Modelling of 25 storey building with the specified properties using ETABS

Model a 25 storey building on ETABS with structural properties as specified below. Ground floor or plinth floor level can be taken at a height of 1.5 metres from the base. Each of the successive 25 storeys has a storey height of 3 metres.

Structural Element Sizes

• Beams : 300 × 400 mm
• Columns : 800 × 800 mm
• Slab : 150 mm thick

Material Properties

• Grade of Concrete : M30
• Grade of Steel Reinforcement Bars : Fe 415

Loading

• Dead Load on beams from infill wall : 10 kN/m (Let us assume the same for roof floor in view of parapet)
• Live load on floor : 3 kN/m2 (Let us assume the same for roof floor)

a) Buildings are assumed to be pinned at the base

b) All columns in all storey are of the same size

c) All beams in all storeys are of the same size

d) Building is located on Soil type-II and in Zone-III. Assume other factors if required.

Carry out the following exercises:

• Check if the translational fundamental natural period of vibration in both the x and y direction is approximately: Tx1Tx1= 4.4 second Ty1Ty1= 4.2 second

This check will help confirm if modelling is done correctly. Some deviations from the above values is possible (± 2%). But any major deviation will suggest an error in modelling.

• Check if the following provision in Table 5 of IS 1893 (part 1) – 2016, on torsional irregularity satisfied:

The natural period corresponding to the torsional mode of oscillation must be less than the two fundamental translational modes of oscillation along each principal plan directions.

• Check if the two provisions of clause 7 in Table 6 (shown below) of IS 1893 (part 1) – 2016, regarding vertical irregularity is satisfied

• Check if provision on inter-storey drift limitations in clause 7.11.1.1 satisfied. Please note that this check is for Serviceability Limit State and hence is for situation when stucture is subjected to unfactored seismic base shear

Aim:

To model a 25 storey building on ETABS with the given structural properties.

Procedure:

First we need to open the etabs file by searching in the windows and then double click on the icon to open the software.

once we open the file click on the new model. we can see a new window has been opened.

now click on the use built in settings. then click on the ok.

We can see a new tab asking for grid dimensions.

now click on the customize grid spacing to give grids. click on then edit grid data.

Now we can see that adding an asking for the spacing along both the axis.

now click on ok. we will redirect back to grid data. Now select customize story data.

now click on the story names and give them the names and the chanke the hight of plint as give to 1.5m.

To add the story to the data. on the left we can see an triangle right click on it so that we can see a small asking.

now click on the add story. give the no of storys. so we can see a story has been added to the tab.

We can see the added storys in the story data.

once we click on ok we can see a model has been generated for us.

now click on the befine in the ribbon tab and then click on the material properties.

now click on the add materials on the side

now choose the material properties. then click on ok

now windows will show this all properties details.

now we can see the added material in the material properties.

now we add the reinforcemnt material in the properties by selecting the rebar in the material properties.we can see the standerd rebar.

To add the material properties click on the add define and go to the section properties then click on the frame section.

now align the material properties to the frame section. adding the new material.

Now select the property type.

Give the proper dimension and the properties to the material.

now click on the modify rebar in the reinforcement. To change the rebar properties inside the beam.

Now click on the ok. so that we can see the material has been added with the properties in the section.

Add the column propeties by adding the new material again ang give the dimensions and the material type.

Now give the rebar properties by clicking on the rebar.

As we can see the materials has been added.

Now to add the slab properties click on the define and click on the sectional properties and then click on the slab to give the properties.

Now click on the add new material.

now definre the material properties in the tab and then click on ok.

After defining the properties just click on enter so that we can see the added material in the slab.

Now to define load we need to go to the define and click on the load pattern.

now give the loads patterns and click on add to add the loads.

To modify the load click on the modify lateral load and change the load pattern.

as given we need to take the soil type 2 and the and the change the zone factor.

uncheck all the other eccenticity except the x becouse we are modifying the properties with respect to the load.

now click on the EQy and define the properties to that. as per the given condition.

Now to assain the mass store data as par the standerds.

we nee to click on the define in the ribbon and click on the mass source.

now click on the add new mass source to give the properties.

now defiened the sources mass accorging to the standerds and then click on ok.

Now we need to create the load combinations. click on the define in the ribbon bar and then click on the load combinations.

click on then add default design combinations.

Now we can see the combinations in the screen.

now to draw a columns in the plan click on the quick draw colums in the left side of the screen.

Now change the dimension of the column accordingly.

as columns is same in all stories select all stories option on the right down of the screen.

now click on the points to create colums in the plan.

Now we can see that columns has been placed in all the storys now.

Now we select the quick draw beams option in the left side of the screen.

Now change the beam properties according to give in the properties browser.

Now click on the line to create the beams.

now we can see the beams has been added to the plan.

now to add the slad to the plan click on the first floor. then change the type to simmilar stories becouse we dont need the slab in all the levels.

now click on the quick draw floor in the left hand side of the window.

Now change the properties accordingly to the slab.

now click in the floor to create a slab.

now we can see slab has been added to the plan.

To assain the loads

now to select all the beams click on the select option in the ribbon bar and click on the properties and then click on the frame.

now to assain the loads click frame loads and then click on distributed frame load.

now give the values as the given loads.

now select all the slab to assain load.

So, we nee to click on the selet then go to the properties and then select the slab section.

Now to assain the load then click on the shell load then click on the uniform shell load.

Now give the properties according to the given.

now we cans see the assaigned loads.

To assaign the center of mass to the floor select all the slabs again.

now assaign the load click on assaign and then click on shell then click on the diaphragms

now cselect the diaphrame and apply and select ok.

As now we can see the center of mass has been calculated.

As everthing is done now click on the analyze in the ribbon bar.

After the completion of the analysis we can see the result in the model explorer.

Exercise analysis: