-Ing. Das Verformungsverhalten von Flachdecken in Elementbauweise unterscheidet sich von einer reinen Ortbetondecke aufgrund der vorhandenen Elementfugen. Die damit verbundenen lokalen Querschnittsschwächungen erfordern schon auf niedrigem Lastniveau eine Umlagerung der Belastung in angrenzende Feld- und Stützbereiche. Die Folge der Lastumlagerung sind anfänglich höher beanspruchte Deckenbereiche und eine frühere Rißbildung im Vergleich zu einer reinen Ortbetondecke. Mit steigender Belastung kommt es jedoch zur Annäherung der Rißzustände von Fertigteil- und Ortbetondecken, wie anhand nichtlinearer Berechnungen nachgewiesen werden konnte. Der relative Unterschied in der Durchbiegung wird deutlich reduziert. Auf Gebrauchslastniveau liegen die Verformungen der Fertigteildecken etwa 5% über denen der reinen Ortbetondecke. Influence of Bond Joints on Deformation of precast Slabs Precast slabs and in-situ concrete slabs vary in their deflection behaviour due to the bond joints between the precast concrete units. The diminished cross section of the bond joints require a redistribution of internal forces to adjoining field and support areas already at a small load. The consequence of this redistribution are higher demands in these slab areas and an earlier crack initiation in comparison to the in-situ concrete slabs. With an increase of the loading the cracking pattern of the precast slabs and the in-situ concrete slabs converge as the nonlinear FE-calculation have shown. The relative difference in deformation is clearly reduced. At the service load the deformation of the precast slabs is only 5% higher than the deformation of the in-situ concrete slabs. [source] | ||||||||||||||||||||||