The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Bas Reedijk - One of the best experts on this subject based on the ideXlab platform.
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XBLOC-PLUS: THE INTERLOCKING, PATTERN PLACED AND EFFICIENT Armour Unit
Coastal Engineering Proceedings, 2020Co-Authors: James Donnelly, Bas Reedijk, Pieter Bakker, Yang Zi QianAbstract:Most breakwaters are built with randomly placed single layer Armour Units as these are most cost-efficient. Most single layer blocks require random Unit orientations, which requires the crane operator to assess the orientation of each individual Unit during placement. DMC noticed the desire for an interlocking block which can be placed in a regular pattern as many crane operators find it easier to place Units uniformly, which requires less intuition. Fifteen years after the introduction of Xbloc, DMC introduces a new interlocking breakwater Armour Unit called XblocPlus which is placed with uniform block orientations.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/oEb1vsYfjL8
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Influence of irregularities in the rock underlayer on the stability of XblocPlus
Coastal Engineering, 2020Co-Authors: Ileen Van Den Berg, Bas Hofland, Bas ReedijkAbstract:Many rubble mound breakwaters are nowadays made with an Armour layer consisting of single layer interlocking elements. The stability of these Armour layers could well be influenced by the irregularity of the rock underlayer, as that influences the degree of interlocking. Especially for the new types of regularly placed Armour, this might be an important factor for the stability. However, this aspect has not been studied widely yet. Therefore, this paper investigates the influence of irregularities in the underlayer on the stability of a type of single layer breakwater elements. Model tests have been conducted in which the irregularities in the underlayer were systematically varied. The irregularities in the underlayer and the orientations of breakwater elements were measured with 3D-scanning. The breakwater Armour Unit used in the tests is the XblocPlus. A new failure mechanism, not previously observed for breakwater elements, was found to initiate damage. Causing the Armour to be pushed outward by a combined effect of the weight of the upper Armour and the excessive hydraulic pressure of the remaining water under the Armour layer. Especially large-scale convex (i.e. protruding outwards) undulations in the cross-shore direction influenced the stability of the Armour layer. This influence has been quantified.
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XBLOC-PLUS – DEVELOPMENT OF A REGULAR PLACED INTERLOCKING Armour Unit
Coastal Engineering Proceedings, 2018Co-Authors: Robert Pieter Michaël Jacobs, Pieter Bakker, Ineke Vos-rovers, Bas ReedijkAbstract:Randomly placed single layer interlocking concrete armor Units are currently the most advanced and cost-efficient option for the protection of breakwaters. The key feature of these Units is the random orientation of the Units, which requires the crane operator to assess the orientation of each individual Unit during block placement. DMC noticed the desire for a block which can be placed in a regular pattern as this will increase the placement rates. Apart of this, regular placement of armor Units can also be preferred for aesthetical reasons. Fifteen years after the introduction of Xbloc, DMC therefore introduces a new breakwater Armour Unit called XblocPlus which is placed with uniform block orientations.
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xbloc plus development of a regular placed interlocking Armour Unit
Coastal Engineering Proceedings, 2018Co-Authors: Robert Pieter Michaël Jacobs, Pieter Bakker, Ineke Vosrovers, Bas ReedijkAbstract:Randomly placed single layer interlocking concrete armor Units are currently the most advanced and cost-efficient option for the protection of breakwaters. The key feature of these Units is the random orientation of the Units, which requires the crane operator to assess the orientation of each individual Unit during block placement. DMC noticed the desire for a block which can be placed in a regular pattern as this will increase the placement rates. Apart of this, regular placement of armor Units can also be preferred for aesthetical reasons. Fifteen years after the introduction of Xbloc, DMC therefore introduces a new breakwater Armour Unit called XblocPlus which is placed with uniform block orientations.
