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Permeability of virtual cement seems to exceed experimental data by several orders of magnitude. The differences may actually not be that dramatic, since experimental samples are in practice not always fully saturated as generally assumed. This paper demonstrates that this has enormous effects on permeability. A numerical study is conducted on water permeability of partially saturated cement paste based on simulated microstructures. During drying, larger pores empty first according to the Kelvin-Laplace law, leading to a significant decline in water permeability. The results in terms of relative water permeability have been validated against lattice Boltzmann simulations and experimental data, respectively. A satisfactory agreement is found. Both the pore size distribution and pore connectivity are shown to have an important influence on the overall permeability. The effects of technological parameters, such as hydration age and water-to-cement ratio, have also been discussed., Structural Engineering, Civil Engineering and Geosciences

This paper presents a new damage model for simulating fatigue-driven delamination in composite laminates. This model is developed based on the Thick Level Set approach (TLS) and provides a favorable link between damage mechanics and fracture mechanics through the non-local evaluation of the energy release rate. Previously, this approach has been applied in the context of quasi-static continuum damage models. In this work, the thick level set method is translated to an interface model. The new interface damage model can be applied to quasistatic and fatigue simulations. It benefits from the kinematic flexibility of interface elements and preferable use of fracture mechanics for fatigue analysis. A 3D model is developed based on this approach and the obtained numerical results are validated with analytical and experimental data., Structural Engineering, Civil Engineering and Geosciences

Thick laminates are increasingly present in large composites structures such as wind turbine blades. Different factors are suspected to be involved in the decreased static and dynamic performance of thick laminates. These include the effect of self-heating, the scaling effect, and the manufacturing process influence. The aim of this work is to study the through thickness variation of static and dynamic lamina properties in thick laminates. For this purpose, 60-70 mm thick unidirectional GFRP/epoxy infused panels were divided in sub-laminates with the help of peel-ply layers at different thickness positions. From each sub-laminate, 4 mm thick compression coupons with integrated tabs and tension coupons were manufactured. In order to characterize the manufacturing influence, the 60-70 mm thick laminates plates were monitored during the manufacturing. Static and fatigue tests were carried out for each sub-laminate in order to study the lamina properties at different thicknesses positions through the thickness. The present work reports temperature profiles and residual stress measurements through the thickness recorded during the manufacturing, as well as experimental data from static and fatigue tests (S-N curves) of sub-laminates obtained at different thickness positions., Structural Engineering, Civil Engineering and Geosciences

The development of realistic numerical tools to efficiently model the response of concrete structures subjected to close-in detonations and high velocity impacts has been one of the major quests in defense research. Under these loading conditions, quasi-brittle materials undergo a multitude of failure (damage) mechanisms. Dynamic tensile failure (e.g. spalling), characterized by a significant strength increase associated with loading rate, has revealed to be particularly challenging to represent. This phenomenon has been modeled by means of continuous damage mechanics in the last decades. To minimize pathological mesh sensitivity, a nonlocal formulation is generally considered. Nevertheless, these models fail to properly represent damage initiation and growth around discontinuities, such as notches, damage areas and free boundaries. These inconsistencies are the consequence of using a fixed interaction domain (characteristic length) in the nonlocal formulation. In spite of limited experimental knowledge about the definition of the characteristic length parameter, there is now consensus that this quantity is not constant. In this contribution, an enhanced nonlocal model, where the interaction domain of any gauss point contracts or expands according to the stress-state of its neighbors, is used. This formulation was coupled to the well-known Mazars damage model and implemented within the framework of LS-DYNA using a fully explicit computation scheme. Two sets of numerical studies are presented in this paper. One shows the applicability and limitations of the implemented explicit algorithm to compute nonlocal quantities. The other shows that with this stress-enhanced regularization model it is possible to represent damage initiation and growth more realistically and correct the inconsistencies emerging from the traditional nonlocal formulations., Structural Engineering, Civil Engineering and Geosciences

Details of a complete methodology for porosimetry of virtual concrete have been described in a series of publications. This paper shortly sketches the main characteristics, whereupon it is indicated how a pore network model is designed based on data extracted from the virtual cement paste. This involves smoothing the main trunks as the main pore connections between outer surfaces. Network estimates for water transport through concrete is presented and shown exceeding commonly used MIP estimates. For quantitative image analysis results the gap will be much smaller, though. Moreover, experimental data are biased by continued hydration (self-healing effects). Some simple examples are presented to improve the insight into the methodology. Moreover, they can additionally serve as validation by comparing estimates with analytical results., Structural Engineering, Civil Engineering and Geosciences

