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Experimental and numerical studies of mono-strand anchorage
Marceau, D.,Bastien, J.,Fafard, M.,Chabert, A. Techno-Press 2001 Structural Engineering and Mechanics, An Int'l Jou Vol.12 No.2
This paper deals with an experimental and numerical study of a mono-strand wedge anchor head mechanism. First, the experimental program is presented and monitored data such as wedge slippage, anchor deflection and strain distributions along external peripheral surfaces of the anchor head are presented and discussed. In accordance with the experimental set up, these data concern only the global behaviour of the mechanism and cannot provide valuable information such as internal stress-strains distributions, stress concentrations and percentage of yielded volume. Therefore, the second part of this paper deals with the development of an efficient numerical finite element model capable of providing mechanism of the core information. The numerical model which includes all kinematics/material/contact non-linearities is first calibrated using experimental data. Subsequently, a numerical study of the anchorage mechanism is performed and its behaviour is compared to the behaviour of a slightly geometrically modified mechanism where the external diameter has been increased by 5 mm. Finally, different topics influencing the anchorage mechanism behaviour are addressed such as lubrication and wedge shape.
Marceau, D.,Fafard, M.,Bastien, J. Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.15 No.6
Mechanical anchorage devices are generally tested in the laboratory and may be analyzed using the finite element method. These devices are composed of many components interacting through diverse contact interfaces. Generally, a Coulomb friction law is sufficient to take into account friction between smooth surfaces. However, in the case of mechanical anchorages, a gripping system, named herein the wedge-tendon system, is used to anchor the prestressing tendon. The wedge inner surface is made of a series of triangular notches designed to grip the tendon. In this particular case, the Coulomb law is not adapted to simulate the contact interface. The present paper deals with a new constitutive contact/gripping law to simulate the gripping effect. A parameter identification procedure, based on experimental results as well as on a finite element/neural network approach, is presented. It is demonstrated that all parameters have been selected in a satisfactory way and that the proposed constitutive law is well adapted to simulate the wedge gripping effect taking place in a mechanical anchorage device.
Numerical study of mono-strand anchorage mechanism under service load
Marceau, D.,Fafard, M.,Bastien, J. Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.18 No.4
Anchorage devices play an important role in post-tensioned bridge structures since they must sustain heavy loads in order to permit the transfer of the prestressing force to the structure. In external prestressing, the situation is even more critical since the anchorage mechanisms, with the deviators, are the only links between the structure and the tendons throughout the service life of the structure. The behaviour of anchorage devise may be studied by using the finite element method. To do so, each component of the anchorage must be adequately represented in order to approximate the anchor mechanism as accurately as possible. In particular, the modelling of the jaw/tendon device may be carried out using the real geometry of these two components with an appropriate constitutive contact law or by replacing these components by a single equivalent. This paper presents the numerical study of a mono-strand anchorage device. The results of a comparison between two different representations of the jaw/tendon device, either as two distinct components or as a single equivalent, will be examined. In the double-component setup, the influence of the wedge configuration composing the jaw, and the influence of lubrication of the anchor, will be assessed.
Yao, M.J.,Dey, P.,Seol, J.B.,Choi, P.,Herbig, M.,Marceau, R.K.W.,Hickel, T.,Neugebauer, J.,Raabe, D. Elsevier Science 2016 Acta materialia Vol.106 No.-
<P>We report on the investigation of the off-stoichiometry and site-occupancy of kappa-carbide precipitates within an austenitic (gamma), Fe-29.8Mn-7.7Al-1.3C (wt.%) alloy using a combination of atom probe tomography and density functional theory. The chemical composition of the kappa-carbides as measured by atom probe tomography indicates depletion of both interstitial C and substitutional Al, in comparison to the ideal stoichiometric L'12 bulk perovskite. In this work we demonstrate that both these effects are coupled. The off-stoichiometric concentration of Al can, to a certain extent, be explained by strain caused by the kappa/gamma mismatch, which facilitates occupation of Al sites in kappa-carbide by Mn atoms (Mn-Al(gamma) anti-site defects). The large anti-site concentrations observed by our experiments, however, can only be stabilized if there are C vacancies in the vicinity of the anti-site. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.</P>