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HYDRAULIC STABILITY AND OVERTOPPING PERFORMANCE OF A NEW TYPE OF REGULAR PLACED ARMOR Unit
Coastal Engineering Proceedings, 2018Co-Authors: Bas Reedijk, Pieter Bakker, Robert Pieter Michaël Jacobs, Tamara Eggeling, Markus MuttrayAbstract:The XblocPlus is a new type of interlocking single layer Armour Units that is placed with uniform orientation. This is novel and different from all other single layer, interlocking Armouring systems. The hydraulic stability of the XblocPlus breakwater Armour Unit was tested in 2D and 3D hydraulic model tests. Wave overtopping tests were performed to determine the roughness coefficients of the EurOtop overtopping formula for the XblocPlus. Model tests on a rubble mound breakwater with XblocPlus Armour included 2D tests with a 1:30 seabed slope and with 1:2 and 3:4 breakwater slopes and 3D model tests with a flat seabed and with a 3:4 breakwater slope. Wave heights up to 150% of the design wave height were tested in the 2D tests and up to 200% with wave directions 0° to 60° in the 3D tests. No Armour Unit displacements were observed in 2D tests with 1:2 slope. In the 2D tests with 3:4 slope one Armour Unit was displaced when the wave height reached 159% of the design wave height. No damage to the XblocPlus Armour layer was observed in the 3D tests. A roughness coefficient of 0.45 was deduced from overtopping tests with wave heights of 60% to 100% of the design wave height. The model test results indicate little or no influence of wave steepness on XblocPlus stability and no adverse influence of wave obliquity while the seabed slope in front of the breakwater may have some impact on the XblocPlus Armour layer stability.
Jiansheng Xiang - One of the best experts on this subject based on the ideXlab platform.
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1 COUPLED FLUIDITY/Y3D TECHNOLOGY AND SIMULATION TOOLS FOR NUMERICAL BREAKWATER MODELLING
2016Co-Authors: Jiansheng Xiang, John-paul Latham, Axelle Viré, Elena Anastasaki, Christopher C. PainAbstract:FEMDEM modelling which combines the multi-body particle interaction and motion modelling (i.e. Discrete Element Model, DEM) with the ability to model internal deformation of arbitrary shape (Finite Element Model, FEM) has been applied to breakwater models. There are two versions of a FEMDEM solver developed; Y3D_D is for deformable materials and is required for dynamic and static stress analysis and Y3D-R is the rigid version often used to numerically construct the Armour Unit packs. This paper also reports the placement protocols: POSITIT. FEMDEM modelling deals with solids interactions and is one modelling component that is to be coupled to other modelling technologies e.g. CFD, interface tracking, wave models, porous media etc. so that the key fluid-solid interactions can be modelled in a full scale virtual breakwater alongside work on scaled hydraulic laboratory models and prototype structures. The latest developments of two-way coupled interactions of waves with coastal structures are also described in this paper
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numerical simulation of breakages of concrete Armour Units using a three dimensional fracture model in the context of the combined finite discrete element method
Computers & Structures, 2015Co-Authors: John-paul Latham, Jiansheng XiangAbstract:Explicit transient dynamic model for 3D multi-body interaction with fracturing.Modelling of fracturing observed in concrete Armour Unit drop and pendulum tests.Modelling collisions, interactions and fracturing of complex-shaped brittle objects.Simulation of various realistic failure modes in complex dynamic stress fields.Development of energy-based analysis tools to identify the degree of fracturing. Rubble-mound breakwaters covered by Armour layers of concrete Units are widely used coastal structures. In this work, a three-dimensional fracture model in the context of the combined finite-discrete element method is applied to investigate the structural integrity of two types of concrete Armour Units under dynamic and extreme loading conditions. Dolosse Units are simulated in drop tests and pendulum tests, and Core-Loc Units of prototype scale are simulated under an imaginary extreme loading condition. The whole structural response of concrete Armour Units is accurately captured and the results provide a better understanding of damage and reserve stability of such systems.
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NUMERICAL MODELLING OF FORCES, STRESSES AND BREAKAGES OF CONCRETE Armour UnitS
Coastal Engineering Proceedings, 2014Co-Authors: John-paul Latham, Jiansheng Xiang, Eleni Anastasaki, Liwei Guo, Nikolaos Karantzoulis, Axelle Viré, Christopher C. PainAbstract:Numerical modelling has the potential to probe the complexity of the interacting physics of rubble mound Armour systems. Through forward modelling of Armour Unit packs, stochastic variables such as Unit displacement and maximum contact force per Unit during an external oscillatory disturbance can be predicted. The combined finite- discrete element method (FEMDEM) is a multi-body method ideally suited to model the behaviour of the Armour layer system and the stresses generated within complex shape Units. In this paper we highlight the latest developments made with the application of FEMDEM technology to breakwater modelling including realistic rock underlayer and concrete Unit layer topologies, maximum contact force distributions, internal Unit stresses, fracture and Unit breakages. Finally, fully coupled wave and multi-body Armour Unit motion with internal dynamic stress generation is illustrated.
