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Continuum finite element modeling of concrete structural components

Continuum finite element modeling of concrete structural components. - Nilanjan Mitra. Crack modeling for concrete. Enriched continua. Discrete crack model. Smeared crack model. Cosserat continua (Cosserat, Green, Rivlin, Mindlin, Vardoulakis, Muhlhaus, de Borst, Willam, Sluys, Etse).

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Continuum finite element modeling of concrete structural components

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  1. Continuum finite element modeling of concrete structural components - Nilanjan Mitra

  2. Crack modeling for concrete Enriched continua Discrete crack model Smeared crack model Cosserat continua (Cosserat, Green, Rivlin, Mindlin, Vardoulakis, Muhlhaus, de Borst, Willam, Sluys, Etse) Empirical global (Vecchio & Collins, Hsu) Advanced remeshing (Ingraffea & Saouma, Cervenka) • Phenomenological • (Rots, de Borst, Willam, • Crisfield, Blaauwendraad) • Fixed crack • Coaxial rotating • Multi-directional fixed Adaptive boundary/fem (Carter, Spievak) Higher order gradient (Aifantis, Vardoulakis, de Borst, Pamin, Voyiadjis) • Advanced fem • Meshfree fem • (Belytschko) • X fem • (Sukumar, Moes, Dolbow) • Embedded discontinuity • (Jirasek, Lotfi, Shing, • Spencer, Belytschko, Sluys, • Larsson, Simo, Oliver, • Armero, Olofsson) • KOS • SOS • SKON Damage Plasticity (de Borst, Simo, Lubliner, Desai, Fenves, Govindjee) Lattice methods (van Mier, Bolander) Microplane models (Bazant, Prat, Ozbolt, Caner)

  3. Models done with TNO DIANA

  4. Constitutive models for continuum FEM • Compressive model for concrete: • Yield surface – Drucker-Prager • Flow rule -- Associative • Compression Hardening/Softening function -- calibrated to match Popovics relation • Plastic strain is zero till 30% of the strength is achieved • Suitable for biaxial loading -- 16% increase in strength • Tensile model for concrete: • Linear tension cut-off • Hordijk model for tension softening • Model for reinforcement steel: • Associated Von-Mises plasticity with strain hardening • Model for bond in between reinforcement and concrete: • Elastic radial response • Transverse response is calibrated to match the Eligehausen model for bond

  5. Benchmark analysis using DIANA Fracture energy tests at UW: Deflected shape Cracks Martin, J., Stanton, J., Mitra, N., and Lowes, L. N.(2007), ACI Materials Journal,104, 575-584

  6. Parametric study for fracture energy test Variation with ft Variation with Ec

  7. Parametric study for fracture energy test Variation with Gf Variation with shear retention, Different crack models

  8. Parametric study for fracture energy test Q4 (2*2) Q8 (2*2) Q8 (3*3) Different element types Variation with threshold angle

  9. Benchmark analysis using DIANA Beam flexure tests: With bond-slip Without bond-slip  Perfect bond Without bond-slip  Perfect bond

  10. Benchmark analysis using DIANA Bond tests: Anchorage mechanism bond test Flexural bending mechanism bond test

  11. Joint region Joint Analysis Crack development Compressive Stress distribution within the joint Top reinforcement bar steel stress • Four noded quad elements for concrete • Drucker Prager associated plasticity for compression • Phenomenological Multi-directional fixed crack model for tension • Linear tension cut-off & Hordijk tension softening curve • Truss element for reinforcement steel in the connection region • Von-mises plasticity for reinforcement steel • Interface elements to model bond – Radial response : Elastic • Transverse response: Nonlinear calibrated to Eligehausen uniaxial bond model • Elastic elements with cracked stiffness to model the beams and columns Model Highlights

  12. Studies carried out with ABAQUS

  13. Model material properties • Compression stress-strain curve : Popovics equation[1973]. • Tension behavior : Mitra[2008]. • Linear response : 30% of maximum compressive strength. • Concrete model: Concrete Damage Plasticity.

  14. Beam-column Joint Model Constant axial load Monotonic increasing lateral load Connection region Beam and column as line element Simulated Joint with loading and boundary condition. Transfer of force/moment to joint : ‘Distributing coupling’ .

  15. Beam-column Joint Model Cont. Column as line element Reinforcements (24/12ɸ for column and 16/12ɸ for beam) Joint region Beam as line element

  16. Beam-column Joint Model Cont. • Studies made up to 2% drift. • Nature of loading :

  17. Behavior of the Beam-Column Joint Under Lateral Loading Cont. Bending stress at 2% drift Shear stress concentration at joint face

  18. Behavior of the Beam-Column Joint Under Lateral Loading Cont.

  19. More work pending for 3d continuum simulation for joints: Looking for students to complete the work Any interested student with some prior expertise in FE modeling, preferably with concrete modeling can contact me in my email add.

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