Permeability of virtual cement seems to exceed experimental data by several orders of magnitude. The differences may actually not be that dramatic, since experimental samples are in practice not always fully saturated as generally assumed. This paper demonstrates that this has enormous effects on permeability. A numerical study is conducted on water permeability of partially saturated cement paste based on simulated microstructures. During drying, larger pores empty first according to the Kelvin-Laplace law, leading to a significant decline in water permeability. The results in terms of relative water permeability have been validated against lattice Boltzmann simulations and experimental data, respectively. A satisfactory agreement is found. Both the pore size distribution and pore connectivity are shown to have an important influence on the overall permeability. The effects of technological parameters, such as hydration age and water-to-cement ratio, have also been discussed., Structural Engineering, Civil Engineering and Geosciences

Thick laminates are increasingly present in large composites structures such as wind turbine blades. Different factors are suspected to be involved in the decreased static and dynamic performance of thick laminates. These include the effect of self-heating, the scaling effect, and the manufacturing process influence. The aim of this work is to study the through thickness variation of static and dynamic lamina properties in thick laminates. For this purpose, 60-70 mm thick unidirectional GFRP/epoxy infused panels were divided in sub-laminates with the help of peel-ply layers at different thickness positions. From each sub-laminate, 4 mm thick compression coupons with integrated tabs and tension coupons were manufactured. In order to characterize the manufacturing influence, the 60-70 mm thick laminates plates were monitored during the manufacturing. Static and fatigue tests were carried out for each sub-laminate in order to study the lamina properties at different thicknesses positions through the thickness. The present work reports temperature profiles and residual stress measurements through the thickness recorded during the manufacturing, as well as experimental data from static and fatigue tests (S-N curves) of sub-laminates obtained at different thickness positions., Structural Engineering, Civil Engineering and Geosciences

This paper presents a new damage model for simulating fatigue-driven delamination in composite laminates. This model is developed based on the Thick Level Set approach (TLS) and provides a favorable link between damage mechanics and fracture mechanics through the non-local evaluation of the energy release rate. Previously, this approach has been applied in the context of quasi-static continuum damage models. In this work, the thick level set method is translated to an interface model. The new interface damage model can be applied to quasistatic and fatigue simulations. It benefits from the kinematic flexibility of interface elements and preferable use of fracture mechanics for fatigue analysis. A 3D model is developed based on this approach and the obtained numerical results are validated with analytical and experimental data., Structural Engineering, Civil Engineering and Geosciences

The development of realistic numerical tools to efficiently model the response of concrete structures subjected to close-in detonations and high velocity impacts has been one of the major quests in defense research. Under these loading conditions, quasi-brittle materials undergo a multitude of failure (damage) mechanisms. Dynamic tensile failure (e.g. spalling), characterized by a significant strength increase associated with loading rate, has revealed to be particularly challenging to represent. This phenomenon has been modeled by means of continuous damage mechanics in the last decades. To minimize pathological mesh sensitivity, a nonlocal formulation is generally considered. Nevertheless, these models fail to properly represent damage initiation and growth around discontinuities, such as notches, damage areas and free boundaries. These inconsistencies are the consequence of using a fixed interaction domain (characteristic length) in the nonlocal formulation. In spite of limited experimental knowledge about the definition of the characteristic length parameter, there is now consensus that this quantity is not constant. In this contribution, an enhanced nonlocal model, where the interaction domain of any gauss point contracts or expands according to the stress-state of its neighbors, is used. This formulation was coupled to the well-known Mazars damage model and implemented within the framework of LS-DYNA using a fully explicit computation scheme. Two sets of numerical studies are presented in this paper. One shows the applicability and limitations of the implemented explicit algorithm to compute nonlocal quantities. The other shows that with this stress-enhanced regularization model it is possible to represent damage initiation and growth more realistically and correct the inconsistencies emerging from the traditional nonlocal formulations., Structural Engineering, Civil Engineering and Geosciences

Details of a complete methodology for porosimetry of virtual concrete have been described in a series of publications. This paper shortly sketches the main characteristics, whereupon it is indicated how a pore network model is designed based on data extracted from the virtual cement paste. This involves smoothing the main trunks as the main pore connections between outer surfaces. Network estimates for water transport through concrete is presented and shown exceeding commonly used MIP estimates. For quantitative image analysis results the gap will be much smaller, though. Moreover, experimental data are biased by continued hydration (self-healing effects). Some simple examples are presented to improve the insight into the methodology. Moreover, they can additionally serve as validation by comparing estimates with analytical results., Structural Engineering, Civil Engineering and Geosciences