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New modelling and analysis methods for concrete Armour Unit systems using FEMDEM
Coastal Engineering, 2013Co-Authors: John-paul Latham, Eleni Anastasaki, Jiansheng XiangAbstract:Abstract Rubble mound breakwaters Armoured with concrete Units rely on collective behaviour between adjacent concrete Armour Units but existing largely empirical approaches have been unable to provide a detailed understanding of how these gigantic granular systems work. The problem has been that current methods cannot investigate the interdependence of hydraulic and structural stability at the scale of individual Units. Numerical methods have the potential to provide such answers but there are many challenges to overcome. We present a solution to the first major bottleneck concerning the solids modelling: the numerical creation of a breakwater trunk section of single layer concrete Units with geometrical and mechanical properties that conform to realistic prototype structure placements. Positioning of Units is achieved with a new versatile software tool, POSITIT, which incorporates user-defined deposition variables and the initial positioning grid necessary to achieve the required design packing densities. The code Y3D, based on the combined finite-discrete element method, FEMDEM, solves the multi-body mechanics of the problem. First, we show numerically constructed breakwater sections with Armour layers of 8 m 3 CORE-LOC™ Units placed on rock underlayers. The numerically-generated packs are deemed acceptable when examined according to a range of criteria indicative of acceptably placed Armour layers, as set by concrete Unit designers. Breakwater sections with packing densities ranging from 0.59 to 0.63 are then created. Using a set of analysis tools, local variation in packing density as an indicator of heterogeneity, centroid spacing, Unit contacts and orientation of Unit axes are presented, together with mechanical information showing the variation in contact forces. For these five packs examined, an increasingly tighter pack was associated with a steady increase in coordination number and a more steeply and accelerating increase in average maximum contact force per Unit. The force distribution results and discussion presented illustrate the potential of discrete Unit FEMDEM modelling methods to address initial placement quality, Armour layer design and future innovation in rubble mound structures.
Hans F. Burcharth - One of the best experts on this subject based on the ideXlab platform.
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Empirical formula for breakage of Dolosse and Tetrapods
Coastal Engineering, 2000Co-Authors: Hans F. Burcharth, J.w. Van Der Meer, K D’angremond, Zhou LiuAbstract:Abstract The slender, complex types of Armour Units, such as Tetrapods and Dolosse are widely used for rubble mound breakwaters. Many failures of such breakwaters were caused by unforeseen early breakage of the Units, thus revealing an inbalance between the strength (structural integrity) of the Units and the hydraulic stability (resistance to displacements) of the Armour layers. Breakage occurs when the stresses from the static, pulsating and impact loads exceeds the tensile strength of the concrete. While the hydraulic stability can be studied in Froude-scale hydraulic model tests, it is not possible to study Armour Unit stresses in small scale models. This is partly because the strain in model Armour Units are too small to be recorded, and partly because the scaling law for impact load generated stresses is nonlinear. The paper discusses the scaling laws related to type of stresses and presents a method which allows studies of Armour Unit stresses by means of a load-cell technique. The technique necessitates impact load response calibration of the load-cell mounted model Armour Units against the equivalent response of prototype or large scale Armour Units. The procedure followed was presented by Burcharth and Liu (Burcharth, H.F., Liu, Z., 1992. Design of Dolos Armour Units. In: Proceedings of the 23rd International Conference on Coastal Engineering, Venice, Italy.) and Burcharth (Burcharth, H.F., 1993. Structural integrity and hydraulic stability of Dolos Armour layers. Series Paper 9, published by the Department of Civil Engineering, Aalborg University, Denmark, 1993.), who also presented design diagram for determination of breakage of Dolosse in trunk sections. The paper presentes an expansion of this work to include breakage of Dolosse in round-heads and Tetrapods in trunk sections. The paper presents a simple dimensional empirical formula instead of diagrams for the estimation of the number of broken Dolosse and Tetrapods in prototype situations, because probabilistic design of breakwaters requires failure mode formulae with the associated uncertainties.
