Challenge

Reinforcement detailing of Columns from ETABS output

DDurga Pavani Pamu4 Mar 2023

ETABS

Note:

Load Combination 68 to Load combination 79 has 0.9Dead +0.9 Brickwall + 0.9 floor finish

Load Combination 73,75,77,79 has positive axial load at the bottom for the column 3F.

Therefore Column 3F is subjected to Tension for the above load combinations.

Question:

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.

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:

The Maximum Asc for the column 3A to be considered as per the ETABS design is;

The highest of the Longitudinal reinforcement of the column from the Base to Terrace;

That is the highest of 7027,6926,4800,4213,3525 = 7027mm2 is Provided for the Column.

The reinforcement detailing for the Column is shown below:

Total no of longitudinal bars = (Total Asc of column)/(Asc of the any dia bar per meter)

Provide 12 bars of 28 mm diameter for the column =615.752*12 =7389mm2 >7027mm2

Hence ok.

The Maximum Asc for the column 3B to be considered as per the ETABS design is;

The highest of the Longitudinal reinforcement of the column from the Base to Terrace;

That is the highest of 4218,4942,5046,4858,4902 = 5046mm2 is Provided for the Column.

The reinforcement detailing for the Column is shown below:

Total no of longitudinal bars = (Total Asc of column)/(Asc of the any dia bar per meter)

Provide 8 bars of 25 mm diameter for the column = 490.87*8 = 3927mm2 and

Provide 4 bars of 20 mm diameter for the column = 314.16*4 = 1256.64mm2

Total =3927 + 1257 =5180 mm2 > 5046 mm2

Hence ok.

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

Shear Reinforcement details from ETABS is obtained as:

Reinforcement detailing of columns in Etabs 2018.

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:- To desig the given column reiforcement by using ETABS software

Procedure:-

Run nanalysis for the given model
Click on concrete frame design and find out the longitudinal reinforcement area and take the screenshot of it.
again select the concrete frame design and go to display design info a nd find the shear reinforcement area and take the screen shot of it.
Select tyhe story edit details to plot the reinforcement details

Special confining reinforcement from IS:13920-2016 (clause 8.1)

1) Lo not less than

a) longer column design = 650mm

2) Confinement spacing not more than 100mm

3) The amount of confinemeent rebar

Ash = maximum of [0.18 Sv h fck/fy(Ag/Ac - 1) ] [0.05 Sv h fck/fy] = 169mm^2