In this contribution, dual and primal domain decomposition techniques are studied for the multiscale analysis of failure in quasi-brittle materials. The multiscale strategy essentially consists in decomposing the structure into a number of nonoverlapping domains and considering a refined spatial resolution where needed. In multiscale analysis of damage, the spatial refinement is performed where damage nucleation and propagation take place. The domain decomposition approach turns to be a computationally cheaper alternative to the direct numerical solution in which a fine scale model is considered throughout the complete sample. Dual and primal domain decomposition techniques are appropriate for such concurrent multiscale analyses and provide identical results. Parallel scalability of the multiscale analysis is studied using a moderate number of processors and a parallel direct solver for the system obtained through the assembly of all domains., Structural Engineering, Civil Engineering and Geosciences

On the microlevel, cusps are formed during delamination crack growth under mode II loading conditions. In this work, two different approaches to simulate this process are presented. Firstly a cohesive zone method where cohesive segments are introduced between a pair of neighbouring elements when the traction between those elements exceeds the strength. And secondly the thick level set method, which allows for a staggered solution scheme. Both methods successfully predict the inclined cracks that form initially if constitutive laws are chosen carefully, but both have difficulties to simulate final failure., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

In this contribution, dual and primal domain decomposition techniques are studied for the multiscale analysis of failure in quasi-brittle materials. The multiscale strategy essentially consists in decomposing the structure into a number of nonoverlapping domains and considering a refined spatial resolution where needed. In multiscale analysis of damage, the spatial refinement is performed where damage nucleation and propagation take place. The domain decomposition approach turns to be a computationally cheaper alternative to the direct numerical solution in which a fine scale model is considered throughout the complete sample. Dual and primal domain decomposition techniques are appropriate for such concurrent multiscale analyses and provide identical results. Parallel scalability of the multiscale analysis is studied using a moderate number of processors and a parallel direct solver for the system obtained through the assembly of all domains., Structural Engineering, Civil Engineering and Geosciences

On the microlevel, cusps are formed during delamination crack growth under mode II loading conditions. In this work, two different approaches to simulate this process are presented. Firstly a cohesive zone method where cohesive segments are introduced between a pair of neighbouring elements when the traction between those elements exceeds the strength. And secondly the thick level set method, which allows for a staggered solution scheme. Both methods successfully predict the inclined cracks that form initially if constitutive laws are chosen carefully, but both have difficulties to simulate final failure., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

Experimental testing and numerical analysis often travel in tandem in a design process. Recent advances in novel numerical techniques to simulate mesh objective crack propagation offer a great potential for accurate and efficient damage analysis of composite laminates. This paper presents a numerical study on computational modeling of mesh independent matrix cracking and delamination in laminated composite plates subjected to out-of-plane loading. The analyses are performed with emphasis on a better understanding of the damage development and the interaction between different damage mechanisms. In particular, the effect of fibre orientation, the interface material properties and splitting cracks on damage development and overall response of the laminate are studied., Structural Engineering, Civil Engineering and Geosciences

Experimental testing and numerical analysis often travel in tandem in a design process. Recent advances in novel numerical techniques to simulate mesh objective crack propagation offer a great potential for accurate and efficient damage analysis of composite laminates. This paper presents a numerical study on computational modeling of mesh independent matrix cracking and delamination in laminated composite plates subjected to out-of-plane loading. The analyses are performed with emphasis on a better understanding of the damage development and the interaction between different damage mechanisms. In particular, the effect of fibre orientation, the interface material properties and splitting cracks on damage development and overall response of the laminate are studied., Structural Engineering, Civil Engineering and Geosciences

The multiscale framework presented in [1, 2] is assessed in this contribution for a study of random heterogeneous materials. Results are compared to direct numerical simulations (DNS) and the sensitivity to user-defined parameters such as the domain decomposition type and initial coarse scale resolution is reported. The parallel performance of the implementation is studied for different domain decompositions., Structural Engineering, Civil Engineering and Geosciences

