CFD and FEA in Civil Engineering: Earthquake, Tunnel, Dam and Geotechnical Multiphysics Simulation

Finite element analysis of Reinforced Concrete

Modelling the damage initiation and propagation until structural failure can be carried out by realistically modelling the geometry and the material behavior of concrete, and individual reinforcement, individually and by defining their complete interconnection. Furthermore, the wide range of advanced special purpose finite element user defined and general-purpose software analysis functionality allows modelling of the structure from construction, through service life to failure. Design and assessment of Service and Ultimate Limit States up to integral failure analysis can be carried out in single FEA software by using advanced method for simulation such complicated and nonlinear material and structure.

Modelling and analysis Include:

• Young hardening concrete with associated cooling
• Nonlinear joints
• Random field material models
• Pre and post tensioning tendons
• Bond-slip between reinforcement and concrete
• Phased analysis for accurate description of load history
• Coupled heat-stress analysis for thermal effects
• Ambient influence on material behavior
• Dynamic analysis
• Dedicated post-processing of crack patterns

Constitutive Material models

• Discrete cracking
• Smeared crack models with fixed and rotating cracks
• Material aging
• Creep and shrinkage models according to different international design codes
• Elasto-plastic models such as Mohr-Coulomb, Drucker- Prager, Rankine
• Maekawa-Fukuura model for cyclic loading
• Von-Mises plasticity with hardening and hysteretic models for steel reinforcement
• User-supplied materials
• Modified two-surface model for cyclic behavior of steel
• Menegotto-Pinto, Monti Nuti, and Dodd Restreppo plasticity models for reinforcements

Finite element simulation of tunnel

With increasing congestion in modern cities, we are turning even more to underground transportation systems. The consequence is not only tunneling under existing structures but, often, tunneling under existing tunnels. Ground movement is an inevitable risk to nearby structures which must be carefully assessed, both at the planning stage and as the project unfolds. This, in addition to the potential negative effect on the safety of construction and the project cost, means that the ability to make these predictions accurately is key. Surface settlement caused by shallow tunnel construction in Greenfield sites can be predicted with some confidence. Surface settlement in urban areas, however, presents a much more complex interaction between the tunnel and its shafts, the ground and the building.

By using the Finite Element Method and correspond special purpose software, it is possible to create detailed 2D and 3D analyses of the interaction between the building, the ground, the tunnel and its shafts. The analysis of existing and new build tunnel linings under the effect of events causing structural damage, freezing, fire, flood, or earthquake are critical to the safety and longevity of the tunnel. With FEA, a model of the tunnel segments and joints, along with the soil and grout pressures upon it, and potential factors listed above, can be analyzed to show intrinsic possible deformations.

Constitutive Material models

• Mohr-Coulomb, Tresca
• Drucker-Prager, Von Mises
• Transversely isotropic
• Duncan-Chang
• Hoek-Brown
• Jointed Rock
• Modified Cam-Clay
• Modified Mohr-Coulomb (Cap model)
• Special interface models
• User supplied subroutine
• Multi-directional fixed crack model
• Total-strain crack models with fixed and rotating cracks
• Fiber reinforced material models
• Creep and shrinkage models

Analysis of Tunnel Include:

• In-situ Stress and Pore-pressure Initialization
• Drained / undrained analysis
• Construction-staged analysis
• Seepage analysis (steady state / transient)
• Saturated or partially saturated flow
• Consolidation analysis (full coupled stress-flow analysis)
• Pressure dependent degree of saturation
• Porosity or saturation dependent permeability
• Deformation dependent density and porosity
• Large displacement and large strain nonlinear analysis
• Special elements for nonlinear modelling of joints between the TBM lining segments
• Eigenvalue analysis (eigenfrequencies, eigenmodes, participation factors, effective masses)
• Direct frequency response analysis
• Modal frequency response analysis
• Spectral response analysis (ABS, SRSS, and CQC modal combinations)
• Linear and nonlinear time domain analysis (total, transient and steady state, solution)
• Various time integration methods, e.g. Newmark, Wilson- theta, Runge-Kutta
• Hybrid frequency-time domain analysis
• Fluid-structure interaction
• Multi-directional base acceleration loads
• Prescribed nodal acceleration loads
• Distributed mass elements (2D line elements + 3D surface elements)
• Bounding/boundary elements for far field behavior (2D line elements + 3D surface elements)
• Viscous, structural, and continuous damping
• Ground freezing analysis including latent heat consumption, thermal expansion and temperature dependent elasto-plasticity
• 2D/3D liquefaction models including user-supplied models
• Generalized plane strain elements for 2D modelling of inclined tunnels or shafts in strongly anisotropic in-situ stresses
• Mesh-independent embedded bars and grids that allow easy modelling of rock bolts, nails or geotextiles in solid soil elements, and reinforcement in beam or shell structural elements
• Soil-structure interaction with nonlinear behavior for both soil and structure
• Transient nonlinear analysis for viscous behavior such as creep, shrinkage or swelling, ambient influence such as temperature or chemical concentration
• Young concrete analysis including hydration heat, shrinkage, hardening, visco-elasticity and cracking

Finite Element Simulation of Dam

Analysis of Dams is one of the specialties that need extensive experience of using material models and analysis capabilities that must be include phased (staged) construction, soil-structure and fluid-structure interaction, user supplied material models, large range of interface models, large displacement and large strain analyses, material non-linearity, time and ambient dependency effects, and nonlinear dynamic analysis.

