Guide to Doubly Reinforced RCC Beam Design





RCC Beams

RCC beams are cast in cement concrete reinforced with steel bars. Beams take up compressive and add rigidity to the structure.

Beams generally carry vertical gravitational forces but can also be used to carry horizontal loads (i.e., loads due to an earthquake or wind). The loads carried by a beam are transferred to columns, walls, or girders, which then transfer the force to adjacent structural compression members. In Light frame construction the joists rest on the beam.

Doubly Reinforced Beam

Doubly Reinforced Beam

In this article, we are going to discuss types of beam construction and RCC design of Doubly reinforced beam…

RCC beam construction is of two types:

  • Singly reinforced beam
  • Doubly reinforced beam

Singly reinforced beam

A singly reinforced beam is a beam provided with longitudinal reinforcement in the tension zone only.

Doubly reinforced beam

  • Beams reinforced with steel in compression and tension zones are called doubly reinforced beams. This type of beam will be found necessary when due to head room consideration or architectural consideration the depth of the beam is restricted.
  • The beam with its limited depth, if reinforced on the tension side only, may not have enough moment of resistance, to resist the bending moment.
  • By increasing the quantity of steel in the tension zone, the moment of resistance cannot be increased indefinitely. Usually, the moment of resistance can be increased by not more than 25% over the balanced moment of resistance, by making the beam over-reinforced on the tension side.
  • Hence, inorder to further increase the moment of resistance of a beam section of unlimited dimensions, a doubly reinforced beam is provided.

Besides, this doubly reinforced beam is also used in the following circumstances:

  • The external live loads may alternate i.e. may occur on either face of the member.

For example:

  • A pile may be lifted in such a manner that the tension and compression zones may alternate.
  • The loading may be eccentric and the eccentricity of the load may change from one side of the axis to another side.
  • The member may be subjected to a shock or impact or accidental lateral thrust.

Design procedure for doubly reinforced beam

Step 1

Determine the limiting moment of resistance for the given c/s(Mulim) using the equation for singly reinforced beam

Mulim = 0.87.fy.Ast1.d [1 – 0.42Xumax]

Or

Balanced section

Ast1 = (0.36.fck.b.Xumax)/(0.87fy)

Step 2

If factored moment Mu > Mulim, then doubly reinforced beam is required to be designed for additional moment.

Mu – Mulim = fsc.Asc (d – d’)              [fsc value from page no. 70]

Step 3

Additional area of tension steel Ast2

Ast2 =Asc.fsc/0.87fy

Step 4

Total tension steel Ast, Ast = Ast1 + Ast2

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  1. #1 by seetharaman on July 4, 2010 - 12:02 am

    If the stress in steel in the compression zone is less than yield value, SP 16 gives a table relating strain and stresses. Is there an expression relating that strain and the corresponding stresses? Surely the values have been obtained from the accompanying graph in SP 16. From an examination point of view, how to get that table by calculation?

  2. #2 by G.JAGAN on July 6, 2010 - 8:47 pm

    its good

  3. #3 by Bhabani sankar nahak on October 3, 2010 - 6:38 am

    i need all civil engineering projects so it is best web site civil engineer.

  4. #4 by Ashok on October 12, 2010 - 1:12 pm

    Is this design based on ACI 318-05 code?

    • #5 by BenzuJK on October 13, 2010 - 11:29 am

      Hello,
      I am not very familiar with ACI 318-05 code. This design theory is based on Indian Standard code (IS-456-2000). But the IS code has been updated as per the standards that are recommended in the ACI 318-05 code.

  5. #7 by ravindra kumar goyal on October 27, 2010 - 6:56 am

    this is the best website for all civil engineers

    • #8 by Ram on February 28, 2012 - 1:42 am

      Hello,
      I am not very familiar with ACI 318-05 code. This design theory is based on Indian Standard code (IS-456-2000). But the IS code has been updated as per the standards that are recommended in the ACI 318-05 code.

  6. #9 by ravisankar on December 2, 2010 - 5:41 am

    dear sir/madam,
    can u pls send me ” what are the tips and conditions (limitations) used in the designs of rcc structural elements like beams, columns, slabs, footings etc”. And also the procedure steps as per codal of IS: 456-2000.

  7. #10 by Sudhir on December 12, 2010 - 3:58 am

    It is very usefull to the learned students and teaches too.pl.updadate time to time and give more examples for practice.

  8. #11 by Anandan.S on December 16, 2010 - 3:09 am

    Hi everybody this site is very useful for all civil engineers

  9. #12 by Rahul Rajbhar on December 27, 2010 - 8:29 pm

    i am setisfied this theory because my institute`s teacher also use this theory to explain the all related problems

  10. #13 by Anil kumar gupta on January 6, 2011 - 4:09 am

    dear sir/madam,
    can u pls send me ” what are the tips and conditions (limitations) used in the designs of rcc structural elements like beams, columns, slabs, footings and also give the step by step designing procedure of these elemant with an suitable example as per IS:456-2000”.