Advanced Finite Element codes provide the possibility to simulate high rate loading on concrete targets as ballistic impact and explosions. Although damage to RC structures due to these loadings can be simulated and detailed results can be obtained the predictions are still far from perfect. It is well known that the results strongly depend on the numerical material model. In a collaboration project of AFA, IST, Delft University of Technology and TNO damage prediction in concrete panels due to close in explosions and the residual bearing capacity are studied. The hydrodynamic finite element computer code (Hydrocode) LS-DYNA was chosen as the computational tool to pursue this research. The first step was the comparison and analysis of the three most advanced concrete models implemented in LS-DYNA: Karagozian & Case Concrete model (KCC), Continuous Surface Cap Model (CSCM) and Riedel, Hiermaier and Thoma (RHT) model. The models were tested under a wide range of configurations in order to evaluate their response under different stress states and loading rates. In this paper our attentions are focus on the damage development in compression and tension. Bar tests were modelled in order to explore the material model’s dynamic response in a more controlled way., Structural Engineering, Civil Engineering and Geosciences

Macroscopic behavior of quasi-brittle materials is determined by their heterogeneous microstructure. Initiation and propagation of cracks are controlled by the randomness of the material and occur at different length scales (figure 1). Multi-scale approaches provide methodologies to obtain the mechanical behavior of a heterogeneous material from a local scale response. The present project deals with developing an objective multiscale method to model cracking in heterogeneous materials under high frequency loading conditions., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

Modelling fracture in concrete or masonry is known to be problematic regarding the robustness of iterative solution procedures and, the use of non-iterative methods (or that minimize the use of iterations) in quasi-brittle materials is now under strong development, due to the necessity to obtain effective results in finite element analysis [1, 2] where strong non-linearities emerge that are otherwise unwieldy to model. In the proposed lecture, two new methods designated as Non-Iterative Energy based Method (NIEM) and Automatic presented in [1, 3] are applied with extension to modelling damage-plastic behaviour. The new methods combine an incremental-total procedure with the preferential use of incremental steps, switching to the total approach only at critical bifurcation points. The development of the load-unloading abilities is allowed by these incremental/total methods, which take advantage of keeping the material’s stress/strain memory due to the preferential use of an incremental procedure. A new approach to the unload-load cycles is used in the scope of a noniterative procedure, which will mitigate the numerical difficulties inherent to cyclic loading. The formulation for both methods for structures with both softening and hardening behaviour is presented and a structural example where the numerical results are compared with experimental results., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

Security-sensitive structures, such as military facilities, government buildings, strategic industrial infrastructures, bridges, dams, etc. should be designed to withstand explosions and high velocity impacts, both from terrorist attacks and other acts of war. Since concrete is the most widely used construction material understanding concrete material behaviour under high strain loading rates is crucial, Structural Engineering, Civil Engineering and Geosciences

A multi-scale numerical approach for modeling cracking in heterogeneous quasi-brittle materials under dynamic loading is presented. In the model, a discontinuous crack model is used at macro-scale to simulate fracture and a gradient-enhanced damage model has been used at meso-scale to simulate diffuse damage. The traction-separation law for the cohesive zone model at macro-scale is obtained from the meso-scale information through the discontinuous computational homogenization method. The method is based on the so-called failure zone averaging scheme in which the averaging theorem is used over the active damaged zone of the meso-scale. Objectivity with respect to the local-scale sample size in the softening regime is obtained in this fashion. In order to evaluate the macroscopic traction at each integration point on the crack, at each time step of the macro model solution, a static boundary value problem is solved for the representative volume element (RVE) whose size is much smaller than the macro length-scale and the macroscopic wave-length. The effect of the crack opening rate on the macro cohesive law is taken into account by relating the material properties of the meso-scale model to the macro crack opening rate. The objectivity of the model response with respect to the representative volume element (RVE) size is demonstrated for wave propagation problems. The rate-dependent multi-scale model is then verified by comparison with a direct numerical simulation (DNS)., Structural Engineering, Civil Engineering and Geosciences

A mesoscopic masonry model is presented using the partition of unity finite element method. Joints are only explicitly introduced when a critical stress state is exceeded, resulting in a computationally more efficient procedure when compared to models in which all joints are a priori active. The performance of the presented model is demonstrated by several numerical examples., Structural Engineering, Civil Engineering and Geosciences

This contribution discusses a coupled two-scale framework for hydro-mechanical problems in saturated heterogeneous porous geomaterials. The heterogeneous nature of such materials can lead to an anisotropy of the hydro-mechanical couplings and non-linear effects. Based on an assumed model of the mesostructure, the average macroscopic hydro-mechanical behaviour is extracted by means of a computational homogenisation procedure in a monolithic way. The ingredients needed to upscale the hydro-mechanical couplings are outlined. The two-scale simulation results are compared with direct numerical simulation for the consolidation of a particle-matrix porous material., Structural Engineering, Civil Engineering and Geosciences

