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COLD BENDING RESEARCH NEEDS

COLD BENDING RESEARCH NEEDS. Courtesy S. Kozel. UNIVERSITY OF BALAMAND RESEARCH COUNCIL JUNE 23 rd , 2004. OUTLINE. MOTIVATION PROPOSED METHOD PREVIOUS WORK CURRENT WORK FUTURE WORK. Cut Curving. Flange. Flange. Flange. Scrap. Fit-Up. Pressure Applied During Fit-up. Web.

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COLD BENDING RESEARCH NEEDS

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  1. COLD BENDING RESEARCH NEEDS Courtesy S. Kozel UNIVERSITY OF BALAMAND RESEARCH COUNCILJUNE 23rd, 2004

  2. OUTLINE • MOTIVATION • PROPOSED METHOD • PREVIOUS WORK • CURRENT WORK • FUTURE WORK

  3. Cut Curving Flange Flange Flange Scrap

  4. Fit-Up Pressure Applied During Fit-up Web Pressure Applied During Fit-up Flange Flange Fitting Jig

  5. Problems ? • - Costly because of excessive waste • - Too much scrap for sharp curvatures • - Used for mild curvatures (R  300m) • - Fit-up operation too complicated

  6. Heat Curving HEATED AREA

  7. Problems ? • - Trial and error process relying on uneven expansion/contraction. • - Takes time to heat and much longer to cool down. • - Results not known till AFTER cooling. • - If it is not right, process must be repeated. • - Ties up shop, slow and costly.

  8. 3-ROLLERS BENDING PINCHING ROLLER Courtesy AISC

  9. Bridges: Current Status ? • Not allowed by AASHTO, concerns: • - Cracking, Fracture • - Flange Upsets • - Dimples • - Web Crippling • No criteria is available • Depends on skill and knowledge of fabricators

  10. MIAMI METROMOVER PROJECT

  11. TAMPA STEEL TAMPA STEEL 1: Hydraulic jack (bot. flange) 2: Hydraulic jack (top flange) 3: Longitudinal arms 4: Steel plate 5: Clamps

  12. PROPOSED CONCEPT L 2 4 5 3 6 1 7 3 5 max = 4 2 6 x

  13. FULL-SCALE DEMO FULL-SALE DEMO

  14. Top Flange Bending S

  15. Bot Flange Bending 5 7 1: Jack 2: Head 3: Plate 4: Angle 5: Support 6: String Line 7: Stiffener 1 4 2 3 6

  16. FORMULATION • PARAMETERS: • - Load Frame Spacing S • - Bending Loads Ptf, Pbf • - Deflection  within span S • - Segment Length Li • - Number of Segments n • - Offsets S Li Ptf

  17. Comp. side Flange S = Lp LOAD FRAME SPACING (S) • Based on lateral bracing limit: • S = 14.4c for Grade 250 steel • S = 12.2c for Grade 345 steel • For unsymmetrical sections use ctf Load P Flange Width 2c

  18. BENDING LOADS (Ptf, Pbf) • From simple beam plastic load analysis: Top Flange: Ptf based on ttf, ctf Bot. Flange: Pbf based on tbf, cbf Constant P Fytfc c Fytfc c Mp = Fytfc2 S

  19. DEFLECTION  ctf cbf Ptf  Pbf Load P tf bf set  = cte = tf    bf ??? bf Plastic Hinge tf Set P = Pbf, Load in cycles m=tf/bf P  Pbf (not in this scope) S

  20. SEGMENT LENGTH Li 2Li tf S [m]   Constant   [m-1] [m+1] 2Li 2Li/S Radius R

  21. Length L nLi a a n n+1 2 4 5 3 1 Line of symmetry NUMBER OF SEGMENTS n Round-down to the nearest even integer adjust

  22. OFFSETS ii, ij 2 6 7 1 3 5 4 Load: 2 22 Load: 3 23 33 Load: 4 24 34 44 Load: 5 25 35 45 55 Load: 6 max 26 46 36 56 66

  23. FABRICATION AIDS (LOADS) Ptf =0.462.5152 = 260kN,Pbf =0.465252 = 1440kN P/tfc2(kN/cm3) G 400 G 345 0.46kN/cm3 G 250 S (cm) 215cm

  24. FABRICATION AIDS (Deformations) tf = 3.5/15 = 0.23cm,bf = 3.5/25 = 0.14cm G 400 G 345 round-up to 2 G 250 c (cm2) 3.5cm2 S (cm) S = 215cm S (m)

  25. FABRICATION AIDS (Multiple Load) G 400 Bot. Flange load /(S2/c)105 G 345 G 250 = (tf – bf)=0.09cm [/(S2/c)]105 = 4.9. 4.9 Px/tfc2/S (kN/cm2) S (m) R/c (cm/cm) 97 Px=975(25)2/215=1400kN (kN/cm2)

  26. FABRICATION AIDS (Segments) G 400 G 345 Li=0.25215=53.75cm n=(1200–215)/53.75= 18.3 Round-down to n=18. Li=(1200–215)/18= 55 cm G 250 Li/S cm/cm) 800 S (m) R/c (cm/cm)

  27. SUMMARY • - Development of a standardized cold curving procedure. • Relationships (loads vs. deformations), Fabrication Aids are now available. • - Limits are set on maximum strains (plastic) • Note: Residual stresses may be released by heat treatment

  28. Sen,R., Gergess,A. & Issa,C. “Finite Element Modeling of Heat-Curved I-Girders” ASCE Journal of Bridge Eng, Vol. 8, No. 3, May/June 2003,pp.153-161. • Gergess A. & Sen R. (2003). “Simplified Heat-Curving Analysis”. Journal of Transportation Research Board, No. 1861, Construction, pp. 101 - 114 • Gergess, A. & Sen, R. “Inelastic Response of Simply Supported I-Girders Subjected to Weak Axis Bending,” Proceedings of the International Conference on Structural Engineering, Mechanics and Computation, Cape Town, South Africa, Edited by A.Zingoni, Vol. I, pp 243-250, 2001. • Gergess, A. and Sen R. “Fabrication Aids for Cold Straightening Structural Steel Girders”. AISC, EngineeringJournal (in press), 2004. • Gergess, A. and Sen R. “Cold Curving Un-symmetric Un-stiffened Steel Girders, Journal of Constructional Steel Research, London, UK (in press), 2004. PUBLICATIONS

  29. Current Work • Theoretical Investigation: 3D Finite Element Modeling

  30. Current Work Strain Hardening Loading Fy max  10 y STRESS Un-Loading y STRAIN residual  8.5y

  31. Current Work • Effects of Cold Bending on Steel mainly fracture characteristics: • Perform Visual • Inspection using • NDT Techniques

  32. AASHTO Requirements

  33. ASSESSMENTS

  34. Acknowledgments • Samuel & Julia Flom Fellowship: USF • Dr. Rajan Sen • Ronald Medlock, Texas DOT “Performance and Effect of Hole Punching and Cold Bending on Steel Bridges”. Research project conducted by University of Texas at Austin and Texas A&M University, 2003. • TRB/AASHTO/NSBA

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