Concrete & Geomaterial Modeling with LS-DYNA®
- Dr. Len Schwer
Concrete & Geomaterial Modeling with LS-DYNA®
You should be familiar with LS-DYNA.
Constitutive models for concrete and geomaterials (rocks and soil) are typically based on the same mathematical plasticity theory framework used to model common metals. However, the constitutive behavior of concrete and geomaterials differs from that of metals in three important ways:
- They are (relatively) highly compressible,that is, a pressure-volume response;
- Their yield strength depends on the mean stress (pressure), that is, a frictional response; and
- Their tensile strengths are small compared to their compressive strengths.
These basic differences give rise to interesting aspects of constitutive modeling that may not be familiar to engineers trained in classical metal plasticity.
This course starts from the common ground of introductory metal plasticity constitutive modeling and successively builds on this base by adding the constitutive modeling features necessary to model concrete and geomaterials. The LS-DYNA constitutive models covered are adequate for modeling most types of rock, all concretes, and a large class of soils. This course is intended for those new to concrete and geomaterial constitutive modeling but will also be useful to those seeking a more in-depth explanation of the LS-DYNA concrete and geomaterial constitutive models covered.
A significant portion of the course is devoted to understanding the types of laboratory tests and data that are available to characterize concrete and geomaterials. Unlike most metals, whose strength is characterized by a single value obtained from a simple uniaxial stress test, concrete and geomaterial characterization requires a matrix of laboratory tests. Knowledge of how these tests are performed, the form and format of typical laboratory test data, and the interpretation of the data for use with a concrete or geomaterial constitutive model, is essential to becoming a successful concrete and geomaterial modeler.
The basic mathematics of the LS-DYNA concrete and geomaterials constitutive models are covered, with an emphasis on how the mathematics can aid the modeler in fitting constitutive models to the available laboratory data. The mechanics of the constitutive model are emphasized to provide the modeler with the insights necessary to easily separate cause and effect in these complicated constitutive models. Exercises in fitting the LS-DYNA concrete and geomaterial constitutive models to typical laboratory data are used to illustrate the data and the constitutive models.
Several application case studies are covered:
- quasi-static soil penetration,
- quasi-static eccentric loading of a reinforced concrete column,
- penetration of a concrete target using Lagrange with erosion, Eulerian, and SPH formulations, and
- blast loading of a reinforced concrete slab modeled with several concrete models.
Introduction to Metal Plasticity
- von Mises Constitutive Model (*MAT_003)
- Perfect Plasticity and Hardening
- Overview of a Numerical Constitutive Model Algorithm
- Tresca Yield Criterion
- Description of the Pi-Plane
- Two Special Limiting Cases for the Lode Angle
Introduction to Geomaterials
- Compressibility: the Pressure – Volume Response
- Pressure Enhanced Shear Strength – Frictional Materials
- Mohr-Coulomb Failure Criteria
- MAT_SOIL_AND_FOAM (*MAT_005)
Material Characterization - Laboratory Tests & Data
- Hydrostatic Compression Testing
- Tri-Axial Compression Testing
- Other Useful Material Tests
- Case Study – Calibrating the Soil & Foam Constitutive Model (*MAT_005) to Low & High Pressure Soil Data
- Case Study – Quasi-Static Soil Penetration
- MAT_PSUEDO_TENSOR (*MAT_016)
- Simple Input Concrete Models
The following single parameter (unconfined compression strength) models are compared with laboratory data:
- *MAT_PSEUDO_TENSOR (Mode II Concrete) [*MAT_016]
- *MAT_CONCRETE_DAMAGE_REL3 [*MAT_072R3]
- *MAT_WINFRITH_CONCRETE [*MAT_085]
- *MAT_CSCM_CONCRETE [*MAT_159]
- *MAT_RHT [*MAT_272]
- *MAT_CDPM [*MAT_273]
- Case Study – Reinforced Concrete Column Eccentric Loading
- Case Study – Brick Wall Perforation
- Case Study – Concrete Target Perforation using Lagrange with Erosion, Eulerian, & SPH Formulations
- Case Study – Reinforced Concrete Slab under Blast Loading – Blind Blast Simulation Contest
- Modeling Reinforcement – Including Pre and Post-Tensioning
- Winfrith Concrete Model – Crack Patterns
- Strain Rate Effects – Much Ado About Nothing?
- Introduction to the LS-DYNA Cap-Models – Calibrating the Geological Cap Model (*MAT_025)