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European Project Fire Resistance of Innovative and Slender Concrete - PowerPoint PPT Presentation

European Project Fire Resistance of Innovative and Slender Concrete Filled Tubular Composite Columns (FRISCC) Elliptical section members Prof Leroy Gardner Dr Finian McCann FRISCC - Fire Resistance of Innovative and Slender Concrete Filled


  1. European Project Fire Resistance of Innovative and Slender Concrete Filled Tubular Composite Columns (FRISCC) Elliptical section members Prof Leroy Gardner Dr Finian McCann

  2. FRISCC - Fire Resistance of Innovative and Slender Concrete Filled Tubular Composite Columns OUTLINE Elliptical section members 1. S TEEL EHS MEMBERS I NTRODUCTION S TRUCTURAL INVESTIGATIONS D ESIGN RULES 2. C ONCRETE - FILLED EHS MEMBERS I NTRODUCTION T ESTING AND SIMULATIONS D ESIGN GUIDANCE D ESIGN EXAMPLE

  3. S TEEL EHS MEMBERS - INTRODUCTION Steel EHS members: z • Recently introduced as hot-finished products in EN 10210 a • Combine merits of CHS and RHS y • Elegant aesthetics (CHS) a • Differing rigidities about principal axes (RHS) � more suitable for applications in bending b b FRISCC

  4. S TEEL EHS MEMBERS - APPLICATIONS Applications of steel EHS Heathrow Airport, UK Jarrold store, UK FRISCC

  5. S TEEL EHS MEMBERS - APPLICATIONS Applications of steel EHS Society Bridge, Scotland Madrid Airport, Spain FRISCC

  6. S TEEL EHS MEMBERS – STRUCTURAL INVESTIGATIONS Structural scenarios addressed: 1. Local buckling and cross-section classification 2. Shear resistance 3. Combined bending and shear 4. Flexural buckling of columns FRISCC

  7. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification: Elastic critical local buckling – compression and minor axis bending Initial aim was to determine an equivalent CHS diameter D e E t r max σ = cr y 2 r 3 ( 1 ) − ν max b In compression or minor z axis bending, equivalent b diameter is: D e = 2r max =2a 2 /b a a FRISCC

  8. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification: Elastic critical local buckling – major axis bending z Compression a r max Maximum y compression a Buckling initiates Tension D e = 0.8a 2 /b b r max is the maximum local b radius of curvature FRISCC

  9. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification – Testing: Material testing of Geometric Minor axis bending tests Compression tensile coupons measurements tests FRISCC

  10. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification – Finite element modelling: • FE models developed in ABAQUS • Models validated against test results • Full loading history and failure modes well predicted • Parametric studies conducted, varying: • Cross-section slenderness • Aspect ratios (for all tests, a / b = 2) FRISCC

  11. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification – FE validation: 1800 FE Load N (kN) Test 1200 600 0 0 6 12 18 24 End shortening δ (mm) FRISCC

  12. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification: Max. load F u normalised by yield load F y 2.0 EHS CHS FE 1.5 F u / F y 1.0 2a D e = 2r max = 2a 2 /b 0.5 2b ε = (235/f y ) 0.5 Class 1-3 Class 4 0.0 0 30 60 90 120 150 180 210 240 270 D e / t ε 2 FRISCC

  13. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification: Minor axis bending – ultimate moment to elastic moment 2.5 2a D e = 2r max = 2a 2 /b EHS CHS 2.0 2b ε = (235/f y ) 0.5 FE 1.5 M u /M el 1.0 Class 1-3 Class 4 0.5 0.0 0 20 40 60 80 100 120 140 160 180 200 220 240 260 D e /t ε 2 FRISCC

  14. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification – summary of measurements of slenderness: Corresponding point on Loading Equivalent diameter cross-section 2a Axial D e = 2 a 2 / b 2b compression 2a Minor axis D e = 2 a 2 / b bending (z-z) 2b D e = 0.8 a 2 / b a / b > 1.36 2a Major axis 2a bending (y-y) D e = 2 b 2 / a a / b ≤ 1.36 2b 2b FRISCC

  15. S TEEL EHS MEMBERS – CROSS - SECTION CLASSIFICATION Cross-section classification – summary of slenderness limits: Proposed slenderness limits Type of Diameter compression ratio loading Class 1 Class 2 Class 3 Axial 90 ε 2 D e / t Not applicable compression Minor axis D e / t bending (z-y) 50 ε 2 70 ε 2 140 ε 2 Major axis D e / t bending (y-y) FRISCC

  16. S TEEL EHS MEMBERS – S HEAR RESISTANCE Shear resistance: • Three-point bending tests ( a / b = 2): • 12 major axis, 12 minor axis • Varying slenderness and length F L/2 L/2 Moment gradient Uniform shear Uniform shear FRISCC

  17. S TEEL EHS MEMBERS – S HEAR RESISTANCE A f / 3 v y V Design plastic shear resistance: = pl , Rd γ M 0 (A v = shear area, f y = yield strength, γ M0 = 1.0) For shear along y-y: For shear along z-z: z y a b z y b a a a b b A v = (4 b -2 t ) t A v = (4 a -2 t ) t FRISCC