  11. #14 by adil on January 25, 2011 - 6:29 am

    dear sir/madam,
    can u pls send me ” what are the tips and conditions (limitations) used in the designs of rcc structural elements like beams, columns, slabs, footings and also give the step by step designing procedure of these elemant with an suitable example as per IS:456-2000”.

  12. #15 by adil on January 25, 2011 - 6:36 am

    please send step by step procedure of rcc design residential building with example and also designing formula sheet.

    • #16 by BenzuJK on February 3, 2011 - 10:21 am

      Addition of formula sheets and more numericals regarding Structural Design will be done in my succeeding articles…

  13. #17 by Amar Pakale on January 31, 2011 - 1:59 am

    please send step by step procedure of rcc design of footing ,column,beam,slab for residential building with example and also designing formula sheet.

  14. #18 by prasad on February 8, 2011 - 1:32 am

    can u help me how to draw the reinforcement details for slab(1 & two way….)

  15. #19 by palaprasanna on February 14, 2011 - 1:44 am

    please seand in civil is codes and rcc footing, column beams slab and rainforcement concret,and structural design and formula sheet

  16. #20 by subramani on February 24, 2011 - 7:51 pm

    sir,we have started a excavation of earth for new construction of house.west facing house.i need help how to design a two way slab for 3 floor residential building.site dimension(w 15′x48′).

  17. #21 by suresh kumar on February 28, 2011 - 6:33 am

    sir, i started new construction. site dimensions are 18′x36′ having east facing. i need the formula for column and beam designing. also need the formula between two column.

  18. #22 by T.S.Janarthanan on March 1, 2011 - 11:52 pm

    what is the limitation in % of steel should be use in doubly reinforced beam sections in compression zone, and max layers of steel
    if any limitation pl guide the value with ref.,

  19. #23 by Rajkumar on March 12, 2011 - 7:55 pm

    Hello everybody,
    Looking for a structural design of multistory building, covered area 450 sq. feet (15′ x 30′).

  20. #24 by yogesh on March 19, 2011 - 10:35 pm

    sir, i started new construction. site dimensions are 18?x36? having east facing. i need the formula for column and beam designing. also need the formula between two column.

  21. #29 by dramachandran on April 26, 2011 - 7:16 pm

    very nicely dealt with re design of doubly reinforced beam…..but steel beam theory also is a mode where steel area in tension zone is equal to that in compression zone …otherwise we have take moment of the areas with respect to NA which may shift up or down depending on over or under reinforced design… am i right ..pl post reply for further knowledge..

    i have more than 40 yrs service since graduation from UNIVERSITY Of MADRAS

  22. #30 by pancham on June 11, 2011 - 2:16 am

    hey i want to know about charectristic strength of hollow concrete any one know plz tell me..?

    • #31 by BenzuJK on June 17, 2011 - 12:00 am

      Hello Pancham,
      The average compressive strength of a hollow concrete block is 5N/mm2.

  23. #32 by Jitendra kumar on June 26, 2011 - 7:42 am

    hey iwant to know about max tensile load on a singly reinforced beam?

  24. #33 by Dhanasekar on September 11, 2011 - 9:52 pm

    Hey,

    I am planning to build my house in which ,I need a column and beam design,which can support the slab spread over about 18 feet,also I like to use only two columns which starts from 1st feet and another in 18th feet,the beams in between this columns has been killing my mind,need help.
    This house will be ground +2 floors.

    • #34 by BenzuJK on July 26, 2013 - 5:46 pm

      Hello Dhanasekar,

      There is some good news I would like to share with you. This will ease your problems with regards to Structural design. Civil Projects Online has officially launched Architectural and Structural Design Services. You can also get an expert advise on the existing structural design of your building.

      Check it out.

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  25. #35 by AYUSH AGARWAL on September 18, 2011 - 11:09 am

    i like the concept………………….its easy to understand……….!!!!!!

  26. #36 by abdullah on September 25, 2011 - 1:47 pm

    u can find almost evey solution in it

  27. #37 by RAJESH on November 6, 2011 - 7:34 am

    please add problems of design of RC beams and slabs as per IS 456:2000. The process of design in detail with diagrams.

    • #38 by BenzuJK on November 12, 2011 - 9:49 am

      Hello Rajesh,
      We will see to it that problems for design of RCC beams are put up on site. Thank you for your feedback.

      Cheers :)

  28. #39 by mohamed azhar on November 21, 2011 - 3:39 am

    thanks, it was nice to revisit the tecnicalities of designs of stucture after long time, being civil engineers we often tend to forget the basics due to the practice which go arround. looking forward for more.

  29. #40 by sam B.tech civil3/4 on December 15, 2011 - 1:01 am

    hi benzulk,
    pls post about the design of shear reinforcement in addition to above desin data…………..

