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Arias L.,IRSTEA | Bertrand-Krajewski J.-L.,CNRS Laboratory of Civil and Environmental Engineering | Molle P.,IRSTEA
Water Science and Technology

Designing vertical-flow constructed wetlands (VFCWs) to treat both rain events and dry weather flow is a complex task due to the stochastic nature of rain events. Dynamic models can help to improve design, but they usually prove difficult to handle for designers. This study focuses on the development of a simplified hydraulic model of French VFCWs using an empirical infiltration coefficient - infiltration capacity parameter (ICP). The model was fitted using 60-second-step data collected on two experimental French VFCW systems and compared with Hydrus 1D software. The model revealed a season-by-season evolution of the ICP that could be explained by the mechanical role of reeds. This simplified model makes it possible to define time-course shifts in ponding time and outlet flows. As ponding time hinders oxygen renewal, thus impacting nitrification and organic matter degradation, ponding time limits can be used to fix a reliable design when treating both dry and rain events. © IWA Publishing 2014. Source

Xu H.,Hong Kong Polytechnic University | Su Z.,Hong Kong Polytechnic University | Cheng L.,Hong Kong Polytechnic University | Guyader J.-L.,INSA Lyon | Hamelin P.,CNRS Laboratory of Civil and Environmental Engineering
Structural Health Monitoring

Interfacial debonding in multilayered engineering structures can jeopardize the structural integrity without timely awareness. By reconstructing the distribution of interfacial forces and canvassing local perturbance to the structural dynamic equilibrium, an identification approach for interfacial debonding between different structural components was developed. A "debonding index," governed by the derivatives of reconstructed interfacial forces, was established, able to predict debonding in a quantitative manner including the coexistence of multi-debonding and their individual locations and sizes. The index offers the flexibility of detecting debonding between a beam-like component and its neighboring constituents of any type (beam, plate, shell, or even more complex components) with distinct material properties. To enhance the robustness of the approach under noisy measurement conditions, two denoising techniques (low-pass wavenumber filtering and adjustment of measurement density), together with a data fusion algorithm, were proposed. Using a noncontact laser vibrometry, the approach was validated experimentally by identifying multiple debonding zones in a steel-reinforced concrete slab dismantled from a bridge model. The approach has been demonstrated sensitive to debonding of small dimension owing to the use of high-order differential equation of motion. In addition, it does not require a global model of the entire system, prior information on structural boundaries, benchmark, baseline signals, and additional excitation sources as long as the structure undergoes steady vibration. © The Author(s) 2013. Source

Plante B.,University of Quebec | Bussiere B.,University of Quebec | Benzaazoua M.,University of Quebec | Benzaazoua M.,CNRS Laboratory of Civil and Environmental Engineering
Journal of Geochemical Exploration

It is crucial for mining operators to predict the acid-generating potential of their mine wastes as early as possible in a mine development project, because of the high remediation costs of acid-generating tailings and the risks of environmental issues associated with an incorrect classification of the wastes. However, many tailings having low net acid-generating potentials fall into the uncertainty zone of the static test. Different chemical and mineralogical static test results are compared in this paper for 5 Canadian hard rock mine tailings having low net acid-generating potential, in order to help determine which method is more appropriate for such tailings. Static test methods showed significant result variations (NNP or NP/AP) for each tailings tested, demonstrating the need to develop tools to identify the most appropriate technique for a given mine waste. Thus, static test selection guidelines were developed based on mineralogical considerations for each test. A modification to the Lawrence and Scheske method based on the Paktunc CNP method is proposed in order to improve its accuracy, which enables to account for the presence of oxidizable cations (such as iron and manganese) within the minerals. © 2011 Elsevier B.V. Source

Brun M.,CNRS Laboratory of Civil and Environmental Engineering | Batti A.,CNRS Contacts and Structural Mechanics Laboratory | Combescure A.,CNRS Contacts and Structural Mechanics Laboratory | Gravouil A.,CNRS Contacts and Structural Mechanics Laboratory | Gravouil A.,Institut Universitaire de France
Finite Elements in Analysis and Design

External coupling software based on the coupling algorithm proposed by Prakash and Hjelmstad (PH method) is compared to the previous external coupling software based on the GC (Gravouil and Combsecure) method. The salient features of multi-time-step partitioning methods are presented: they involve non-overlapping partitions and follow a dual Schur approach by enforcing the velocity continuity at the interface with Lagrange multipliers. The main difference between the two methods lies in the time scale at which the interface problem is solved: the micro-time scale for the GC algorithm and macro-time scale for the PH algorithm. During the multi-time-step co-computations involving two finite element codes (explicit and implicit FE codes), the tasks carried out by the coupling software PH-CPL, based on a variant of the PH algorithm, are illustrated and compared to the coupling software GC-CPL based on the GC algorithm. The advantage of the new coupling PH-CPL software is highlighted in terms of parallel capabilities. In addition, the PH-CPL coupling software alleviates the dissipative drawback of the GC method at the interface between the subdomains. Academic cases are investigated to check the energy features and the accuracy order for the GC and PH algorithms. Finally, explicit/implicit multi-time-step co-computations with GC-CPL and PH-CPL software are conducted for two engineering applications under the assumption of linear elastic materials: a reinforced concrete frame structure under blast loading striking its front face and a flat composite stiffened panel subjected to localised loads applied to its central frame. © 2014 Elsevier B.V. All rights reserved. Source

Gravouil A.,Institut Universitaire de France | Combescure A.,CNRS Contacts and Structural Mechanics Laboratory | Brun M.,CNRS Laboratory of Civil and Environmental Engineering
International Journal for Numerical Methods in Engineering

SUMMARY: Computational structural dynamics plays an essential role in the simulation of linear and nonlinear systems. Indeed, the characteristics of the time integration procedure have a critical impact on the feasibility of the calculation. In order to go beyond the classical approach (a unique time integrator and a unique timescale), the pioneer approach of Belytschko and co-workers consisted in developing mixed implicit-explicit time integrators for structural dynamics. In a first step, the implementation and stability analyses of partitioned integrators with one time step have been achieved for a large class of time integrators. In a second step, the implementation and stability analyses of partitioned integrators with different time steps were studied in detail for particular cases. However, stability results involving different time steps and different time integrators in different parts of the mesh is still an open question in the general case for structural dynamics. The aim of this paper is to propose a state-of-the art of heterogeneous (different time schemes) asynchronous (different time steps) time integrators (HATI) for computational structural dynamics. Finally, an alternative approach based on energy considerations (with velocity continuity at the interface) is proposed in order to develop a general class of HATI for structural dynamics. © 2014 John Wiley & Sons, Ltd. Source

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