Reinforcement detailing of Columns from ETABS output

REINFORCEMENT DETAILING OF COLUMNS FROM ETABS OUTPUT.

INTRODUCTION:-

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

Shear reinforcement design of columns:

Shear reinforcement demand on column 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:

Longitudinal reinforcement on columns:-

• A circular column needs at least six bars.
• Eight bars are required for rectangular columns, four at the corners and four in the middle.
• A minimum of 0.8% of the gross cross sectional area of a column must be the longitudinal steel's c/s area, according to IS456-2000, the design code for RCC structures.
• Bars must have a minimum diameter of 12 mm.

AIM:-

Reinforcement detailing of columns in Etabs 2018.

The Etabs file for a G+4 building is provided. Run the analysis and design the RCC. Moment resisting frame. The following challenge deals specifiically 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 13920-2016.

PROCEDURE:-

• Access the Challenge 7 attachment that has been sent to us.
• Open the Challenge in the Etabs 20 software after downloading it.

• Select the 3A & 3B columns from all as shown as shown in below:

• Change the view into Elevation view- 3
• And run the analysis

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

• Below showing longidutinal reinforcement of the columns 3A & 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:-

We now need to give the column detailed reinforcement;

1. For grid 3A:-

From base to first floor the maximum Ast = 7027 mm2

So we can provide 8 no's of 32 mm diameter bar=8x803.84

= 6430.72 mm2

also we can provide 2 no's of 20 mm diameter bar= 2x314

= 628 mm2

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

= 7058.72 mm2> 7027 mm2....hence ok

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 Ast= 5046mm2

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

= 3927mm2

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

= 1607.68mm2

Therefore,

Provide 8 bars of 25mm diameter for the column+ Provide 4 bars of 20mm diameter for the column = 3927+1607.68

= 5534 mm2> 5046 mm2.....hence ok

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 low and should not be more than least lateral dimension,(1/6)th of clear span or 450 mm

Result:-

• After the model was verified, the provided Etabs model was examined.
• The necessary reinforcing area was then obtained when concrete frame design was completed.
• Using AutoCAD software, the longitudinal reinforcement features that were derived from the findings were drafted.
• The shear reinforcement details have also been drafted in a similar manner.