Reinforcement detailing of Columns from ETABS output

Reinforcement detailing of columns in Etabs 2018.

QUESTION:

The ETABS file for a G+4 building is provided. Run the analysis and design the RCC Moment Resisting Frame. The following challenge deals specifically with two columns at the following grid intersections.

1. 3A
2. 3B

• Provide details of longitudinal reinforcement for the two columns, from foundation to terrace level. Sketch the column cross sectional & elevation details or draft it using autocad software. 
• Show shear reinforcement & lapping details as per special confining reinforcement provision of clause 8.1 of IS 13920 - 2016. 

ANSWER:

 AIM:- 

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

INTRODUCTION:- 

• A reinforced concrete column is a structural member designed to carry compressive loads, composed of concrete with an embedded steel frame to provide reinforcement.
• For design purposes, the columns are separated into two categories: short columns and slender columns.
• A short column is a structural member whose relatively short length virtually ensures it will fail in compression if it is evenly loaded along its axis.
• Columns can be classified as short, intermediate, or long, depending on their lengths, their material properties, and the lengths of other columns in the same structure.
• A slender column is a thin column. For any construction, foundation starts with marking the position of columns and then their design and analysis.
• Slender column can be tested in laboratory to observe the action of buckling or cripping. For a column,based on slenderness ratio, it is termed as long or short column.
• The reinforcement detailing of columns consist 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 larger 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:

            

• Show shear reinforcement & lapping details as per special confining reinforcement provision of clause 8.1 of IS 13920 - 2016. 

Longitudinal reinforcement on columns:-

• Circular column should have a minimum of 6 bars
• Rectangular columns must have a minimum of 8 bars (4 at corners and 4 at mid length)
• As per IS456-2000(design code for RCC structures), the minimum c/s area of lomgitudinal steel is 0.8%  of gross cross sectional area of column.
• Bars should not be less than 12mm in diameter.

PROCEDURE:-

• Open the challange 7 attachment which are provided to us 
• After downloading open the Challenge open it in the Etabs 20 software 

• Select the 3A and 3B columns  from all stories as shown a in below;

• Change the view into  3d view
• And Run the Analysis 

• The analysing are completed to check the left bottom coroner for maximum and minimum displacement.
• Change the view into elvation 3A

• Now we have to start the column design by selecting the "concrete frame design" an below showing;

• Below showing longitudinal reinforcement of the columns 3A and 3B after run the analysis 

• Now we are separately showing longitudinal reinforcement and shear reinforcement of the columns 

Longitudinal reinforcement and shear reinforcement  and Diagramatical details of the column at grid 3A from ETABS;

1. Longitudinal reinforcement:-

2. Shear reinforcement:-

NOW WE HAVE TO PROVIDE DEATIL REINFORCE,MENT TO THE COLUMN;

 1. For GRID  3A -

 From Base to first  floor the maximum`A_(st)`is = 7027 `mm^2`

 So we can provide 8 no's of 32 mm diameter bar = 8 x 803.84

                                                                        = 6430.72 `mm^2`

 also we can provide 2 no's of 20 mm diameter bar = 2 * 314

                                                                             = 628 `mm^2`

 8 no's of 32 mm+2 no's of 20 mm = 6430.72+628

                                                        =7058.72 `mm^2`>7027 `mm^2` ........hence okay

 Diagramatical Details of column at grid 3A are shown below - 

 

 

Longitudinal reinforcement and shear reinforcement and Diagramatical details of the column at grid 3B from ETABS;

1. Longitudinal reinforcement:-

2. Shear reinforcement:-

 

2) For GRID  3B -

 From Base to Terrace floor the maximum `A_(st)`   = 5046 `mm^2`

 So , Provide 8 bars of 25 mm diameter for the column  = 8 x 490.87*8

                                                                                            = 3927`mm^2`

 Provide 2 bars of 32 mm diameter for the column          = 4 x 314.16

                                                                                            = 1607.68`mm^2`

Therefore; 

Provide 8 bars of 25 mm diameter for the column + Provide 4 bars of 20 mm diameter for the column   =

               = 3927 + 1607.68

               = 5534 `mm^2`>5046 ...........hence okay

Diagramatical Details of 3B Grid are shown below ;

Now ,Typical Beam column Joint as per special confining reinforcement provision of clause 8.1 of IS 13920 -2016 

As per IS 13920 - 2016 at beam column junction:-

• For beam - The spacing from the face of the beam should not be more than 100 mm till 2d 
• For Column - The spacing from the face of the column will be lo and should not be more than Least lateral dimension,`(1/6)^(th)` of clear span or 450 mm 

 RESULT:-

• The given Etabs model has been analysed after checking the model.
• Then concrete frame design has also been carried out hence the reinforcement area required has been obtained.
• The longitudinal reinforcement details obtained from the results have been drafted in AutoCAD software.
• Similarly the shear reinforcement detiakls also have been drafted.