Modelling of 25 storey building with the specified properties using ETABS

Aim:

To Model and Analyze a 25 Multi-Story Building using ETABS and checking those results with respect to the IS 1893-2016 Part-1.

Introduction:

• The Seismic Design for the Building or Structures is given by IS 1893-2016.
• We can select the basis for design in the ETABS software while anayzing the structure.
• We can cross-check the results after the analysis performed on the structure with the specification provided in the IS code 1893-2016.

Procedure:

• Grid Creation:

• Open and create a New project in ETABS.
• Give the code and units which needed to be followed.
• Create the Grid spacing either custom or inbuilt Grid spacing by giving the number of grids in X and Y direction.
• Now enter the storey heights using custom option.
• Rename the storey names as per the requirement.
• Assign the Master storey for the required storey or floors for easy modelling and load assigning.
• After creating the grids and storey definitions a skeleton structure is developed both Plan and 3D view.

• Modelling:

• We need to create the Material Properties.
• For concrete create M30 and for Steel reinforcement create Fe-415.
• Now we need to create the Section Properties for Beams, Columns and Slabs.
• Go to Define Tab > Section Properties > Frame Sections > Add new property > Select the material from the material property already created.
• Add the reinforcement details for the Column and Beams respectively.
• The same procedure is followed for the Columns also.
• For Slab - Select the Model Property as Membrane because we dont want the slab element to act as a Flange section by taking the Shear Force.
• After creating the Sections we need to model them into the structure.
• Select Quick Draw Column option and provide columns at every grid intersection.
• Check whether the option is selected to all floors.
• Now comes the Beam modelling, click on Quick Draw Beam and select All floors option.
• Select the required data type and select the grid lines where we need to model the beam.
• Now for slabs we do not want to model it in Plinth.
• Therefore go the First storey and select similar storey option.
• Model the slabs as per the requirement by selecting Quick Draw Slab.
• Now for assigning the supports go the Base floor and select the grid points.
• Go to Assign > Joints > Restrain > Se;ect the required support condition.

• Assigning the Loads:

• Go the Define > Load Patterns.
• We need to add new load properties such as Seismic, Live and Wall loads.
• Give the load combinations to the loads assigned.

• Analysis Commands:

• For the Seismic Analysis we need to assign the Diaphragm command.
• Select all the Slabs > Assign > Shell > Diaphragm > Apply.
• A Centre of Mass is created.
• Now firstly check the model for any overlapping or errors.
• Now run analysis.

• Checking the Results:

• After the Analysis is completed.
• Go to the Model Explorer > Tables > Analysis Results > Model Information.
• We need to check the Modal Time Period and Modal Participation Factor.

Result:

The structure has been Modeled and Analysed and the required results are displayed below.

Criteria		Desirable Solution	Exercise Result
Fundamental Translational Natural Period	X-Direction	4.4 sec	4.41
	Y-Direction	4.2 sec	4.22
Torsional Irregularity	IS 1893-2016 (Part-I) Table-5	Torsional Mode Time Period should be lesser than X and Y direction Time periods	Yes
Vertical Irregularityk	IS 1893-2016 (Part-I) Table-6 Clause-7	First Three modes together should contribute at least 65% in mass participation factor in each principal direction	Yes
		Fundamental Lateral natural periods in two principal plane directions are away from each other by at least 10%	No
Inter-Storey Drift	IS 1893-2016 (Part-I) Clause 7.11.1.1	Storey Drift shall not exceed 0.004 times the storey height for base shear with no load Factors	Yes