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Design of Concrete Structure I

Dr. Ali Tayeh First Semester 2009. Design of Concrete Structure I. Lecture 8. DESIGN OF T-Section BEAMS FOR MOMENTS. Analysis of Flanged Section. Floor systems with slabs and beams are placed in monolithic pour.

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Design of Concrete Structure I

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  1. Dr. Ali Tayeh First Semester 2009 Design of Concrete Structure I

  2. Lecture 8 DESIGN OF T-Section BEAMS FOR MOMENTS

  3. Analysis of Flanged Section • Floor systems with slabs and beams are placed in monolithic pour. • Slab acts as a top flange to the beam; T-beams, and Inverted L(Spandrel) Beams.

  4. Analysis of Flanged Sections Positive and Negative Moment Regions in a T-beam

  5. Analysis of Flanged Sections If the neutral axis falls within the slab depth analyze the beam as a rectangular beam, otherwise as a T-beam.

  6. Analysis of Flanged Sections Effective Flange Width Portions near the webs are more highly stressed than areas away from the web.

  7. Analysis of Flanged Sections Effective width (beff) beff is width that is stressed uniformly to give the same compression force actually developed in compression zone of width b(actual)

  8. ACI Code Provisions for Estimating beff From ACI 318, Section 8.10.2 T Beam Flange:

  9. ACI Code Provisions for Estimating beff From ACI 318, Section 8.10.3 Inverted L Shape Flange

  10. ACI Code Provisions for Estimating beff From ACI 318, Section 8.10 Isolated T-Beams

  11. Various Possible Geometries of T-Beams Single Tee Twin Tee Box

  12. Analysis of T-Beam Case 1: Equilibrium

  13. Analysis of T-Beam Case 1: Confirm

  14. Analysis of T-Beam Case 1: Calculate Mn

  15. Analysis of T-Beam Case 2:Assume steel yields

  16. Analysis of T-Beam Case 2:Equilibrium Assume steel yields The flanges are considered to be equivalent compression steel.

  17. Analysis of T-Beam Case 2: Confirm

  18. Analysis of T-Beam Case 2: Calculate nominal moments

  19. Analysis of T-Beams The definition of Mn1 and Mn2 for the T-Beam are given as:

  20. Limitations on Reinforcement for Flange Beams • Lower Limits • Positive Reinforcement

  21. Limitations on Reinforcement for Flange Beams • Lower Limits • For negative reinforcement and T sections with flanges in tension

  22. Example - T-Beam Find Mn and Mu for T-Beam. hf = 15 cm d = 40cm As = 50cm2 fy= 420Mpa fc= 25Mpa bw= 30cm L = 5.5m S=2.15m

  23. Example of T-Beam Confirm beff

  24. Compute the equivalent c value and check the strain in the steel, es Assume a<t. Steel will yield in the tension zone.

  25. Compute the reinforcement r and check to make sure it is greater than rmin Section works for minimum reinforcement.

  26. Compute nominal moment components

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