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Reinforcing Steel (reinforcing + steel)

Distribution by Scientific Domains

Engineering	80%

Selected Abstracts

Versuche zur Ermüdungsfestigkeit alter Betonstähle

BETON- UND STAHLBETONBAU, Issue 7 2009
Patrick Fehlmann Dipl.
Baustoffe; Bewehrung; Versuche; Brückenbau Abstract Die Frage der Ermüdungssicherheit hat im Zusammenhang mit der Überprüfung bestehender Stahlbetonbauwerke, insbesondere Brücken, an Aktualität gewonnen. Während auf der Einwirkungsseite die Anzahl der Lastwechsel und die Lasten, die die Brücke im Laufe ihres Lebens erfahren hat, von Bedeutung sind, sind es auf der Widerstandsseite die Genauigkeit des Tragwerkmodells und die Materialkennwerte. Mit Letzteren befasst sich dieser Aufsatz. Der wichtigste Parameter auf der Widerstandsseite ist die Ermüdungsfestigkeit des Betonstahls. Mittels Dauerschwingversuchen wurde die Ermüdungsfestigkeit von vier Betonstahlsorten ermittelt. Zwei Sorten stammen von abgebrochenen Brücken aus den 1950er Jahren; zwei weitere sind kürzlich produzierte Sorten von Ring- und Stabmaterial der Betonstahlsorte B 500 B. Das Ziel der Versuche bestand darin, festzustellen, ob das Alter einer Stahlbetonkonstruktion einen Einfluss auf die Ermüdungsfestigkeit des Betonstahls hat. Im Aufsatz werden die Problematik beim Nachweis der Ermüdungssicherheit bestehender Brücken kurz geschildert, die Versuche beschrieben und deren Resultate diskutiert. Fatigue Tests with Old Reinforcing Steels Recently, fatigue safety has become an issue with respect to surveying the condition of existing structures, in particular bridges. While questions considering traffic loads and frequencies dominate the calculations of the appropriate load scenarios, the accuracy of the structural model and material properties play a vital role for the calculation of the resistance. This article deals with the latter. The most important parameter on the resistance side is the fatigue strength of the reinforcement. Therefore, fatigue strength of four brands of reinforcing steel was determined in fatigue tests. Two brands of reinforcement bars could be gathered during demolition work of two bridges which were built in the 1950ies. Another two brands of new reinforcing steel B 500 B, a rod-steel and a steel from the roll, were tested. The aim of the tests was to prove whether age and environment of the built-in reinforcement bars affect their fatigue resistance or not. The article briefly describes the difficulties with verifying the fatigue safety of existing bridges while the main part deals with the experimental work and the discussion of the test results. [source]

Numerical Model for Biaxial Earthquake Response of Reinforced Concrete

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2007
Cemalettin Dönmez
The model is tested using data from two types of experiments with reinforced concrete elements: (1) elements subjected to varying pseudo-static biaxial lateral loads and (2) elements that responded biaxially to simulated earthquake motions. The goal for the model was not only to help determine the absolute maxima for earthquake response but also to enable calculation of the entire waveform, including the ranges of low- and moderate-amplitude response. The comparisons of measured and calculated results and sensitivity of the proposed model to variations in the input parameters are discussed. The output was found to be insensitive to the changes in input parameters related to concrete and sensitive to input parameters related to reinforcing steel. The results of the calculations were tested using experimental data. [source]

Prediction of Onset of Corrosion in Concrete Bridge Decks Using Neural Networks and Case-Based Reasoning

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2005
G. Morcous
It is based on the integration of artificial neural network (ANN), case-based reasoning (CBR), mechanistic model, and Monte Carlo simulation (MCS). A probabilistic mechanistic model is used to generate the distribution of the time to corrosion initiation based on statistical models of the governing parameters obtained from field data. The proposed ANN and CBR models act as universal functional mapping tools to approximate the relationship between the input and output of the mechanistic model. These tools are integrated with the MCS technique to generate the distribution of the corrosion initiation time using the distributions of the governing parameters. The proposed methodology is applied to predict the time to corrosion initiation of the top reinforcing steel in the concrete deck of the Dickson Bridge in Montreal. This study demonstrates the feasibility, adequate reliability, and computational efficiency of the proposed integrated ANN-MCS and CBR-MCS approaches for preliminary project-level and also network-level analyses. [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]

Zur Momentenumlagerung in Elementdecken mit Gitterträgern

BETON- UND STAHLBETONBAU, Issue 12 2006
Rüdiger Beutel Dr.-Ing.
Elementdecken aus vorgefertigten Stahlbetonplatten mit Gitterträgern und aufbetonierter Ortbetonschicht werden bei einem zusätzlichen Nachweis der Verbundfuge wie Ortbetondecken bemessen. Während nichtlineare und plastische Bemessungsverfahren in bauaufsichtlichen Zulassungen für Gitterträger derzeit aufgrund mangelnder Erfahrung ausgeschlossen sind, ist eine lineare Schnittgrößenermittlung mit nachträglicher begrenzter Momentenumlagerung wie bei Ortbetondecken möglich. Für Momentenumlagerungen von 30% muß nach DIN 1045-1 hochduktiler Betonstahl für die Biegezugbewehrung verwendet werden. Wenngleich DIN 1045-1 hierbei normalduktilen Betonstahl für Gitterträger nicht ausschließt, ist die notwendige Rotationsfähigkeit sicherzustellen. Vier Versuche am Institut für Massivbau der RWTH Aachen haben gezeigt, daß auch mit Gitterträgern aus normalduktilem Betonstahl große plastische Rotationen möglich sind, ohne daß eine Reduktion der Querkrafttragfähigkeit festzustellen war. Moment Redistribution in Precast Plates with Lattice Girders Semi precast slabs consist of precast plates with lattice girders and an in-situ concrete topping. The structural behaviour is nearly equivalent to monolithic slabs. However, the shear capacity at the interface between precast element and concrete topping has to design thoroughly. Although technical approvals of lattice girders do not allow non-linear analysis due to insufficient experience, a linear elastic analysis with limited moment redistribution is permitted. For a moment redistribution of 30% the use of class B (high ductility) reinforcement is required according to DIN 1045-1. Hereby, a sufficient rotation capacity has to be ensured for both bending reinforcement and lattice girder, too. Beam tests with lattice girders of class A (normal ductility) reinforcing steel have performed at the institute of structural concrete at RWTH Aachen University revealed high plastic rotations without reducing the shear capacity. [source]