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Papers by Nizar Bel Hadj Ali

Research paper thumbnail of Estimation of landfill methane emissions using stochastic search methods

Atmospheric Pollution Research, 2016

Research paper thumbnail of Estimation of Landfill Methane Emissions Using Stochastic Search

Research paper thumbnail of Deployment analysis of a pentagonal tensegrity-ring module

Ring modules are tensegrity systems that include a single strut circuit and recently, they have b... more Ring modules are tensegrity systems that include a single strut circuit and recently, they have been shown to be viable systems for pedestrian bridges. Furthermore, their shape can be controlled using cable actuation. This paper focuses on the deployment of a pentagonal tensegrity-ring module. A geometric study is conducted to identify the deployment-solution space without strut contact. Deployment paths and actuation requirements are explored. The structural response of the module during deployment is analyzed using a modified dynamic relaxation method.

Research paper thumbnail of Une Approche Globale D 'optimisation des Structures Métalliques avec les Algorithmes Génétiques

Research paper thumbnail of Determining control strategies for damage tolerance of an active tensegrity structure

Engineering Structures, 2011

Research paper thumbnail of Designing tensegrity modules for pedestrian bridges

Engineering Structures, 2010

Research paper thumbnail of Estimation of fugitive landfill methane emissions using surface emission monitoring and Genetic Algorithms optimization

Waste Management, 2016

As municipal solid waste (MSW) landfills can generate significant amounts of methane, there is co... more As municipal solid waste (MSW) landfills can generate significant amounts of methane, there is considerable interest in quantifying fugitive methane emissions at such facilities. A variety of methods exist for the estimation of methane emissions from landfills. These methods are either based on analytical emission models or on measurements. This paper presents a method to estimate methane emissions using ambient air methane measurements obtained on the surface of a landfill. Genetic Algorithms based optimization combined with the standard Gaussian dispersion model is employed to identify locations as well as emission rates of potential emission sources throughout a municipal solid waste landfill. Four case studies are employed in order to evaluate the performance of the proposed methodology. It is shown that the proposed approach enables estimation of landfill methane emissions and localization of major emission hotspots in the studied landfills. The proposed source-locating-scheme could be seen as a cost effective method assisting landfill operators to reasonably estimate and locate major methane emissions.

Research paper thumbnail of Comparison of multi-criteria decision methods through a ranking stability index

International Journal of Operational Research, 2016

Research paper thumbnail of Self-Repair of a Tensegrity Pedestrian Bridge through Grouped Actuation

Proceedings of the International Conference on Computing in Civil and Building Engineering Isbn 978 1 907284 60 1, 2010

Research paper thumbnail of Comparison of Two Active Control Strategies on a Tensegrity Structure

Proceedings of the 1st Epfl Doctoral Conference in Mechanics, 2010

Research paper thumbnail of Dynamic analysis and vibration control of an active tensegrity structure

Research paper thumbnail of A transformable tensegrity-footbridge system

Proceedings of the First Conference Transformables 2013 in the Honor of Emilio Perez Pinero, 2013

Research paper thumbnail of Measurement system design for damage detection using model-free data interpretation methods

International Conference on Structural Health Monitoring of Intelligent Infrastructure, 2011

Research paper thumbnail of Deployment of a pentagonal hollow-rope tensegrity module

Research paper thumbnail of Active tensegrity structures with sliding cables – static and dynamic behaviour

Tensegrities are spatial, reticulated and lightweight structures that are increasingly investigat... more Tensegrities are spatial, reticulated and lightweight structures that are increasingly investigated as structural solutions for active and deployable structures. Tensegrity systems are composed only of axially loaded elements providing opportunities for actuation and deployment through changing element lengths. In cable-based actuation strategies, the deficiency of having to control too many cable elements can be overcome by connecting several cables. However, replacing sequences of cable elements by continuous cables sliding over joints significantly changes the mechanics of classical tensegrity structures. Furthermore, challenges emerge for structural analysis, control and actuation. In this paper a modified dynamic relaxation (mDR) algorithm is employed to investigate actuated tensegrity structures with continuous cables. The dynamic behavior of such structures is also investigated.

Research paper thumbnail of Deployment aspects of a tensegrity-ring pedestrian bridge

Tensegrity structures are spatial systems that are composed of tension and compression components... more Tensegrity structures are spatial systems that are composed of tension and compression components in a self-equilibrated prestress stable state. Although tensegrity systems were first introduced in 1950s, few examples have been used for civil engineering purposes. In this paper, tensegrity-ring modules are used for a deployable pedestrian bridge. Ring modules belong to a special family of tensegrity systems composed of a single strut circuit. Assembled in a "hollow-rope" structure, ring modules were shown to be a viable system for a tensegrity pedestrian bridge. Furthermore, ring modules are deployable systems that can change shape by adjusting cable lengths (cable actuation). This paper focuses on the deployment of a tensegrity-ring pedestrian bridge. A geometric study of the deployment for a single module identified the solution space that allows deployment without strut jamming. The optimal deployment path is identified amongst hundreds of possible solutions. Moreover, ...

