Reinforcement detailing of Columns from ETABS output

    Aim: 

    To design the RCC moment resisting frame, to run the analysis of the given ETABS file and to provide details of longitudinal reinforcement for the two columns (3A and 3B) from foundation to the terrace level.

    Introduction:

    The reinforcement detailing of columns consists of carrying out the design of two columns, 3A & 3B for longitudinal and shear reinforcement.

     Shear reinforcement design of columns:

• Shear reinforcement demand on columns is considered as the larger value of,
  • factored shear force demand as per linear structural analysis, and
  • factored equilibrium shear force demand when plastic hinges are formed at ends of the beams given by:

               

• Longitudinal reinforcement on columns is considered as per the below statements:
  • Circular column should have minimum of 6 bars
  • Rectangular columns must have minimum of 8 bars (4 at corners and 4 at mid length)
  • As per IS456-2000, the minimum c/s area of longitudinal steel is 0.8%  of gross cross sectional area of column.
  • These bars should not be less than 12mm in diameter.

    Procedure:

• Open ETABS and then open the given ETABS file.
• Carry out the analysis of the model after checking the model.
• Once analysis is complete, carryout the design of the model.
• For this go to concrete frame design in the tabs provided at the top.
• Select concrete frame design and then select the Design preferences.

                  

• Select Design combinations from the Concrete frame design tab.

                    

• Select Start design check
• Select Display design info and then longitudinal reinforcement.

                  

• Click on concrete frame design then click Display design info and then choose shear reinforcement.

                  

• Now,draft the column reinforcement details on AutoCAD.
• The reinforcement details for the column 3A are given as:
  • Maximum longitudinal reinforcement required is 7027 `mm^2`.
  • Hence, provide 8 no.s of 32mm dia bars and 2 no.s of 20mm dia bars which together contributes an Ast of 7060 `mm^2`.
  • For shear reinforcement, the maximum reinforcement area required is 720 `mm^2`
  • Hence, provide 10mm dia bars @ 150mm c/c at zone A and a spacing of 100 mm  c/c at zone B ( at splicing location and near the beams) which contributes to an Ast of 1570 `mm^2` and 2355 `mm^2` respectively.

                       

                      

• The reinforcement details for the column 3B are given as:
  • Maximum longitudinal reinforcement required is 5046 `mm^2`.
  • Hence, provide 4 no.s of 32mm dia bars and 6 no.s of 20mm dia bars which together contributes an Ast of 5100 `mm^2`
  • For shear reinforcement, the maximum reinforcement area required is 720 `mm^2`.
  • Hence, provide 10mm dia bars @ 150mm c/c at zone A and a spacing of 100mm  c/c at zone B ( at splicing location and near the beams), which contributes to an Ast of 1570 `mm^2` and 2355 `mm^2` respectively.

                  

                  

    Result:

• The given ETABS model has been checked and analysed.
• Concrete frame design has also been carried out and the reinforcement area required has been obtained from it.
• The longitudinal reinforcement details obtained from the results have been drafted in AutoCAD software.
• Similarly the shear reinforcement details also have been obtained.