Modelling of 25 storey building with the specified properties using ETABS

Challenge 6 – ETABS modelling of a 25 storey building

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: Tx1">Tx1Tx1= 4.4 second Ty1">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

Answer:-

Aim:- To determine the load properties of given 25 storey building by using ETABS software.

Introduction:- Etabs is the software which is used to analyze the highrise buildings, so now we can analyze the given structure and we can get the required results by using this software.

Procedure:-

1)Plotting:-

Open the ETABS software

Select new model

Select built-in settings with

Enter the data like

Diplay units - Metric SI

Steel section data base - Indian

Steel design code - IS :800 - 2007

Concrete design code - IS:456-2000

Custom grid spacing

Edit grid data X&Y

Custom store data

Z-axis (top to bottom)

Right click on arrow mark after edit similar to

Add storey then add the number of storeys you need (here 25)

similar to select storey1 click ok.

2)Materials:-

Define

Material poperties

Add material

Edit material details

Define

Section properties

Frame sections beams

Give details (B300 x 400)

Here in this case proprty modifier should be noted for ultimate design (no need to change anything for analysis)

Modifyor show rebar

Select design type

Rebar materials

click ok

Repeat the above procedure for columns too (c500X500)

Define

Section properties

Slab sections (S150)

Add new properties (Modelling type-membrane)

Define

Load patterns

Create loads

Add EQX,EQY for seismic loads

Note:- here we need to click on addnew to save the new loads ,after that modify the lateral load settings by modifying DX,DY & soil types,zone types as mentioned in problem.

Define

Mass sources

Modify/show mass source

select specified load patterns

100% of dead load

25% of live load

100% of super dead load

As per IS code

click ok.

3)Load cases:-

Define

Load cases

For check the loads what we design

Define

Load combinations

Select concrete frame design

select convert to user combinations (editable)

click ok

4)Modelling stage:-

Quick draw columns

Choose property

Ensure it for all storeys (at right down corner)

Place the column at required position after clicking on plan view

Then it will projects on right side

For placing columns select the column and go to edit and REPLICATE and choose the distance & No.s to be repeated.

Repeat the procedure by selecting Quick draw beams (For X&Y axes)

Go to plan view select storey 1 click apply and select for similar stories

Quick draw floor/wall choose property S150 select the space between columns and beams and we can use the replicate too.

Here Base supports are pinned as default.

Select

Properties

Frame selection

B 300 X 400

Click ok

5) Loads:-

Assign

Frame loads

Distributed

Put load pattern name as wall & uniform load is 10KN/M

click apply

click ok

Select

Properties

Slab sections

S150

Select

Close

Assign

Shell loads

uniform

Load pattern name

Live load 3 kn/m^2

click apply

click ok

Select

Properties

Slab Sections

S150

Click ok

Assign

Shell

Diaaphragm

D1

Apply

Then center of mass for the floor will be automatically calculated

After all this click on Run analysis (F5)

Selected model will be saved.

The results we got are as below:-

Results:-

To get the table results or formats shpwn in above are

Tables

Analysis results

Modal info

model periods & frequencies

Add data

Criteria		Desirable solution	Excercise result
Fundamental translational Natural period	X - Direction Y - Direction	4.4 seconds 4.2 seconds	5.17 4.95
Torsional irregularity	IS:1893:2016 (part-1) table-5	Torsional mode time period should be lesser than X & Y direction time periods	Yes
Vertical irregularity	IS:1893:2016 (part-1) table-6 clause-7	First three modes together should combine at least 65% in mass partcipation factor in each principal direction	Yes
		Fundamental lateral natural periods in two principal plane directions are away from each other at least 10%	No
Inter-storey draft	IS:1893:2016 (part-1) clause-7.11.1.1	Storey drift shall not exceed 0.004 times the torey height for base shear with no load factors (4 x 10^-3)	Yes

Finally i got to know aboyt how to design and analyze a building by using ETABS software.