presentation on rectangular beam design singly or doubly (wsd)

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welcome to my presentation on rectangular beam design singly or doubly under working stress design

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presentation on rectangular beam design singly or doubly (wsd)

  1. 1. Ahsanullah University of Science and Technology  NAME: RAIHAN MANNAN  STUDENT ID : 10.01.03.101  SEC : B
  2. 2. MY TOPIC NAME RECTANGULAR BEAM DESIGN   Singly Rectangular Beam Doubly Rectangular Beam Under Working-stress Design
  3. 3. Section of Rectangular Beam
  4. 4. Stress distribution in rectangular beam under working load
  5. 5. Singly Rectangular Beam  A Beam is any structural member which resists load mainly by bending. Therefore it is also called flexural member. Beam may be singly reinforced or doubly reinforced. When steel is provided only in tensile zone (i.e. below neutral axis) is called singly reinforced beam.
  6. 6. Assumptions for DesignofMembers by Working Stress Method    Plane sections before bending remain plane after bending. Normally, concrete is not considered for taking the tensile stresses except otherwise specifically permitted. Therefore, all tensile stresses are taken up by reinforcement only. The stress-strain relationship of steel and concrete is a straight line under working loads.
  7. 7. Singly Rectangular Beam stress distribution
  8. 8. Where,  Jd =momnet arm=(1-k/3)  Compressive force , C =(bkd/2)fc  Tensile force , T = Asfs
  9. 9.  neutral axis is determined by equating the moment of the tension area to the moment of the compression area
  10. 10. Moment calculation:  Start by determining
  11. 11. Reinforcement calculation:
  12. 12. Design equation for singly reinforcement beam
  13. 13. Doubly Reinforcement beam  If a beam cross section is limited because of architectural or other considerations, it may happen that the concrete can not develop the compression force required to resist the given bending moment, in this case ,reinforcement is added in the compression zone, resulting in so called Doubly reinforced beam .i.e., one with compression as well as tension reinforcement.
  14. 14. Why Doubly reinforcement used If concrete can not develop the required compressive force to resist the maximum bending moment, then additional reinforcement is provide in the compression zone.  Reinforcement is provided in both compression and tension zone. 
  15. 15. Stress distribution in doubly reinforced beam
  16. 16. Development of moment  In stress distibution,the design moment is more than the balanced moment of resistance of the section, M = M1 + M2 The additional moment M2 is resisted by providing compression reinforcement As’ and additional tensile reinforcement As2
  17. 17. Moment calculation  Moment is obtained by, M1=(fc/2)kjbd^2 = As1fsjd M2=As2fs(d-d’) =As’fs’(d-d’)
  18. 18. Reinforcement in Beam The total tensile reinforcement Ast has two components As1+As2 for M1 and M2  The equation of Ast,  Ast=As1+As2 Where, As1= (bd/100) And As2 = M2/[Ó (d-d’)]  compressive reinforcement,
  19. 19. Clear cover for design Not less than 1.5 in. when there is no exposure to weather or contact with the ground  For exposure to aggressive weather 2 in. 
  20. 20. CLEAR DISTENCE OF REINFORCEMENT  Clear distance between parallel bars in a layer must not be less than the bar diameter or 1 in.
  21. 21. IF YOU HAVE ANY QUESTION THEN YOU CAN ASK ME

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