Dynamic Analysis of Dams Include:

• Direct frequency analysis, modal response analysis, and spectral response analysis, with fluid-structure interaction
• Linear and nonlinear time domain analysis with a wide choice of time integration schemes
• Hybrid frequency-time domain analysis, with possibility to include compressibility of the fluid and bottom absorption
• Multi-directional acceleration loads
• Viscous, structural and continuous damping
• Specified or calculated initial conditions
• Fully coupled consolidation
• Saturated and partially saturated soils
• Steady-state and transient ground-water flow
• Drained/undrained soil
• Phased analysis
• Nonlinear analysis
• Coupled thermo-stress analysis
• Young hardening concrete behavior also with cooling
• Time, temperature and maturity dependency
• Discrete and smeared crack analysis

Constitutive Material models

• Mohr-Coulomb and Drucker-Prager
• Tresca and Von Mises
• Modified Mohr-Coulomb (double-hardening)
• Hoek-Brown and Jointed-rock
• Modified Cam-Clay
• Jardine (London Clay)
• Nonlinear elasticity (Duncan-Chang)
• Smeared crack models with fixed and rotating cracks
• Material aging
• Liquefaction
• Linear, nonlinear and hyper elasticity
• Mohr-Coulomb and Drucker-Prager
• Multi-directional fixed crack model
• Total strain crack models
• Several models for joints
• Viscoelasticity
• Shrinkage
• Linear elastic and plastic reinforcements
• User-supplied materials

Ventilation and Comfort: CFD and FEA Modeling

Fire, Smoke Movement and Explosions

Geotechnical Simulation: FEA based design and optimization for Soil and Rock Engineering

Geotechnical applications and the interaction between the ground and structure, often provide engineers with technically demanding challenges that are best solved with special purpose finite element method software. Finite element method provides a wide range of state-of-the art constitutive models for tackling soil and rock materials in applications as diverse as foundations, embankments, tunnels, excavations, slope stability, mines and dams.

The proposed FEA analysis methods by Enteknograte for pore pressure and consolidation, groundwater flow, earthquake and liquefaction problems are some of the most advanced available and are essential for accurate analysis of these types of coupled problems.

Enteknograte also offers advanced techniques and methodologies based on client needs to model steel and reinforced concrete structures that interact with the ground.

Material models suitable for soil & rock:

• Mohr-Coulomb, Tresca
• Drucker-Prager, Von Mises
• Transversely Isotropic
• Duncan-Chang
• Hoek-Brown
• Jointed rock
• Modified cam-clay
• Modified Mohr-Coulomb (cap model)
• Classic brick
• Special Interface models
• User-supplied subroutine

Geotechnical Analysis Include:

• In-situ stress and pore-pressure initialization
• Construction staged analysis
• Drained/undrained analysis
• Seepage analysis (steady state/transient)
• Saturated or partially saturated flow
• Consolidation analysis (full coupled stress-flow analysis)
• Pressure dependent degree of saturation
• Freely moving phreatic surfaces
• Porosity or saturation dependent permeability
• Deformation dependent density and porosity
• Dynamic (linear and nonlinear) and liquefaction analysis
• Special (embedded) pile elements with nonlinear pile shaft and toe interfaces
• Anchors, nails, and rock bolt modelling
• Geotextiles
• Strength reduction analysis (phi-c)
• Engineering liquefaction

Today, new structures in earthquake sensitive areas are designed to sustain earthquakes without danger of damage or collapse. But if the condition of the structure has been unidentifiably changed, eg. by damage to the structure, deterioration of materials or altered loading, then the effect on earth- quake resistance may be significantly altered.

For many non-standard structures, a proper earthquake design requires a dynamic finite element analysis. For simple assessment, a linear analysis in frequency domain may be sufficient. However, for other applications, the full nonlinear characteristics of possible failure mechanisms and interaction of the structure with ground and environment need to be considered in a nonlinear time stepping analysis

Enteknograte offers solutions for both simple linear dynamic analysis, which can be applied for the design of structures, and also full nonlinear dynamic analysis taking into account the loading history of the structure.

• Linear transient analysis with different time integration schemes
• Direct frequency response analysis
• Modal response analysis & Spectral response analysis
• Nonlinear transient analysis with different time integration schemes
• Hybrid frequency-time domain analysis
• Pushover load & Pushover analysis

All dynamic analysis procedures can be used in combination with fluid-structure interaction effects. At a fluid-structure interface a full coupled acceleration-pressure matrix is calculated for normal displacements on the interface. This interaction matrix accounts for effect of fluid dynamics to the structure in the structural analysis. Frequency dependent effects, e.g. fluid compressibility and boundary damping, can be defined with a range of analysis types.

Specific analysis functions

• Possibility to add stress-stiffness to linear elastic stiffness matrix in frequency analysis
• For direct Frequency Response output of complex results and/or amplitude-phase results
• Lanczos Eigensolver with various decomposition techniques, shifting option, and automatic ordering
• Spectral Response with ABS, SRSS, and CQC output
• Euler backward, Newmark, Wilson-theta, Hilber-Hughes- Taylor, and Runge-Kutta time-integration

Nonlinear materials for earthquake analysis

• Total-strain cracking models
• Maekawa-Fukuura concrete model ( Multi-Axial Damage and Cracked Concrete models)
• Monti-Nuti, Menegotto-Pinto and Dodd-Restreppo-steel models
• Modified 2-surface steel model
• Hardin-Drnevich and Ramberg-Osgood simple soil models
• UBC, Bowl, Nishi and Towhata-Iai liquefaction models
• Engineering liquefaction analysis