  30. #41 by ws on January 19, 2012 - 6:21 am

    RCEP for RCC structural design and detailing software visit http://www.technobasesoft.com

  31. #42 by Kanza iqbal on January 29, 2012 - 4:02 am

    how to rehabilitate the RCC structure ?

  32. #43 by s kumar on February 1, 2012 - 5:22 am

    Dear sir/madam
    i have single storey house of 200 meter side walls are 9 inches thicks and inner walls are 4 inches. There are no beams and columns of iron bars with cement and artfical beams. i want to construct two more storeys on it and i want to construct beams and columns lthough for that i have to break the walls which will exceed my cost.what should i do without breaking walls i can put beams and columns or i cam construct without these kindly suggest regards

  33. #44 by Tejaswi on February 7, 2012 - 11:20 pm

    hey can u tell me how design a continous beam with load calculations bcz in practical continous beams are to be designed na

    And Please also tell me to calculate breadth & depth for beam ,slab & coloumn

  34. #45 by Sivakumar on February 27, 2012 - 6:09 pm

    Dear Sir/ Madam,

    With reference to the subject “RESIDUAL STRENGTH OF CORROSION DAMAGED CONCRETE STRUCTURES”
    Where can I able to get M30 grade concrete compressive strength test for corrosion damage.
    For example, an experiment which someone might have carried out for a particular type of beam section. The first set of specimens shows results for what is the strength initially (uncorroded). The second set of specimen shows what is its strength after some corrosion. The next set of specimen shows strength for totally depleted concrete cover. The final set specimens show results on section strength based on reduced bar diameter.

  35. #46 by lalit on March 12, 2012 - 12:38 am

    Your site is very helpful for all civil engineers.
    Thank you very much

  36. #47 by Rehan Qamar on March 18, 2012 - 6:16 am

    In Doubly REF. beam, 50% of Shear stress is Taken By stirrups and bent-up…. But Now Curtail bars are provided. By decreasing the Spacing of stirrups at joint (it’s also help in horizontal forces)

  37. #48 by saranraj.m on April 24, 2012 - 12:12 pm

    BenzuJK :
    Hello,
    I am not very familiar with ACI 318-05 code. This design theory is based on Indian Standard code (IS-456-2000). But the IS code has been updated as per the standards that are recommended in the ACI 318-05 code.

  38. #49 by karthik.c on June 26, 2012 - 5:24 am

    for an example T-beam girder (in bridges) is designed by limit state method compare with working stress method is there tension reinforcement will be increase or decrease with reason please

    kind regards,
    karthik.c

  39. #50 by Wai Min on September 18, 2012 - 12:20 pm

    Dear Sir/Madam,
    I want to study detail design calculation of a building with simple drawing.Can you help me from this site or other ways,please.
    with best wishes
    Wai Min

  40. #51 by BRIJ LAL on September 21, 2012 - 3:47 am

    the latest designs of foundations , columns, beams and slabs and other RCC structures are required for better knowledge

  41. #52 by khurshid on September 21, 2012 - 4:10 am

    sir,i want to some question that when we done the select the singly reinforced beam than we make the four steel bar and on these beam provided the compression zone and the tension zone .sir please tell me that when very load come on the load than it will be felldown.

  42. #53 by khurshid on September 21, 2012 - 4:11 am

    ws :
    RCEP for RCC structural design and detailing software visit http://www.technobasesoft.com

  43. #54 by Harish Goyal on October 6, 2012 - 10:35 am

    Actually i want to know about 30′ ( clear span ) beam supported by 15” x 15” column having 1.2% of steel for black cotton soil
    please design this beam for a Hotel building with two way slab
    for short span 14’6” ( clear ) and 15’6” long span . I know about this type of design but this time due to confusion please guide me.

  44. #55 by shubham on October 12, 2012 - 10:26 am

    30 ft’ long balcony roof is standing on two rcc pillars on 10 ft’ from both left and right side at the corner in the left side there is brick wall of 9 inch and 4 ft wide and at right corner brick pillar of 9 inch i want to remove one rcc pillar from right side to increase the parking space no load on roof and pillars are supporting only roof some one suggest me for GADER but it will decrease the height of roof from the floor plz suggest best way to remove the pillar with minimum height decrease

  45. #56 by Hamid Sajjad on October 25, 2012 - 10:32 pm

    Thanks for giving information about Rcc Beam design..

  46. #57 by Rab Nawaz on November 9, 2012 - 5:32 am

    that is awesome n highly informative

  47. #58 by Rab Nawaz on November 9, 2012 - 5:39 am

    can u plz tell me what types of load act on beam & column while designing them and how v can calculate them?

  48. #59 by Sandip khadke on February 2, 2013 - 5:07 am

    Best web for civil engineers

  49. #60 by Dilip Deshpande on May 18, 2013 - 8:24 pm

    I want to calculate the quantity of beam,cloumn,slab,&staircase
    please sen the statement how to calculate the same & thump rule the same
    Thanking you,

    Y.F.
    DDDeshpande

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