Reinforcement detailing of Columns from ETABS output

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 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.

Ans:-

Aim:

• To provide Longitudinal reinforcement detail of two columns (3A and 3B) from foundation to terrace level.
• To provide Details of Transverse Reinforcement under Special Limited Reinforcement in Paragraph 8.1 of IS 13920-2016.

Introduction:

• A reinforced concrete column is a compressive load-bearing structural element composed of concrete with embedded reinforcing steel.
• For design purposes, columns are divided into two categories: short columns and thin columns.
• short column is a structural element whose relatively short length practically guarantees compression failure when a load is applied uniformly along its axis.
• Columns can be classified as short, medium, or long based on length, material properties, and other column lengths of the same design.
• The foundation of any structure begins with the design and analysis after marking the position of the columns.
• Thin columns can be tested in the laboratory to observe warping or the effects of warping.
• Columns based on variable coefficients are called long columns or short columns.

Procedure:

• Download and open the model given in challenge 7 in Etabs.
• Open the elevation view of the model.
• Check the model for errors and run the analysis.
• Start the designing process by selecting the ‘start design/check’ option.
• After the software completes the process the longitudinal reinforcements are visible as shown.
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• Next you need to select Show project information option and then select Shear bar in project output and click OK button.
• Shear bar details are now displayed as shown below.
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• Here, for column 7 (intersection 3A), we use a column size of 450 mm X 650 mm. The maximum value of Ast for column 7 is 7027mm² which now gives 16 rods of 18 mm diameter (16-18Φ) as shown below.
• And provides a clamp size of 10mm, 100mm spacing for Area A and 150mm spacing for Area C as shown below.
• And the Details of transverse reinforcing bars are provided according to IS 13920-2016, Section 8.1, Regulations for special confining reinforcing bars.
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• Here, for column 8 (intersection 3B), we use column size 450 mm X 650 mm. The maximum value of Ast for column-8 is 5046mm²
• which now gives 16 rods of 20 mm diameter (16-20Φ) as shown below.
• and provides a clamp size of 10mm, 100mm spacing for Area A and 150mm spacing for Area C as shown below.
• And Details of transverse reinforcing bars are provided according to IS 13920-2016, Section 8.1, Regulations for special restricted reinforcing bars.
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Result:

• Successfully provided the longitudinal reinforcement details of two columns (3A and 3B) from foundation to terrace height.
• The details of shear reinforcement are given according to IS 13920-2016, clause 8.1 special confining reinforcement which are as follows:
  1. For L₀- not less than
     1. Larger column dimension-650mm
     2. 1/6^th of clear span of column – 560mm
     3. 450mm

So, adopt 650mm.

1. Confinement spacing not more than:
   1. 1/4^th of smaller column dimension- 113mm
   2. 6 times of dia of column main bar- 168mm
   3. 100mm

So, adopt 100mm

• AutoCAD software was also used to provide details of the column's section and height.