Modelling of 25 storey building with the specified properties using ETABS

Answer

Open Etabs and select new model from the File menu

Input the following settings:

Selecting the grid parameters as below:

Selecting the storey parameters as below:

From base storey to Storey 11

From storey 12 to Storey 25

Defining material properties:

1. Concrete - M30 grade

2. Steel

Defining sectional properties:

1. Beam of size 300X400 mm

2. Column of size 800 x 800

3. Slab 150 mm thickness

Entering the load cases as below:

Assigning the seismic load paramaters as below: Seismic zone-III, soil type: II

Assigning the column as below:

Assigning the beams as below:

Assigning the slabs as below (except plinth beam level at 1.5m above base):

Assigning the pin joints to the base of Columns:

Assigning the load of 1.5 kn/m2 live load for roof alone:

Assigning the load of 3 kn/m2 live load for slabs other than roof:

Assigning the frame load of 10 kn/m dead load for all beams:

Defining mass source and assigning the mass source as below:

Assigning the Diaphragm property to all slabs:

Assigning the load combinations as below:

Checking the model for any missing link, overalpping elements

After using Run Analysis command:

After the analysis, natural period of vibration is obtained as below:

From the table, we can observe that Tx1= 4.412 Sec, Ty1= 4.218 sec.

From the table, we can observe natural period corresponding to the torsional mode of oscillation as Txy3= 3.308 Sec is less than two fundamental translational modes of oscillation.

Modal participating mass ratios:

1. From the above table, we can observe that first mode of vibration itself is contributing 80% of mass participation. Hence this condition is satisfied.

2. From the above table, we can observe that first mode of vibration is 4.412 sec. As per the clause,second mode of vibration should differ by atleast 10%. From table, second mode of vibration is 4.218 Sec which is doesn't differ by atleast 10%. Hence this condition is not satisfied.

From the intersotry drift as below, it can be observed that maximum inter story drift is 0.000737 times which is less than codal proivsion of 0.004.