  18. S TEEL EHS MEMBERS – S HEAR RESISTANCE Moment–shear interaction design guidance based on test results: 1.5 Shear along y-y Shear along z-z M u / M pl,Rd or M u / M el,Rd 1.0 0.5 Proposed shear-moment interaction 0.0 0.00 0.25 0.50 0.75 1.00 1.25 V u / V pl,Rd FRISCC

  19. S TEEL EHS MEMBERS – C OLUMN BUCKLING Column buckling: • Column tests performed ( a / b = 2): • 12 major axis, 12 minor axis, varying slenderness and length Load cell Knife edge C L Strain gauge LVDT Hydraulic jack FRISCC

  20. S TEEL EHS MEMBERS – C OLUMN BUCKLING Column buckling – finite element validation: 750 FE Load N (kN) 500 Test 250 0 0 15 30 45 60 Lateral deflection at mid-height ω (mm) FRISCC

  21. S TEEL EHS MEMBERS – C OLUMN BUCKLING 1.5 Buckling about y-y N u /N y or N u /N eff 1.0 Buckling about z-z y z 0.5 EC3 – curve ‘a’ 0.0 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 Member slenderness λ Buckling curve ‘a’ can be used for EHS, as for other hot-finished hollow sections

  22. S TEEL EHS MEMBERS – C OLUMN BUCKLING Design guidance: • Presented proposals are reflected in the Blue book • Also in equivalent US design guidance • Expected to be incorporated in future revisions of EC3

  23. S TEEL EHS MEMBERS – S UMMARY Steel EHS members - conclusions: • New addition to hot-rolled range • Significant testing and FE modelling programmes • Design rules for primary structural configurations • Incorporation into structural design codes ongoing FRISCC

  24. C ONCRETE - FILLED EHS MEMBERS - INTRODUCTION Concrete-filled EHS columns: • Design guidance currently exists for other concrete-filled tubular columns (CHS, SHS, RHS) • No current guidance for emerging CFEHS structural solution • Among aims of FRISCC project: develop guidance on the design of CFEHS columns • At room temperature (Imperial College) • In fire conditions (UP Valencia) FRISCC

  25. C ONCRETE - FILLED EHS MEMBERS - INTRODUCTION Current guidance: • Cross-section classification - Eurocode 4: “composite section classified according to least favourable class of steel elements in compression” (using Eurocode 3 limits) • Resistance of compression members: not available for CFEHS � adopt rules for CHS / RHS? Strategy for development of design guidance: • Experimental programme • Validation of numerical model against experiments • Numerical parametric study • Develop design rules for CFEHS columns and beam-columns based on results FRISCC

  26. C ONCRETE - FILLED EHS MEMBERS - EXPERIMENTS Experimental investigation: • 27 concrete-filled 150×75×6.3 EHS specimens tested in compression • Grade S355 steel, grade C30 concrete • Loading was either concentric or with various major / minor axis eccentricities • Specimens with different global slenderness (lengths) examined • Some specimens with steel reinforcement (4No. T10 bars) FRISCC

  27. C ONCRETE - FILLED EHS MEMBERS - EXPERIMENTS Cross-sectional geometry of experimental specimens: Position of eccentric load e y T10 reinforcing bar b 18 mm a 40 mm 15 mm 10 mm e z Specimen buckling about major Specimen buckling about minor axis axis FRISCC

  28. C ONCRETE - FILLED EHS MEMBERS - EXPERIMENTS Testing of columns: FRISCC

  29. C ONCRETE - FILLED EHS MEMBERS – NUMERICAL MODELLING Numerical modelling: • Finite element model of CFEHS column developed in ABAQUS • Steel material model based on tensile testing of coupons • Concrete damage plasticity model used end-plate steel tube concrete core Buckling axis FRISCC

  30. C ONCRETE - FILLED EHS MEMBERS – NUMERICAL MODELLING Validation of numerical model – ultimate loads: 1400 1200 1000 N u,exp (kN) 800 600 400 Present study +10% 200 Unity -10% 0 0 200 400 600 800 1000 1200 N u,FEA (kN) N u,exp / N u,FEA : average = 1.12, STDEV = 0.07 FRISCC

  31. C ONCRETE - FILLED EHS MEMBERS – NUMERICAL MODELLING Validation of numerical model – load–deflection behaviour: 800 E20:L2-MA-50-R - test E20:L2-MA-50-R - FEA 700 E21:L1-MA-50-R - test E21:L1-MA-50-R - FEA 600 E22:L3-MI-25-R - test E22:L3-MI-25-R - FEA 500 Load (kN) 400 300 200 100 0 0 5 10 15 20 25 Axial displacement (mm) FRISCC

  32. C ONCRETE - FILLED EHS MEMBERS – NUMERICAL MODELLING Validation of numerical model – failure mode: FRISCC

  33. C ONCRETE - FILLED EHS MEMBERS – NUMERICAL MODELLING Numerical parametric study: • 360 specimens modelled, varying • cross-section • slenderness • reinforcement ratio • cover to reinforcement • load eccentricity (also modelled concentric loading) • buckling axis • Results used as basis to formulate design rules FRISCC

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