Numerical analysis of progressive damage in fiber-reinforced laminated composite plates is a challenge due to the presence of different, complex failure mechanisms and their mutual interaction. A meso-scopic progressive failure model is presented to simulate interacting damage mechanisms (matrix cracking and delamination) in laminated composite plates., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

In this contribution, a finite element model for simulating coupled hydromechanic and electrokinetic flow in a multiphase domain is outlined. The model describes CO2 flow in a deformed, unsaturated geological formation and its associated streaming potential flow. The governing field equations are derived based on the averaging theory and solved numerically based a mixed discretization scheme. The standard Galerkin finite element method is utilized to discretize the deformation and the diffusive dominant field equations, and the extended finite element method, together with the level-set method, is utilized to discretize the advective dominant field equations. The level-set method is employed to trace the CO2 plume front, and the extended finite element method is employed to model the high gradient in the saturation field front. The mixed discretization scheme leads to a highly convergent system, giving a stable and effectively mesh-independent model. The capability of the model is evaluated by verification and numerical examples. The numerical analysis shows that the streaming potential peak moves with the saturation front, and hence, measuring the streaming potential can be utilized for monitoring CO2 flow remotely., Structural Engineering, Civil Engineering and Geosciences

Some polymers are not only transparent and lightweight, but also impact and ballistic resistant. Designing and preparing such polymeric materials with a high impact?resistant performance is of importance to e.g. aviation, military and windscreen applications., Structural Engineering, Civil Engineering and Geosciences

Macroscopic behavior of quasi-brittle materials is determined by their heterogeneous microstructure. Initiation and propagation of cracks are controlled by the randomness of the material and occur at different length scales (figure 1). Multi-scale approaches provide methodologies to obtain the mechanical behavior of a heterogeneous material from a local scale response. The present project deals with developing an objective multiscale method to model cracking in heterogeneous materials under high frequency loading conditions., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

The multiscale framework presented in [1, 2] is assessed in this contribution for a study of random heterogeneous materials. Results are compared to direct numerical simulations (DNS) and the sensitivity to user-defined parameters such as the domain decomposition type and initial coarse scale resolution is reported. The parallel performance of the implementation is studied for different domain decompositions., Structural Engineering, Civil Engineering and Geosciences

Modelling fracture in concrete or masonry is known to be problematic regarding the robustness of iterative solution procedures and, the use of non-iterative methods (or that minimize the use of iterations) in quasi-brittle materials is now under strong development, due to the necessity to obtain effective results in finite element analysis [1, 2] where strong non-linearities emerge that are otherwise unwieldy to model. In the proposed lecture, two new methods designated as Non-Iterative Energy based Method (NIEM) and Automatic presented in [1, 3] are applied with extension to modelling damage-plastic behaviour. The new methods combine an incremental-total procedure with the preferential use of incremental steps, switching to the total approach only at critical bifurcation points. The development of the load-unloading abilities is allowed by these incremental/total methods, which take advantage of keeping the material’s stress/strain memory due to the preferential use of an incremental procedure. A new approach to the unload-load cycles is used in the scope of a noniterative procedure, which will mitigate the numerical difficulties inherent to cyclic loading. The formulation for both methods for structures with both softening and hardening behaviour is presented and a structural example where the numerical results are compared with experimental results., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

Security-sensitive structures, such as military facilities, government buildings, strategic industrial infrastructures, bridges, dams, etc. should be designed to withstand explosions and high velocity impacts, both from terrorist attacks and other acts of war. Since concrete is the most widely used construction material understanding concrete material behaviour under high strain loading rates is crucial, Structural Engineering, Civil Engineering and Geosciences

A multi-scale numerical approach for modeling cracking in heterogeneous quasi-brittle materials under dynamic loading is presented. In the model, a discontinuous crack model is used at macro-scale to simulate fracture and a gradient-enhanced damage model has been used at meso-scale to simulate diffuse damage. The traction-separation law for the cohesive zone model at macro-scale is obtained from the meso-scale information through the discontinuous computational homogenization method. The method is based on the so-called failure zone averaging scheme in which the averaging theorem is used over the active damaged zone of the meso-scale. Objectivity with respect to the local-scale sample size in the softening regime is obtained in this fashion. In order to evaluate the macroscopic traction at each integration point on the crack, at each time step of the macro model solution, a static boundary value problem is solved for the representative volume element (RVE) whose size is much smaller than the macro length-scale and the macroscopic wave-length. The effect of the crack opening rate on the macro cohesive law is taken into account by relating the material properties of the meso-scale model to the macro crack opening rate. The objectivity of the model response with respect to the representative volume element (RVE) size is demonstrated for wave propagation problems. The rate-dependent multi-scale model is then verified by comparison with a direct numerical simulation (DNS)., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