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The Application of load-cell technique in the study of Armour Unit responses to impact loads
1995Co-Authors: Hans F. Burcharth, Zhou LiuAbstract:The slender, complex types of Armour Units, such as Tetrapods and Dolosse are widely used for rubble mound breakwaters. Many of the recent failures of such structures were caused by unforeseen early breakage of the Units, thus revealing an inbalance between the strength (structural integrity) of the Units and the hydraulic stability (resistance to displacements) of the Armour layers. Breakage is caused by stresses from static, pulsating and impact loads. Impact load generated stresses are difficult to investigate due to non-linear scaling laws. The paper describes a method by which impact loads on slender Armour Units can be studied by load-cell technique. Moreover, the paper presents Dolos design diagrams for the prediction of both breakage and hydraulic stability.
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On the determination of concrete Armour Unit stresses including specific results related to Dolosse
Coastal Engineering, 1991Co-Authors: Hans F. Burcharth, Gary L. Howell, Zhou LiuAbstract:Abstract Failures of rubble mound breakwaters Armoured with complex types of unreinforced concrete Armour Units are often due to breakage. This happens when the stresses exceed the material strength. Sufficient parametric studies of the stresses are not yet available to produce design diagrams for structural integrity. The paper presents a general discussion of the problems related to stress determination and describes the results and the analyses of model tests with 200 kg and 200 g load-cell instrumented Dolosse. Static stresses, wave-generated stresses and stresses due to impacts were studied as well as model and scale effects. Moreover, some results from the Crescent City Prototype Dolosse study are presented and related to results from small-scale model tests. A preliminary design diagram for Dolosse is presented as well.
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Stochastic Design of Rubble Mound Breakwaters
System Modelling and Optimization, 1Co-Authors: Søren Nielsen, Hans F. BurcharthAbstract:A level III reliability method for the determination of the optimum mass of a specific concrete Armour Unit for rubble mound breakwaters is presented.
John-paul Latham - One of the best experts on this subject based on the ideXlab platform.
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1 COUPLED FLUIDITY/Y3D TECHNOLOGY AND SIMULATION TOOLS FOR NUMERICAL BREAKWATER MODELLING
2016Co-Authors: Jiansheng Xiang, John-paul Latham, Axelle Viré, Elena Anastasaki, Christopher C. PainAbstract:FEMDEM modelling which combines the multi-body particle interaction and motion modelling (i.e. Discrete Element Model, DEM) with the ability to model internal deformation of arbitrary shape (Finite Element Model, FEM) has been applied to breakwater models. There are two versions of a FEMDEM solver developed; Y3D_D is for deformable materials and is required for dynamic and static stress analysis and Y3D-R is the rigid version often used to numerically construct the Armour Unit packs. This paper also reports the placement protocols: POSITIT. FEMDEM modelling deals with solids interactions and is one modelling component that is to be coupled to other modelling technologies e.g. CFD, interface tracking, wave models, porous media etc. so that the key fluid-solid interactions can be modelled in a full scale virtual breakwater alongside work on scaled hydraulic laboratory models and prototype structures. The latest developments of two-way coupled interactions of waves with coastal structures are also described in this paper
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numerical simulation of breakages of concrete Armour Units using a three dimensional fracture model in the context of the combined finite discrete element method
Computers & Structures, 2015Co-Authors: John-paul Latham, Jiansheng XiangAbstract:Explicit transient dynamic model for 3D multi-body interaction with fracturing.Modelling of fracturing observed in concrete Armour Unit drop and pendulum tests.Modelling collisions, interactions and fracturing of complex-shaped brittle objects.Simulation of various realistic failure modes in complex dynamic stress fields.Development of energy-based analysis tools to identify the degree of fracturing. Rubble-mound breakwaters covered by Armour layers of concrete Units are widely used coastal structures. In this work, a three-dimensional fracture model in the context of the combined finite-discrete element method is applied to investigate the structural integrity of two types of concrete Armour Units under dynamic and extreme loading conditions. Dolosse Units are simulated in drop tests and pendulum tests, and Core-Loc Units of prototype scale are simulated under an imaginary extreme loading condition. The whole structural response of concrete Armour Units is accurately captured and the results provide a better understanding of damage and reserve stability of such systems.
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NUMERICAL MODELLING OF FORCES, STRESSES AND BREAKAGES OF CONCRETE Armour UnitS
Coastal Engineering Proceedings, 2014Co-Authors: John-paul Latham, Jiansheng Xiang, Eleni Anastasaki, Liwei Guo, Nikolaos Karantzoulis, Axelle Viré, Christopher C. PainAbstract:Numerical modelling has the potential to probe the complexity of the interacting physics of rubble mound Armour systems. Through forward modelling of Armour Unit packs, stochastic variables such as Unit displacement and maximum contact force per Unit during an external oscillatory disturbance can be predicted. The combined finite- discrete element method (FEMDEM) is a multi-body method ideally suited to model the behaviour of the Armour layer system and the stresses generated within complex shape Units. In this paper we highlight the latest developments made with the application of FEMDEM technology to breakwater modelling including realistic rock underlayer and concrete Unit layer topologies, maximum contact force distributions, internal Unit stresses, fracture and Unit breakages. Finally, fully coupled wave and multi-body Armour Unit motion with internal dynamic stress generation is illustrated.
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New modelling and analysis methods for concrete Armour Unit systems using FEMDEM
Coastal Engineering, 2013Co-Authors: John-paul Latham, Eleni Anastasaki, Jiansheng XiangAbstract:Abstract Rubble mound breakwaters Armoured with concrete Units rely on collective behaviour between adjacent concrete Armour Units but existing largely empirical approaches have been unable to provide a detailed understanding of how these gigantic granular systems work. The problem has been that current methods cannot investigate the interdependence of hydraulic and structural stability at the scale of individual Units. Numerical methods have the potential to provide such answers but there are many challenges to overcome. We present a solution to the first major bottleneck concerning the solids modelling: the numerical creation of a breakwater trunk section of single layer concrete Units with geometrical and mechanical properties that conform to realistic prototype structure placements. Positioning of Units is achieved with a new versatile software tool, POSITIT, which incorporates user-defined deposition variables and the initial positioning grid necessary to achieve the required design packing densities. The code Y3D, based on the combined finite-discrete element method, FEMDEM, solves the multi-body mechanics of the problem. First, we show numerically constructed breakwater sections with Armour layers of 8 m 3 CORE-LOC™ Units placed on rock underlayers. The numerically-generated packs are deemed acceptable when examined according to a range of criteria indicative of acceptably placed Armour layers, as set by concrete Unit designers. Breakwater sections with packing densities ranging from 0.59 to 0.63 are then created. Using a set of analysis tools, local variation in packing density as an indicator of heterogeneity, centroid spacing, Unit contacts and orientation of Unit axes are presented, together with mechanical information showing the variation in contact forces. For these five packs examined, an increasingly tighter pack was associated with a steady increase in coordination number and a more steeply and accelerating increase in average maximum contact force per Unit. The force distribution results and discussion presented illustrate the potential of discrete Unit FEMDEM modelling methods to address initial placement quality, Armour layer design and future innovation in rubble mound structures.
Chuan-hua Zhu - One of the best experts on this subject based on the ideXlab platform.
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STABILITY OF Armour UnitS ON RUBBLE MOUND BREAKWATER UNDER MULTI-DIRECTIONAL WAVES
Coastal Engineering Journal, 2002Co-Authors: Shuxue Liu, Chuan-hua ZhuAbstract:An extensive 3D model test program has been performed to study the effects of wave obliquity and multidirectionality on the stability of Armour Units on rubble mound breakwater. Four types of Armour Units — dolosse, Accropode, hollow-square and quarry stones were tested under five angles of wave attack (0°, 15°, 30°, 45° and 60°) for both long-crested waves and directional waves. Two wave steepnesses (sop = 0.05 and 0.03) and three directional spreading (s = 10, 40 and ∞) were chosen for the test. A method is proposed to take into account the effects of wave obliquity and multidirectionality on the Armour Unit stability.