Research paper thumbnail of Etude comparative des bétons hydrauliques a base de sable siliceux et sable calcaire de concassage

Research paper thumbnail of Design aspects of a deployable tensegrity-hollow-rope footbridge

International Journal of Space Structures, 2012

Research paper thumbnail of Comparing Multi-Criteria Decision aid methods through a ranking stability index

2013 5th International Conference on Modeling, Simulation and Applied Optimization (ICMSAO), 2013

Research paper thumbnail of Configuration of Control System for an Adaptive Tensegrity Structure

ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Volume 1, 2010

ABSTRACT

Research paper thumbnail of Estimation of landfill methane emissions using stochastic search methods

Atmospheric Pollution Research, 2016

Research paper thumbnail of Estimation of Landfill Methane Emissions Using Stochastic Search

Research paper thumbnail of Deployment analysis of a pentagonal tensegrity-ring module

Ring modules are tensegrity systems that include a single strut circuit and recently, they have b... more Ring modules are tensegrity systems that include a single strut circuit and recently, they have been shown to be viable systems for pedestrian bridges. Furthermore, their shape can be controlled using cable actuation. This paper focuses on the deployment of a pentagonal tensegrity-ring module. A geometric study is conducted to identify the deployment-solution space without strut contact. Deployment paths and actuation requirements are explored. The structural response of the module during deployment is analyzed using a modified dynamic relaxation method.

Research paper thumbnail of Une Approche Globale D 'optimisation des Structures Métalliques avec les Algorithmes Génétiques

Research paper thumbnail of Determining control strategies for damage tolerance of an active tensegrity structure

Engineering Structures, 2011

Research paper thumbnail of Designing tensegrity modules for pedestrian bridges

Engineering Structures, 2010

Research paper thumbnail of Estimation of fugitive landfill methane emissions using surface emission monitoring and Genetic Algorithms optimization

Waste Management, 2016

As municipal solid waste (MSW) landfills can generate significant amounts of methane, there is co... more As municipal solid waste (MSW) landfills can generate significant amounts of methane, there is considerable interest in quantifying fugitive methane emissions at such facilities. A variety of methods exist for the estimation of methane emissions from landfills. These methods are either based on analytical emission models or on measurements. This paper presents a method to estimate methane emissions using ambient air methane measurements obtained on the surface of a landfill. Genetic Algorithms based optimization combined with the standard Gaussian dispersion model is employed to identify locations as well as emission rates of potential emission sources throughout a municipal solid waste landfill. Four case studies are employed in order to evaluate the performance of the proposed methodology. It is shown that the proposed approach enables estimation of landfill methane emissions and localization of major emission hotspots in the studied landfills. The proposed source-locating-scheme could be seen as a cost effective method assisting landfill operators to reasonably estimate and locate major methane emissions.

Research paper thumbnail of Comparison of multi-criteria decision methods through a ranking stability index

International Journal of Operational Research, 2016

Research paper thumbnail of Self-Repair of a Tensegrity Pedestrian Bridge through Grouped Actuation

Proceedings of the International Conference on Computing in Civil and Building Engineering Isbn 978 1 907284 60 1, 2010

Research paper thumbnail of Comparison of Two Active Control Strategies on a Tensegrity Structure

Proceedings of the 1st Epfl Doctoral Conference in Mechanics, 2010

Research paper thumbnail of Dynamic analysis and vibration control of an active tensegrity structure

Research paper thumbnail of A transformable tensegrity-footbridge system

Proceedings of the First Conference Transformables 2013 in the Honor of Emilio Perez Pinero, 2013

Research paper thumbnail of Measurement system design for damage detection using model-free data interpretation methods

International Conference on Structural Health Monitoring of Intelligent Infrastructure, 2011

Research paper thumbnail of Deployment of a pentagonal hollow-rope tensegrity module

Research paper thumbnail of Active tensegrity structures with sliding cables – static and dynamic behaviour

Tensegrities are spatial, reticulated and lightweight structures that are increasingly investigat... more Tensegrities are spatial, reticulated and lightweight structures that are increasingly investigated as structural solutions for active and deployable structures. Tensegrity systems are composed only of axially loaded elements providing opportunities for actuation and deployment through changing element lengths. In cable-based actuation strategies, the deficiency of having to control too many cable elements can be overcome by connecting several cables. However, replacing sequences of cable elements by continuous cables sliding over joints significantly changes the mechanics of classical tensegrity structures. Furthermore, challenges emerge for structural analysis, control and actuation. In this paper a modified dynamic relaxation (mDR) algorithm is employed to investigate actuated tensegrity structures with continuous cables. The dynamic behavior of such structures is also investigated.

Research paper thumbnail of Deployment aspects of a tensegrity-ring pedestrian bridge

Tensegrity structures are spatial systems that are composed of tension and compression components... more Tensegrity structures are spatial systems that are composed of tension and compression components in a self-equilibrated prestress stable state. Although tensegrity systems were first introduced in 1950s, few examples have been used for civil engineering purposes. In this paper, tensegrity-ring modules are used for a deployable pedestrian bridge. Ring modules belong to a special family of tensegrity systems composed of a single strut circuit. Assembled in a "hollow-rope" structure, ring modules were shown to be a viable system for a tensegrity pedestrian bridge. Furthermore, ring modules are deployable systems that can change shape by adjusting cable lengths (cable actuation). This paper focuses on the deployment of a tensegrity-ring pedestrian bridge. A geometric study of the deployment for a single module identified the solution space that allows deployment without strut jamming. The optimal deployment path is identified amongst hundreds of possible solutions. Moreover, ...

Research paper thumbnail of Etude comparative des bétons hydrauliques a base de sable siliceux et sable calcaire de concassage

Research paper thumbnail of Design aspects of a deployable tensegrity-hollow-rope footbridge

International Journal of Space Structures, 2012

Research paper thumbnail of Comparing Multi-Criteria Decision aid methods through a ranking stability index

2013 5th International Conference on Modeling, Simulation and Applied Optimization (ICMSAO), 2013

Research paper thumbnail of Configuration of Control System for an Adaptive Tensegrity Structure

ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Volume 1, 2010

ABSTRACT