Design of RCC Rectangular Beams as per IS 456-2000

1. GENERAL :
The design of reinforcement for Limit State of Collapse in Flexure and Shear for Rectangular Beam Section is carried out as per IS-456. Check for Minimum and Maximum Reinforcement criteria is considered for Flexure as per the Code. Check for minimum shear reinforcement, maximum spacing of shear reinforcement is done as per the Code.

2. Rectangular Beam Design for Flexure as per IS 456 :
* The Input data for the Beam design for Flexure :
  Factored BM (Mu), Beam Dimensions and Effective Cover for Tension and Compression Steel, Grade of Concrete fck
* Clear cover for the beam would be as per Table16 for Durability criteria and as per Table 16A for Fire resistance criteria. In mild exposure condition for a fire resistance of 0.5 hour, 20mm cover is provided for stirrups. Based on this eff. cover would be calculated by designer based on no. of layers in which steel would be provided. To start with 40 to 50mm cover may adopted and corrected on finding the actual disposition of bars in next iteration by the designer.
 * For given BM, Mu < Mu,lim, the section is singly reinforced beam and only Tension steel is calculated, comp. steel would be zero. Minimum area of tension steel Ast,min (mm2)  = 0.205 % of the gross area of section.  If Ast, calculated < Ast,min, Ast,min is reported. For Mu > Mu,lim both tension and comp. steel are calculated. The Maximimum Tension Steel is 4 % of the gross area of section. If Ast,calculated  > Ast,max, A message to "REV DEPTH" appers in the cell.
* Based on the area of steel required 'Ast', use Rebar calculator to to determine size and number of bars required. Recalculate the effective cover based on the rebar arrangement, with input of revised cover recalculate design steel required. The spacing < 180mm as per Cl.26.3.3. for zero % redistribution of moment with Fe 415 steel.  

3a.  Rectangular Beam Design for Shear  as per IS 456 :
* The Input data for the Beam design for Shear :
  Factored Shear Force at Critical Section (Vu), Effective Cover for Tension Steel, Grade of Steel for Strrups, No. of Legs and dia. Of Strrups
* The spacing of stirrups would be calculated using Cl. 40.4, along with minimum shear reinforcement and max. spacing criteria as per Cl. 26.5.1.6. The designer should see thatclosest spacing should be approximately 100mm for ease of concreting, as far as possible.

3b. Design Shear Force for Minimum Shear Reinforcement:
* It will calculate the magnitude of factored shear force which will be safely carried by minimum shear reinforcement. Hence the segment of beam can be identified by the designer from the Shear Force envelope obtained from the analysis results, for which minimum shear reinforcement would suffice.
* The Input data for the Beam design for Shear :
* The Input data : Area of Tension Steel at Critical Section, Effective Cover for Tension Steel, Grade of Steel for Strrups, No. of Legs and dia. Of Strrups

4. DESIGN PROCESS :
Give Input Data in white space, with red font. See the Instructions on the BM-DSN worksheet.
 
5. DISCLAIMER
* TO BE USED BY QUALIFIED STRUCTURAL ENGINEER FOR DESIGN AS PER OF IS -  456. CHECK BEFORE USE.
* NO LIABILITY OF DEVELOPER OF ANY TYPE UNTILL A LICENCE AGREEMENT IS SIGNED BETWEEN USER AND DEVELOPER, AND THAT THE USER IS FORMALLY TRAINED FOR USE OF THIS SPREAD SHEET,  INCL. ITS ADVANTAGES AND ITS LIMITATIONS.

Indian Standard 456

RCC Design