Test before Final ( T Beam )

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Test before Final ( T Beam )

  1. 1. ULTIMATE STRENGTH DESIGN T BEAM DESIGN : Singly and Doubly Presented By S. M. Rahat Rahman 10.01.03.044
  2. 2. A singly reinforced beam is one in which the concrete element is only reinforced near the tensile face and the reinforcement, called tension steel, is designed to resist the tension.
  3. 3. A doubly reinforced beam is one in which besides the tensile reinforcement the concrete element is also reinforced near the compressive face to help the concrete resist compression. The latter reinforcement is called compression steel. When the compression zone of a concrete is inadequate to resist the compressive moment (positive moment), extra reinforcement has to be provided if the architect limits the dimensions of the section.
  4. 4. For monolithically casted slabs, a part of a slab act as a part of beam to resist longitudinal compressive force in the moment zone and form a TSection.
  5. 5. From ACI 318, Section 8.10.2 Effective Flange Width : Condition 1 For symmetrical T-Beam or having slab on both sides a) 16 hf + bw b) Span/4 c) c/c distance (smallest value should be taken)
  6. 6. From ACI 318, Section 8.10.2 Effective Flange Width : Condition 2 Beams having slabs on one side only a) bw + span/12 b) bw + 6hf c) bw + 1/2 * beam clear distance (smallest value should be taken)
  7. 7. From ACI 318, Section 8.10.2 Effective Flange Width : Condition 3 Isolated T Beam a) beff ≤ 4 bw b) hf ≥ bw/2 (smallest value should be taken)
  8. 8. T- versus Rectangular Sections When T-shaped sections are subjected to negative bending moments, the flange is located in the tension zone. Since concrete strength in tension is usually neglected in strength design, the sections are treated as rectangular sections of width w b . On the other hand, when sections are subjected to positive bending moments, the flange is located in the compression zone and the section is treated as a T-section shown in Figure 1
  9. 9. Strength Analysis : 1st case : (N.A. is with in the flange) Analyze as a rectangular beam of width b = beff Mn = As fy (d − a/2)
  10. 10. Case 2 : (N. A. is with in the web) T beam may be treated as a rectangular if stress block depth a ≤ hf and as a T beam If a > hf .
  11. 11. Analysis of T-Beam Case 1: a Equilibrium hf T C a As f y 0.85fc beff
  12. 12. Analysis of T-Beam Case 1: a hf Confirm s y a c 1 s d c c cu 0.005
  13. 13. Analysis of T-Beam Case 1: a Calculate Mn hf Mn As f y d a 2
  14. 14. Analysis of T-Beam Case 2: a hf Assume steel yields Cf 0.85 f c b bw hf Cw 0.85 f c bw a T As f y
  15. 15. Analysis of T-Beam Case 2: a hf Equilibrium Assume steel yields Asf 0.85 f c b bw hf fy The flanges are considered to be equivalent compression steel. T Cf Cw a As Asf f y 0.85 fcbw
  16. 16. Analysis of T-Beam Case 2: a hf Confirm a hf a c 1 s d c c cu 0.005
  17. 17. Analysis of T-Beam Case 2: a hf Calculate nominal moments Mn M n1 M n2 M n1 M n2 As Asf f y d Asf f y d hf 2 a 2
  18. 18. Analysis of T-Beams The definition of Mn1 and Mn2 for the T-Beam are given as:
  19. 19. Limitations on Reinforcement for Flange Beams • Lower Limits – Positive Reinforcement min As b wd larger of fc 4f y 1.4 fy
  20. 20. Limitations on Reinforcement for Flange Beams • Lower Limits – For negative reinforcement and T sections with flanges in tension fc (min) larger of 2f y 1.4 fy
  21. 21. Thank you

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