This contribution discusses a coupled two-scale framework for hydro-mechanical problems in saturated heterogeneous porous geomaterials. The heterogeneous nature of such materials can lead to an anisotropy of the hydro-mechanical couplings and non-linear effects. Based on an assumed model of the mesostructure, the average macroscopic hydro-mechanical behaviour is extracted by means of a computational homogenisation procedure in a monolithic way. The ingredients needed to upscale the hydro-mechanical couplings are outlined. The two-scale simulation results are compared with direct numerical simulation for the consolidation of a particle-matrix porous material., Structural Engineering, Civil Engineering and Geosciences

A mesoscopic masonry model is presented using the partition of unity finite element method. Joints are only explicitly introduced when a critical stress state is exceeded, resulting in a computationally more efficient procedure when compared to models in which all joints are a priori active. The performance of the presented model is demonstrated by several numerical examples., Structural Engineering, Civil Engineering and Geosciences

Numerical analysis of progressive damage in fiber-reinforced laminated composite plates is a challenge due to the presence of different, complex failure mechanisms and their mutual interaction. A meso-scopic progressive failure model is presented to simulate interacting damage mechanisms (matrix cracking and delamination) in laminated composite plates., Structural Engineering, Civil Engineering and Geosciences

Experimental testing and numerical analysis often travel in tandem in a design process. Recent advances in novel numerical techniques to simulate mesh objective crack propagation offer a great potential for accurate and efficient damage analysis of composite laminates. This paper presents a numerical study on computational modeling of mesh independent matrix cracking and delamination in laminated composite plates subjected to out-of-plane loading. The analyses are performed with emphasis on a better understanding of the damage development and the interaction between different damage mechanisms. In particular, the effect of fibre orientation, the interface material properties and splitting cracks on damage development and overall response of the laminate are studied., Structural Engineering, Civil Engineering and Geosciences

In this contribution, a finite element model for simulating coupled hydromechanic and electrokinetic flow in a multiphase domain is outlined. The model describes CO2 flow in a deformed, unsaturated geological formation and its associated streaming potential flow. The governing field equations are derived based on the averaging theory and solved numerically based a mixed discretization scheme. The standard Galerkin finite element method is utilized to discretize the deformation and the diffusive dominant field equations, and the extended finite element method, together with the level-set method, is utilized to discretize the advective dominant field equations. The level-set method is employed to trace the CO2 plume front, and the extended finite element method is employed to model the high gradient in the saturation field front. The mixed discretization scheme leads to a highly convergent system, giving a stable and effectively mesh-independent model. The capability of the model is evaluated by verification and numerical examples. The numerical analysis shows that the streaming potential peak moves with the saturation front, and hence, measuring the streaming potential can be utilized for monitoring CO2 flow remotely., Structural Engineering, Civil Engineering and Geosciences

Structural Engineering, Civil Engineering and Geosciences

Advanced Finite Element codes provide the possibility to simulate high rate loading on concrete targets as ballistic impact and explosions. Although damage to RC structures due to these loadings can be simulated and detailed results can be obtained the predictions are still far from perfect. It is well known that the results strongly depend on the numerical material model. In a collaboration project of AFA, IST, Delft University of Technology and TNO damage prediction in concrete panels due to close in explosions and the residual bearing capacity are studied. The hydrodynamic finite element computer code (Hydrocode) LS-DYNA was chosen as the computational tool to pursue this research. The first step was the comparison and analysis of the three most advanced concrete models implemented in LS-DYNA: Karagozian & Case Concrete model (KCC), Continuous Surface Cap Model (CSCM) and Riedel, Hiermaier and Thoma (RHT) model. The models were tested under a wide range of configurations in order to evaluate their response under different stress states and loading rates. In this paper our attentions are focus on the damage development in compression and tension. Bar tests were modelled in order to explore the material model’s dynamic response in a more controlled way., Structural Engineering, Civil Engineering and Geosciences